Fibrinoid and trophoblastic necrosis with massive chronic intervillositis: an extreme variant of villitis of unknown etiology

Histologic and molecular features shared between antibody-mediated rejection of kidney allografts and chronic histiocytic intervillositis support common pathogenesis

Chronic histiocytic intervillositis (CHI) is an inflammatory condition of the placenta, characterised by an abnormal, mainly macrophagic infiltrate within the intervillous space. Recent research suggests that CHI results from a 'maternal-foetal rejection' mechanism, because at least some CHI cases fulfil the criteria for antibody-mediated rejection (AMR) of kidney allografts according to the Banff classification [i.e. presence of anti-human leukocyte antigen (HLA) paternal antibodies activating the complement or foetal-specific antibodies (FSA), a macrophage-rich infiltrate, and positive C4d immunostaining]. To gain further insights into CHI pathogenesis, we aimed to refine the phenotype of the inflammatory infiltrate using a multiplex immunofluorescence technique and to compare the mRNA signatures between CHI and AMR of kidney allografts. Twelve patients with C4d+ FSA+ CHI were included in the study and compared to a control group of 5 patients without inflammatory lesions on placental examination. We developed a multiplex immunofluorescence panel to identify CD4+ and CD8+ T lymphocytes, CD68+/CD206- and CD68+/CD206+ macrophages, and NK cells in the villi and intervillous space. Molecular signatures were studied using NanoString® technology and the B-HOT panel recommended by the Banff classification for kidney allografts. Multiplex immunofluorescence revealed that the infiltrate in the intervillous space was mainly composed of CD68+/CD206- macrophages as well as a higher proportion of CD8+ lymphocytes in patients with CHI compared to controls. Densities of NK cells and CD4 T cells were very low. Molecular signatures showed an overexpression of HLA class II genes, an IFN-γ signature, and cytokine gene sets in C4d+ FSA+ CHI patients, also involved in kidney AMR. These results reinforce the paradigm of maternal-foetal rejection. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Caracteristics of women presenting with chronic histiocytic intervillositis during pregnancy: A case-control study

INTRODUCTION

Chronic Histiocytic Intervillositis (CHI) appears to be among the most severe placental diseases. Its rarity has limited our knowledge of the women in whom it occurs.

OBJECTIVE

To search for maternal characteristics linked to the existence of CHI, by first studying the current pregnancy included in the study, then their previous pregnancies.

MATERIAL AND METHODS

We conducted a monocentric case-control study between 2000 and 2020. CHI cases were diagnosed by microscopic examination of the placenta. "Low-risk" controls gave birth just before each case, whatever the outcome. "High-risk" controls benefited from placental microscopy immediately after the case examinations.

RESULTS

151 women were included in each group. CHI cases had twice as many previous pregnancies as both controls, but no more living children at home. Regarding obstetric history, fetal losses were significantly higher in CHI cases: compared to "low-risk" controls, there were more early miscarriages (20.0%, OR 2.6 [1.5;4.8]), late miscarriages (4.8%, OR 8.8 [1.1;187]) and in utero deaths (5.4%, OR 5.6 [1.7;19.8]). The risk of fetal loss does not appear to be increased in first pregnancies of CHI cases. However, differences appeared between cases and both "low-risk" and "high-risk" controls with a history of two previous miscarriages (21.7% vs 11.2%, p=0.009 or vs 9.6%, p=0.005) and the outcome of the second pregnancy (number of living children 59.7% vs 78.0%, p=0.033 or vs 63.0%, p=0.71), respectively.

CONCLUSION

Women with CHI have a more frequent history of pregnancy failure than other women. This excess fetal loss seems to occur only after the second pregnancy or after two previous miscarriages.

[Which workup should be performed after a pregnancy complicated with vasculo-placental disorder?]

Vasculo-placental disorders include pregnancy complications resulting from placental dysfunction of vascular origin, i.e. pre-eclampsia, HELLP syndrome, intrauterine growth retardation (IUGR), placental abruption and stillbirth of vascular origin. Pre-eclampsia should be investigated for antiphospholipid syndrome (APS) in case of severe pre-eclampsia and premature delivery before 34 weeks of gestation. In addition to testing for APS, pathological report of the placenta can identify some anatomical predispositions to placental vascular malperfusion, as well as chronic placental inflammatory lesions and excess fibrin deposits. The latter two are associated with IUGR and recurrent stillbirth, reflecting a dysimmune process of maternal origin. The internal medicine and obstetrics consultation, organized two months after delivery, combines the postnatal visit with an assessment of the causes of vasculo-placental disorders, and enables to inform patients about the management of future pregnancies and their cardiovascular health.

Inflammasome-targeted therapy might prevent adverse perinatal outcomes of recurrent chronic intervillositis of unknown etiology

Chronic histiocytic intervillositis of unknown origin (CHI) is a rare placental disorder associated with adverse pregnancy outcomes, frequent recurrence, and a lack of effective preventive strategies. Recent insights indicate a potential link between CHI-associated inflammatory lesions and the inflammasome pathway, suggesting innovative therapeutic avenues. Here we show a potential role of the inflammasome pathway in CHI through comprehensive transcriptomic analysis of grade 2 or 3 histopathologic CHI samples, paired with placental controls. Additionally, we present case studies of three individuals with recurrent CHI, who have undergone treatment with anakinra and colchicine throughout pregnancy, resulting in improved perinatal outcomes. Notably, all cases are characterized by the birth of healthy, full-term infants, with reduced or absent intervillositis recurrence. Placental assessment unveils heightened activation of the NLRP3-PYCARD inflammasome pathway and IL-1β processing in CHI samples, with downregulation observed in treated pregnancy samples, devoid of intervillositis. Collectively, these findings suggest a potential therapeutic role for targeting the inflammasome pathway in preventing recurrent CHI in pregnant individuals.

Virtual crossmatching reveals upregulation of placental HLA-Class II in chronic histiocytic intervillositis

Chronic histiocytic intervillositis (CHI) is a recurrent placental lesion where maternal macrophages infiltrate the intervillous space. Its cause is unknown, though due to similarities to rejected allografts one hypothesis is that CHI represents maternal-fetal rejection. Here, virtual crossmatching was applied to healthy pregnancies and those with a history of CHI. Anti-HLA antibodies, measured by Luminex, were present in slightly more controls than CHI (8/17 (47.1%) vs 5/14 (35.7%)), but there was no significant difference in levels of sensitisation or fetal specific antibodies. Quantification of immunohistochemical staining for HLA-Class II was increased in syncytiotrophoblast of placentas with CHI (Grade 0.44 [IQR 0.1-0.7]) compared to healthy controls (0.06 [IQR 0-0.2]) and subsequent pregnancies (0.13 [IQR 0-0.3]) (P = 0.0004). HLA-Class II expression was positively related both to the severity of CHI (r = 0.67) and C4d deposition (r = 0.48). There was no difference in overall C4d and HLA-Class I immunostaining. Though increased anti-HLA antibodies were not evident in CHI, increased expression of HLA-Class II at the maternal-fetal interface suggests that they may be relevant in its pathogenesis. Further investigation of antibodies immediately after diagnosis is warranted in a larger cohort of CHI cases to better understand the role of HLA in its pathophysiology.

Reproductive and treatment outcomes in chronic intervillositis of unknown etiology: A systematic review and meta-analysis

Chronic Intervillositis of Unknown Etiology (CIUE) is a rare idiopathic inflammatory disorder of the placenta. The evidence suggests an increased risk for poor obstetrical outcomes and a risk of recurrence as high as 100 %. This meta-analysis examined CIUE prevalence, recurrence, association with autoimmune disorders, reproductive outcomes, pregnancy complications, and the benefits of medical treatments. A systematic review, following PRISMA guidelines, involved a thorough search across multiple databases including Medline, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Evidence Based Medical Reviews, and Scopus. Out of 590 initially identified studies, 19 studies were included for both qualitative synthesis and meta-analysis after full-text review. Risk of bias was assessed using appropriate tools: The Risk Of Bias In Non-randomized Studies of Interventions tool was applied to twelve studies, while the Joanna Briggs Institute case series critical appraisal tool was used for seven studies. Our findings confirm that CIUE is a rare condition (0.7 %). CIUE is associated with decreased live birth rates (53 %), increased recurrent pregnancy loss (23 %), fetal loss beyond 22 weeks gestation (25 %), a higher prevalence of autoimmune diseases (14 %), and a recurrence rate of 30 % in subsequent pregnancies. Moreover, individuals with CIUE had higher rates of pregnancy complications, including gestational hypertension (19 %), intrauterine growth restriction (45 %), and preterm births (43 %). No significant improvement in live birth rate was observed among treated CIUE patients; however, caution is warranted when interpreting these findings due to the limited sample size. Future research in CIUE is crucial given its rarity and complexity.

Acute response to pathogens in the early human placenta at single-cell resolution

The placenta is a selective maternal-fetal barrier that provides nourishment and protection from infections. However, certain pathogens can attach to and even cross the placenta, causing pregnancy complications with potential lifelong impacts on the child's health. Here, we profiled at the single-cell level the placental responses to three pathogens associated with intrauterine complications-Plasmodium falciparum, Listeria monocytogenes, and Toxoplasma gondii. We found that upon exposure to the pathogens, all placental lineages trigger inflammatory responses that may compromise placental function. Additionally, we characterized the responses of fetal macrophages known as Hofbauer cells (HBCs) to each pathogen and propose that they are the probable niche for T. gondii. Finally, we revealed how P. falciparum adapts to the placental microenvironment by modulating protein export into the host erythrocyte and nutrient uptake pathways. Altogether, we have defined the cellular networks and signaling pathways mediating acute placental inflammatory responses that could contribute to pregnancy complications.

Characterizing Histopathologic Features in Pregnancies With Chronic Histiocytic Intervillositis Using Computerized Image Analysis

CONTEXT.—

Chronic histiocytic intervillositis (CHI) is a rare condition characterized by maternal immune cell infiltration into the human placenta. CHI is strongly associated with fetal growth restriction, miscarriage, and stillbirth, and knowledge of its etiology, and consequently effective treatment, is limited. Currently, diagnosis is largely subjective and varies between centers, making comparison between studies challenging.

OBJECTIVE.—

To objectively quantify and interrelate inflammatory cells and fibrin in placentas with CHI compared with controls and determine how pathology may be altered in subsequent pregnancies following diagnosis. Macrophage phenotype was also investigated in untreated cases of CHI.

DESIGN.—

Computerized analysis was applied to immunohistochemically stained untreated (index) cases of CHI, subsequent pregnancies, and controls. Index placentas were additionally stained by immunofluorescence for M1 (CD80 and CD86) and M2 macrophage markers (CD163 and CD206).

RESULTS.—

Quantification revealed a median 32-fold increase in macrophage infiltration in index cases versus controls, with CHI recurring in 2 of 11 (18.2%) subsequent pregnancies. A total of 4 of 14 placentas (28.6%) with a diagnosis of CHI did not exhibit infiltration above controls. Macrophages in index pregnancies strongly expressed CD163. There was no significant difference in fibrin deposition between index cases and controls, although subsequent pregnancies displayed a 2-fold decrease compared with index pregnancies. CD3+ T cells were significantly elevated in index pregnancies; however, they returned to normal levels in subsequent pregnancies.

CONCLUSIONS.—

In CHI, intervillous macrophages expressed CD163, possibly representing an attempt to resolve inflammation. Computerized analysis of inflammation in CHI may be useful in determining how treatment affects recurrence, and alongside pathologist expertise in grading lesion severity.

Collateral Damage in the Placenta during Viral Infection in Pregnancy: A Possible Mechanism for Vertical Transmission and an Adverse Pregnancy Outcome

In mammals, the placenta is a connection between a mother and a new developing organism. This tissue has a protective function against some microorganisms, transports nutrients, and exchanges gases and excretory substances between the mother and the fetus. Placental tissue is mainly composed of chorionic villi functional units called trophoblasts (cytotrophoblasts, the syncytiotrophoblast, and extravillous trophoblasts). However, some viruses have developed mechanisms that help them invade the placenta, causing various conditions such as necrosis, poor perfusion, and membrane rupture which, in turn, can impact the development of the fetus and put the mother's health at risk. In this study, we collected the most relevant information about viral infection during pregnancy which can affect both the mother and the fetus, leading to an increase in the probability of vertical transmission. Knowing these mechanisms could be relevant for new research in the maternal-fetal context and may provide options for new therapeutic targets and biomarkers in fetal prognosis.

SARS-CoV-2 Infection in Late Pregnancy and Childbirth from the Perspective of Perinatal Pathology

This review focuses on SARS-CoV-2 infection in placental and fetal tissues. Viremia is rare in infected pregnant women, and the virus is seldom amplified from placental tissues. Definite and probable placental infection requires the demonstration of viral RNA or proteins using in situ hybridization (ISH) and immunohistochemistry (IHC). Small subsets (1.0-7.9%, median 2.8%) of placentas of SARS-CoV-2-positive women showed definite infection accompanied by a characteristic histopathology named SARS-CoV-2 placentitis (SP). The conventionally accepted histopathological criteria for SP include the triad of intervillositis, perivillous fibrin deposition, and trophoblast necrosis. SP was shown to be independent of the clinical severity of the infection, but associated with stillbirth in cases where destructive lesions affecting more than 75% of the placental tissue resulted in placental insufficiency and severe fetal hypoxic-ischemic injury. An association between maternal thrombophilia and SP was shown in a subset of cases, suggesting a synergy of the infection and deficient coagulation cascade as one of the mechanisms of the pathologic accumulation of fibrin in affected placentas. The virus was amplified from fetal tissues in approximately 40% of SP cases, but definite fetal involvement demonstrated using ISH or IHC is exceptionally rare. The placental pathology in SARS-CoV-2-positive women also includes chronic lesions associated with placental malperfusion in the absence of definite or probable placental infection. The direct viral causation of the vascular malperfusion of the placenta in COVID-19 is debatable, and common predispositions (hypertension, diabetes, and obesity) may play a role.

SARS-CoV-2 placentitis, stillbirth, and maternal COVID-19 vaccination: clinical-pathologic correlations

Stillbirth is a recognized complication of COVID-19 in pregnant women that has recently been demonstrated to be caused by SARS-CoV-2 infection of the placenta. Multiple global studies have found that the placental pathology present in cases of stillbirth consists of a combination of concurrent destructive findings that include increased fibrin deposition that typically reaches the level of massive perivillous fibrin deposition, chronic histiocytic intervillositis, and trophoblast necrosis. These 3 pathologic lesions, collectively termed SARS-CoV-2 placentitis, can cause severe and diffuse placental parenchymal destruction that can affect >75% of the placenta, effectively rendering it incapable of performing its function of oxygenating the fetus and leading to stillbirth and neonatal death via malperfusion and placental insufficiency. Placental infection and destruction can occur in the absence of demonstrable fetal infection. Development of SARS-CoV-2 placentitis is a complex process that may have both an infectious and immunologic basis. An important observation is that in all reported cases of SARS-CoV-2 placentitis causing stillbirth and neonatal death, the mothers were unvaccinated. SARS-CoV-2 placentitis is likely the result of an episode of SARS-CoV-2 viremia at some time during the pregnancy. This article discusses clinical and pathologic aspects of the relationship between maternal COVID-19 vaccination, SARS-CoV-2 placentitis, and perinatal death.

The severity of chronic histiocytic intervillositis is associated with gestational age and fetal weight

INTRODUCTION

Chronic histiocytic intervillositis (CHI) is a rare histopathological lesion in the placenta that is associated with poor reproductive outcomes. The intervillous infiltrate consists mostly of maternal mononuclear cells and fibrin depositions, which are both indicators for the severity of the intervillous infiltrate. The severity of the intervillous infiltrate as well as the clinical outcomes of pregnancy differ between cases. Our objective is to determine the relation between the severity of the intervillous infiltrate and the clinical outcomes of CHI.

METHODS

Cases of CHI were semi-quantitatively graded based on histopathological severity scores. Hereto, CD68 positive mononuclear cells were quantified, fibrin depositions visualized by both a PTAH stain and an immuohistochemical staining, and placental dysfunction was assessed via thrombomodulin staining.

RESULTS

This study included 36 women with CHI. A higher CD68 score was significantly associated with a lower birthweight. Loss of placental thrombomodulin was associated with lower gestational age, lower birthweight, and a lower placenta weight. The combined severity score based on CD68 and PTAH was significantly associated with fetal growth restriction, and the joint score of CD68 and fibrin was associated with birthweight and placental weight.

DISCUSSION

More severe intervillous infiltrates in CHI placentas is associated with a lower birth weight and placental weight. Furthermore, this study proposes thrombomodulin as a possible new severity marker of placental damage. More research is needed to better understand the pathophysiology of CHI.

Chronic Inflammatory Placental Disorders Associated With Recurrent Adverse Pregnancy Outcome

Chronic inflammatory placental disorders are a group of rare but devastating gestational syndromes associated with adverse pregnancy outcome. This review focuses on three related conditions: villitis of unknown etiology (VUE), chronic histiocytic intervillositis (CHI) and massive perivillous fibrin deposition (MPFD). The hallmark of these disorders is infiltration of the placental architecture by maternal immune cells and disruption of the intervillous space, where gas exchange between the mother and fetus occurs. Currently, they can only be detected through histopathological examination of the placenta after a pregnancy has ended. All three are associated with a significant risk of recurrence in subsequent pregnancies. Villitis of unknown etiology is characterised by a destructive infiltrate of maternal CD8+ T lymphocytes invading into the chorionic villi, combined with activation of fetal villous macrophages. The diagnosis can only be made when an infectious aetiology has been excluded. VUE becomes more common as pregnancy progresses and is frequently seen with normal pregnancy outcome. However, severe early-onset villitis is usually associated with fetal growth restriction and recurrent pregnancy loss. Chronic histiocytic intervillositis is characterised by excessive accumulation of maternal CD68+ histiocytes in the intervillous space. It is associated with a wide spectrum of adverse pregnancy outcomes including high rates of first-trimester miscarriage, severe fetal growth restriction and late intrauterine fetal death. Intervillous histiocytes can also accumulate due to infection, including SARS-CoV-2, although this infection-induced intervillositis does not appear to recur. As with VUE, the diagnosis of CHI requires exclusion of an infectious cause. Women with recurrent CHI and their families are predisposed to autoimmune diseases, suggesting CHI may have an alloimmune pathology. This observation has driven attempts to prevent CHI with a wide range of maternal immunosuppression. Massive perivillous fibrin deposition is diagnosed when >25% of the intervillous space is occupied by fibrin, and is associated with fetal growth restriction and late intrauterine fetal death. Although not an inflammatory disorder per se, MPFD is frequently seen in association with both VUE and CHI. This review summarises current understanding of the prevalence, diagnostic features, clinical consequences, immune pathology and potential prophylaxis against recurrence in these three chronic inflammatory placental syndromes.

Placental Tissue Destruction and Insufficiency from COVID-19 Causes Stillbirth and Neonatal Death from Hypoxic-Ischemic Injury: A Study of 68 Cases with SARS-CoV-2 Placentitis from 12 Countries

CONTEXT.—

Perinatal death is an increasingly important problem as the COVID-19 pandemic continues, but the mechanism of death has been unclear.

OBJECTIVE.—

To evaluate the role of the placenta in causing stillbirth and neonatal death following maternal infection with COVID-19 and confirmed placental positivity for SARS-CoV-2.

DESIGN.—

Case-based retrospective clinico-pathological analysis by a multinational group of 44 perinatal specialists from 12 countries of placental and autopsy pathology findings from 64 stillborns and 4 neonatal deaths having placentas testing positive for SARS-CoV-2 following delivery to mothers with COVID-19.

RESULTS.—

All 68 placentas had increased fibrin deposition and villous trophoblast necrosis and 66 had chronic histiocytic intervillositis, the three findings constituting SARS-CoV-2 placentitis. Sixty-three placentas had massive perivillous fibrin deposition. Severe destructive placental disease from SARS-CoV-2 placentitis averaged 77.7% tissue involvement. Other findings included multiple intervillous thrombi (37%; 25/68) and chronic villitis (32%; 22/68). The majority (19, 63%) of the 30 autopsies revealed no significant fetal abnormalities except for intrauterine hypoxia and asphyxia. Among all 68 cases, SARS-CoV-2 was detected from a body specimen in 16 of 28 cases tested, most frequently from nasopharyngeal swabs. Four autopsied stillborns had SARS-CoV-2 identified in internal organs.

CONCLUSIONS.—

The pathology abnormalities composing SARS-CoV-2 placentitis cause widespread and severe placental destruction resulting in placental malperfusion and insufficiency. In these cases, intrauterine and perinatal death likely results directly from placental insufficiency and fetal hypoxic-ischemic injury. There was no evidence that SARS-CoV-2 involvement of the fetus had a role in causing these deaths.

The Potential Benefit of Hydroxychloroquine in Chronic Placental Inflammation of Unknown Etiology Associated with Adverse Pregnancy Outcomes

The placenta is the site of connection between maternal and fetal circulation, and the liaison is established early in pregnancy. A large variety of pregnancy complications such as preterm birth, fetal growth restriction, or pregnancy loss have placental expression and can be accompanied in some cases of acute or chronic identifiable placental inflamatory lesions. Chronic placental inflammatory (CPI) lesions include chronic villitis of unknow etiology (CVUE), chronic intervillositis of unknown etiology, CIUE (also described as chronic histiocytic intervillositis, CHI), and chronic deciduits. Hydroxychloroquine (HCQ) has been prescribed with good results during pregnancy to prevent adverse perinatal outcomes in maternal autoimmune conditions. Its success has paved the way to its use in CPI as CIUE/CHI; however, to date, there are no prospective, informatively designed, controlled studies on its value in these setting. This review aims to explore the potential role of HCQ in CPI of unknown etiology. Ideally, properly designed, probably multicentric studies should be undertaken to fully understand HCQ's role for prevention of adverse pregnancy outcomes after a chronic placental inflammation.

Chronic histiocytic intervillositis (CHI): current treatments and perinatal outcomes, a systematic review and a meta-analysis

BACKGROUND

Chronic histiocytic intervillositis (CHI) is a rare placental lesion with a high recurrence rate and poor perinatal outcomes. There are currently limited guidelines regarding the diagnosis of this condition in the index pregnancy and treatment where recurrence is suspected.

OBJECTIVE

The primary objective of this systematic review and meta-analysis was to determine the perinatal outcomes of pregnancies affected by chronic histiocytic intervillositis and to what extent they can be improved with treatment. The secondary objective was to assess the relationship between CHI lesion severity and pregnancy loss.

METHODS

A systematic search of Ovid Embase, Web of Science, Science Direct, PubMed, Ovid Medline, Google Scholar and CINAHL was carried out. Case reports, cohort, case-control and randomised controlled trials (RCT) detailing the perinatal outcomes of CHI pregnancies, both treated and untreated, were included.

RESULTS

No RCTs were identified. However, in a review population of 659 pregnancies, with additional 7 in case reports, CHI treatments included aspirin, prednisone, prednisolone, low molecular weight heparin (LMWH), hydroxychloroquine and adalimumab. A descriptive synthesis of data found mixed results for treatments in relation to live birth, miscarriage and fetal growth restriction outcomes. Furthermore, quantitative synthesis of 38 pregnancies revealed a non-significant improvement in live birth rate with CHI targeted treatment (OR 1.79 [95% CI 0.33-9.61] (p=0.50), while meta-analysis of CHI severity in line with pregnancy loss, in a sample of 231 pregnancies, revealed lower odds of pregnancy loss with less severe lesions (OR: 0.17 [0.03-0.80], p=0.03).

CONCLUSIONS

This systematic review and meta-analysis reinforce notions surrounding the insufficient evidence for CHI treatment. It also strengthens previous hypotheses detailing the positive association between CHI lesion severity and odds of pregnancy loss. Aspirin, LMWH, prednisolone, hydroxychloroquine and adalimumab are candidates with varying levels of weak to moderate evidence supporting their use. Further prospective research is required to obtain robust evidence pertaining to treatment safety and efficacy and optimal drug regimes.

SYSTEMATIC REVIEW REGISTRATION

[website], identifier CRD42021237604.

Immunomodulatory Therapy Reduces the Severity of Placental Lesions in Chronic Histiocytic Intervillositis

Chronic histiocytic intervillositis (CHI) is a rare, but highly recurrent inflammatory placental lesion wherein maternal macrophages infiltrate the intervillous space. Pregnancies with CHI are at high risk of fetal growth restriction, miscarriage or stillbirth. Presently, the diagnosis can only be made after histopathological examination of the placenta. Given its proposed immunological etiology, current treatments include aspirin, heparin, and immunomodulatory agents. However, the rationale for these medications is largely based upon small case series and reports as there is a lack of larger studies investigating treatment efficacy. Therefore, this study sought to determine whether inclusion of immunomodulatory medications was effective at reducing the severity of lesions and improving pregnancy outcomes in subsequent pregnancies. Thirty-three women with a history of CHI in at least one pregnancy (index case) were identified retrospectively through medical records. Twenty-eight participants presented with a first subsequent pregnancy and a further 11 with a second subsequent pregnancy at a specialist clinic for pregnancy after loss. Data on maternal demographics, medical history, medication, pregnancy outcome, and placental pathology was collected and compared between pregnancies. Twenty-seven (69%) subsequent pregnancies were treated with at least one or both of prednisolone and hydroxychloroquine. Inclusion of at least one immunomodulatory agent in treatment regimen resulted in an almost 25% increase in overall livebirth rate (61.5 vs. 86.2%). In women treated with immunomodulatory medication a greater proportion of placentas had reduced severity of lesions compared to those treated without (86.7 vs. 33.3%, respectively). A reduction in CHI severity was associated with a 62.3% improvement in livebirth rate compared to those where severity remained unchanged in relation to the index case. These data provide preliminary evidence that the use of immunomodulatory medication in the management of CHI improves histopathological lesions and the chance of livebirth in subsequent pregnancies. Due to CHI's rarity and ethical and feasibility issues, randomized controlled trials in affected women are challenging to conduct. As a result, collaboration between centers is required in future to increase study sample sizes and elucidate the mechanisms of hydroxychloroquine and prednisolone in reducing pathology.

Platelet alloimmunization is associated with low grade chronic histiocytic intervillositis - A new link to a rare placental lesion?

INTRODUCTION

Maternal alloimmunization against human platelet antigen (HPA)-1a has been implied to mediate both reduced birth weight and chronic placental inflammation. Fetal growth restriction is associated with different types of chronic inflammation in the placenta, mainly chronic histiocytic intervillositis and chronic villitis. The aim of this prospective study was to do a systematic examination of placentas from HPA-1a alloimmunized pregnancies, with focus on the histopathological and immunohistochemical diagnosis of variants of chronic inflammation.

MATERIAL AND METHODS

In a Polish-Norwegian study, 48 placentas were examined. The histopathology of placentas from 27 HPA-1a immunized women was compared with 21 placentas from non-immunized HPA-1a negative women (controls). In the group of alloimmunized women, ten received antenatal intravenous immunoglobulin G (IVIg). Tissue sections from formalin fixed paraffin embedded placental tissue were stained with hematoxylin and eosin and microscopically examined with focus on various types of chronic placental inflammations.

RESULTS

Chronic histiocytic intervillositis was observed in 40.7% of placentas from HPA-1a alloimmunized pregnancies, compared to none in the control group (p = 0.001). Chronic villitis of unknown etiology was more frequently found in the alloimmunized group, however this difference was not statistically significant. Maternal administration of IVIg did not seem to protect against chronic inflammatory lesions.

DISCUSSION

Placentas with detectable maternal anti-HPA-1a antibodies are associated with highly increased risk of low-grade chronic histiocytic intervillositis.

Chronic Histiocytic Intervillositis With Trophoblast Necrosis Is a Risk Factor Associated With Placental Infection From Coronavirus Disease 2019 (COVID-19) and Intrauterine Maternal-Fetal Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Transmission in Live-Born and Stillborn Infants

CONTEXT.—

The number of neonates with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is increasing, and in a few there are reports of intrauterine infection.

OBJECTIVE.—

To characterize the placental pathology findings in a preselected cohort of neonates infected by transplacental transmission arising from maternal infection with SARS-CoV-2, and to identify pathology risk factors for placental and fetal infection.

DESIGN.—

Case-based retrospective analysis by a multinational group of 19 perinatal specialists of the placental pathology findings from 2 cohorts of infants delivered to mothers testing positive for SARS-CoV-2: live-born neonates infected via transplacental transmission who tested positive for SARS-CoV-2 after delivery and had SARS-CoV-2 identified in cells of the placental fetal compartment by molecular pathology, and stillborn infants with syncytiotrophoblast positive for SARS-CoV-2.

RESULTS.—

In placentas from all 6 live-born neonates acquiring SARS-CoV-2 via transplacental transmission, the syncytiotrophoblast was positive for coronavirus using immunohistochemistry, RNA in situ hybridization, or both. All 6 placentas had chronic histiocytic intervillositis and necrosis of the syncytiotrophoblast. The 5 stillborn/terminated infants had placental pathology findings that were similar, including SARS-CoV-2 infection of the syncytiotrophoblast, chronic histiocytic intervillositis, and syncytiotrophoblast necrosis.

CONCLUSIONS.—

Chronic histiocytic intervillositis together with syncytiotrophoblast necrosis accompanies SARS-CoV-2 infection of syncytiotrophoblast in live-born and stillborn infants. The coexistence of these 2 findings in all placentas from live-born infants acquiring their infection prior to delivery indicates that they constitute a pathology risk factor for transplacental fetal infection. Potential mechanisms of infection of the placenta and fetus with SARS-CoV-2, and potential future studies, are discussed.

One-Sided Chronic Intervillositis of Unknown Etiology in Dizygotic Twins: A Description of 3 Cases

Chronic intervillositis of unknown etiology (CIUE) is a rare, poorly understood, histopathological diagnosis of the placenta that is frequently accompanied by adverse pregnancy outcomes including miscarriage, fetal growth restriction, and intrauterine fetal death. CIUE is thought to have an immunologically driven pathophysiology and may be related to human leukocyte antigen mismatches between the mother and the fetus. Dizygotic twins with one-sided CIUE provide an interesting context to study the influence of immunogenetic differences in such cases. The main immune-cell subsets were investigated using immunohistochemistry. We identified three dizygotic twin pregnancies in which CIUE was present in only one of the two placentas. Two of the pregnancies ended in term delivery and one ended in preterm delivery. Presence of CIUE was correlated with lower placental weight and lower birthweight. Relative number of CD68, CD56, CD20, and CD3 positive cells were comparable between co-twins. The presence of one-sided CIUE in dizygotic twin pregnancy was associated with selective growth restriction in the affected twin. This suggests a unique fetal immunogenetic contribution to the pathogenesis of CIUE. Further study of dizygotic and monozygotic placentas affected by CIUE could identify new insights into its pathophysiology and into the field of reproductive immunology.

Chronic histiocytic intervillositis: A breakdown in immune tolerance comparable to allograft rejection?

Chronic histiocytic intervillositis (CHI) is a pregnancy disorder characterized by infiltration of maternal macrophages into the intervillous space of the human placenta, often with accompanying perivillous fibrin deposition. CHI is associated strongly with foetal growth restriction and increased risk of miscarriage and stillbirth. Although rare, affecting 6 in every 10 000 pregnancies beyond 12 weeks' gestation, the rate of recurrence is high at 25%-100%. To date, diagnosis of CHI can only be made post-delivery upon examination of the placenta due to a lack of diagnostic biomarkers, and criteria vary across publications. No treatment options have shown proven efficacy, and CHI remains a serious obstetric conundrum. Although its underlying aetiology is unclear, due to the presence of maternal macrophages and the reported increased incidence in women with autoimmune disease, CHI is hypothesized to be an inappropriate immune response to the semi-allogeneic foetus. Given this lack of understanding, treatment approaches remain experimental with limited rationale. However, there is recent evidence that immunosuppression and antithrombotic therapies may be effective in preventing recurrence of associated adverse pregnancy outcomes. With similarities noted between the pathological features of CHI and acute rejection of solid organ transplants, further investigation of this hypothesis may provide a basis for tackling CHI and other immune-related placental conditions. This review will explore parallels between CHI and allograft rejection and identify areas requiring further confirmation and exploitation of this comparison.

Identification of key signaling pathways induced by SARS-CoV2 that underlie thrombosis and vascular injury in COVID-19 patients

The SARS-CoV-2 pandemic has led to hundreds of thousands of deaths and billions of dollars in economic damage. The immune response elicited from this virus is poorly understood. An alarming number of cases have arisen where COVID-19 patients develop complications on top of the symptoms already associated with SARS, such as thrombosis, injuries of vascular system, kidney, and liver, as well as Kawasaki disease. In this review, a bioinformatics approach was used to elucidate the immune response triggered by SARS-CoV-2 infection in primary human lung epithelial and transformed human lung alveolar. Additionally, examined the potential mechanism behind several complications that have been associated with COVID-19 and determined that a specific cytokine storm is leading to excessive neutrophil recruitment. These neutrophils are directly leading to thrombosis, organ damage, and complement activation via neutrophil extracellular trap release.

Trophoblast damage with acute and chronic intervillositis: disruption of the placental barrier by severe acute respiratory syndrome coronavirus 2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was demonstrated in the placenta; however, the data on the prevalence of placental infection and associated histopathology are limited. To identify the frequency and features of SARS-CoV-2 involvement, we performed a clinicopathologic analysis of 75 placental cases from women infected at the time of delivery and 75 uninfected controls. Placental samples were studied with anti-SARS-CoV-2 immunohistochemistry and/or in situ hybridization. Positive results were confirmed by electron microscopy and quantitative reverse-transcription polymerase chain reaction (qRT-PCR). During delivery, only one woman had symptoms of coronavirus disease 2019, six women reported previous symptoms, and 68 women were asymptomatic. All neonates tested negative for SARS-CoV-2 as per nasopharyngeal swab PCR results. Obstetric histories were unremarkable in 29 of 75 SARS-CoV-2-positive and 8 of 75 SARS-CoV-2-negative women. Placental examination was normal in 12 of 75 infected and 3 of 75 uninfected subjects, respectively. In the remaining cases, placental pathology correlated with obstetric comorbidities without significant differences between SARS-CoV-2-positive and SARS-CoV-2-negative women. SARS-CoV-2 was identified in one placenta of an infected, but asymptomatic, parturient. Viral staining was predominantly localized to the syncytiotrophoblast (STB) which demonstrated marked damage accompanied by perivillous fibrin deposition and mixed intervillositis. A significant decrease of viral titers was detected in the attached umbilical cord compared with the villous parenchyma as per qRT-PCR. SARS-CoV-2 is seldom identified in placentas of infected women. Placental involvement by the virus is characterized by STB damage disrupting the placental barrier and can be seen in asymptomatic mothers without evidence of vertical transmission.

Chronic Intervillositis of Unknown Etiology: Development of a Grading and Scoring System That Is Strongly Associated With Poor Perinatal Outcomes

Chronic intervillositis of unknown etiology (CIUE) is a rare placental disease characterized by intervillous infiltration of maternal macrophages and associated with poor pregnancy outcomes and a high risk of recurrence in subsequent pregnancies. Its pathophysiology remains unclear and prognostic factors have not yet been established. In addition, clear relationships between the histologic extent of lesions and the severity of perinatal outcomes have not been demonstrated. Our objectives were to validate a CIUE classification system based on the gradation of macrophagic infiltration of the intervillous space, and to attempt to correlate these results with perinatal outcomes. For this multicenter retrospective study, 3 pathologists reviewed all cases diagnosed with "intervillositis" between 1997 and 2018. Confirmed CIUE cases were semiquantitatively graded based on the percentage of macrophagic infiltrate in the intervillous space: grade 1 (5% to 10%), grade 2 (10% to 50%), and grade 3 (>50%). Multiple pregnancies and pregnancies with medical follow-up completed outside of the study centers were excluded. In total, 122 cases of CIUE in 102 patients were included in the study. Microscopic classification based on one criterion was easy to perform, and interobserver correlation was good. Grade 3 infiltration was strongly associated with poor perinatal outcomes and fetal growth restriction (P<0.0001). After delivery, only 16.1% of newborns from the grade 3 CIUE group were alive, compared with 59% from the grade 2 and 86.5% from the grade 1 group (P=0.0002). Recurrence risk was associated with CIUE gradation of the index case (P=0.004), with 95% of recurrent CIUE cases being from patients with grades 2 and 3 CIUE. In this study, conducted with the largest CIUE cohort to date, a classification based only on the degree of macrophagic infiltration of the intervillous space was validated, and this classification was shown to be strongly associated with poor perinatal outcomes and risk of recurrence.

Placental Pathology of COVID-19 with and without Fetal and Neonatal Infection: Trophoblast Necrosis and Chronic Histiocytic Intervillositis as Risk Factors for Transplacental Transmission of SARS-CoV-2

The mechanism(s) by which neonates testing positive for coronavirus disease 2019 (COVID-19) acquire their infection has been largely unknown. Transmission of the etiological agent, SARS-CoV-2, from mother to infant has been suspected but has been difficult to confirm. This communication summarizes the spectrum of pathology findings from pregnant women with COVID-19 based upon the infection status of their infants and addresses the potential interpretation of these results in terms of the effects of SARS-CoV-2 on the placenta and the pathophysiology of maternal-fetal infection. Placentas from pregnant women with COVID-19 and uninfected neonates show significant variability in the spectrum of pathology findings. In contrast, placentas from infected maternal-neonatal dyads are characterized by the finding of mononuclear cell inflammation of the intervillous space, termed chronic histiocytic intervillositis, together with syncytiotrophoblast necrosis. These placentas show prominent positivity of syncytiotrophoblast by SARS-CoV-2, fulfilling the published criteria for transplacental viral transmission as confirmed in fetal cells through identification of viral antigens by immunohistochemistry or viral nucleic acid using RNA in situ hybridization. The co-occurrence of chronic histiocytic intervillositis and trophoblast necrosis appears to be a risk factor for placental infection with SARS-CoV-2 as well as for maternal-fetal viral transmission, and suggests a potential mechanism by which the coronavirus can breach the maternal-fetal interface.

The transmembrane G protein-coupled CXCR3 receptor-ligand system and maternal foetal allograft rejection

Chronic placental inflammatory lesions lead to poor obstetric outcomes. These lesions often proceed undetected until examination of placental tissues after delivery and are mediated by CXCR3, a seven-transmembrane G protein-coupled receptor, and its chemokine ligands - CXCL9, CXCL10 and CXCL11. CXCR3-chemokine ligand interaction disrupts feto-maternal immune tolerance and activate obnoxious immunological responses similar to transplant rejection and graft-versus-host disease. The resultant chronic inflammatory responses manifest in different parts of the placenta characterised by the presence of incompatible immunocompetent cells from the feto-maternal unit i.e. maternal CD8⁺ T cells in the chorionic membrane or plate (chronic chorioamnionitis); foetal Hofbauer cells and maternal CD8⁺ T cells in the chorionic villous tree (villitis of unknown aetiology); maternal CD8⁺ T and plasma cells in the basal plate (chronic deciduitis); and maternal CD8⁺ T cells, histiocytes and T regulatory cells in the intervillous space (chronic intervillositis). This review critically examines how the CXCR3-chemokine ligand interaction disrupts feto-maternal immune tolerance, initiates a series of chronic placental inflammatory lesions, and consequently activates the pathways to intrauterine growth restriction, stillbirth, spontaneous abortion, preterm prelabour rupture of membranes, preterm labour and birth. The possibility of interrupting these signalling pathways through the use of CXCR3 chemokine inhibitors to prevent adverse reproductive sequelae as well as the potential clinical utility of CXCR3 chemokines as non-invasive predictive clinical biomarkers are also highlighted.

Diagnosis of amyopathic dermatomyositis after two intrauterine fetal deaths

Chronic histiocytic intervillositis (CHIV) is an uncommon condition, characterized by an infiltrate of mononuclear cells of maternal origin in the intervillous space that has been related to placenta insufficiency and poor perinatal outcomes. The aetiology is unclear, although maternal immunological aggression toward fetal tissues has been proposed. Dermatomyositis (DM) is a multisystem autoimmune inflammatory myopathy. Different autoantibodies have been associated with particular clinical phenotypes; presence of anti-melanoma differentiation-associated gen 5 (MDA5) antibody has been associated with rapidly progressive interstitial lung disease and severe skin lesions, none of which the woman had. Described here is a case of a woman diagnosed with amyopathic DM with positive anti-MDA5 antibodies after two intrauterine fetal deaths. Pathological examination of the placenta in both pregnancies showed CHIV. The presence of a potential relationship between both processes is discussed.

Adverse perinatal outcomes of chronic intervillositis of unknown etiology: an observational retrospective study of 122 cases

Our study aimed to assess perinatal outcomes and recurrence rate of Chronic Intervillositis of Unknown Etiology (CIUE). We conducted an observational retrospective study in a tertiary care university hospital in France from January 1, 1997 to July 31, 2018. 122 pregnancies (102 women) with CIUE were included. Cases of the Department of Histopathology placenta database were re-analysed independently by three pathologists specializing in fetal pathology. Diagnosis of CIUE was confirmed according to: (1) the presence of cellular infiltrate in the intervillous space, (2) ~ 80% of the mononuclear cells in the intervillous space positive for CD68, (3) infiltration occupying at least 5% of the intervillous space, and (4) no clinical or histopathological sign of infection. Outcomes of pregnancies with CIUE (miscarriages, stillbirths, terminations of pregnancy, live birth with or without prematurity or fetal growth restriction) and proportion of CIUE recurrence were analysed. The lost pregnancies comprised 17 (13.9%) miscarriages, 17 (13.9%) stillbirths, and 18 (14.8%) terminations of pregnancy. Of the 70 (57.4%) pregnancies that led to a live birth, 38 (54.3%) new-borns were premature and 50 (72.5%) exhibited fetal growth restriction. Among the 102 women, 23 subsequently became pregnant, half of whom (n = 11) developed recurrent CIUE. CIUE was associated with high rates of adverse perinatal outcomes, including pregnancy loss, fetal growth restriction, and preterm birth with a risk of recurrence nearly 50%.

Clinical outcomes in chronic intervillositis of unknown etiology

INTRODUCTION

Chronic intervillositis of unknown etiology (CIUE) is a histopathological lesion of the placenta that is frequently accompanied by unfavourable pregnancy outcomes, e.g. miscarriage, fetal growth restriction (FGR) and intrauterine fetal death. Earlier described case series and cohorts have been based on diverse diagnostic criteria of CIUE. To improve our understanding of clinical outcomes associated with CIUE, we report the obstetric and perinatal outcomes in a cohort based on the recently described diagnostic criteria.

METHODS

CIUE is defined as an infiltrate occupying 5% or more of the intervillous space with approximately 80% of mononuclear cells positive for CD68 in the absence of an infection. Thirty-eight cases were included. Also previous and subsequent pregnancies were described.

RESULTS

Pregnancies accompanied by CIUE frequently resulted in FGR (51.6%) and pre-term birth (55.3%). Twenty-nine out of 38 pregnancies (76.3%) with CIUE resulted in a living baby. Women with CIUE frequently have had a miscarriage (16/38; 42%). Four-teen subsequent pregnancies in 8 women resulted in 2 miscarriages, 2 terminations of pregnancy for FGR, 1 early neonatal death and 9 living babies (9/14; 64.3%). Histopathologically confirmed CIUE recurred in 5 out of 10 subsequent pregnancies. Two pregnancies with recurrent CIUE were terminated, one pregnancy ended in a late miscarriage and another resulted in term birth complicated by FGR. Recurrent CIUE can also be accompanied by an uncomplicated pregnancy (1/5; 20%).

CONCLUSION

This study provides additional insight into the clinical phenotype of CIUE and emphasises the need for further research to understand the pathophysiology behind different pregnancy outcomes in CIUE.

Is chronic histiocytic intervillositis a severe placental disease? A case-control study

INTRODUCTION

Chronic histiocytic intervillositis (CHI) is a placental disease that has been associated with unfavorable obstetric outcomes in small, noncomparative series. The objective was to measure the excess risk of adverse obstetric outcomes associated with the discovery of CHI after birth.

METHODS

Retrospective single-center case-control study from 2000 through 2016. The case patients had a CHI diagnosis after a pathology analysis of the placenta. Two types of controls were defined for each case: low-risk control women were those who gave birth in our hospital immediately before each case patient, and the high-risk controls were the next women after each case for whom microscopic examination of the placenta was indicated.

RESULTS

We observed 111 cases of CHI during the study period. Compared with the 111 low-risk controls, the cases had a significantly higher frequency of late miscarriages (5.4 vs 0.0%, p < .03), small for gestational age (SGA) babies <3rd centile (70.4 vs 0.9%, p < .001, OR 140, 95% CI, 19.9-2800), and in utero deaths (35.1 vs 0.9%, p < .001, OR 59.6, 95% CI 8.5-1192), with significantly fewer children surviving to discharge (54.9 vs 99.1%, p < .001, OR 0.01, 95% CI, 0.00-0.08). All of these factors also differed significantly compared with the high-risk women (severe SGA: OR 3.7, 95% CI 1.9-7.0; in utero death: OR 4.1, 95% CI 1.9-8.7; children surviving to discharge: OR 0.27, 95% CI, 0.14-0.52).

DISCUSSION

Even compared with high-risk pregnancies, CHI is a severe placental disease associated with a substantial excess rate of late miscarriages, severe SGA and in utero death.

CD39 downregulation in chronic intervillositis of unknown etiology

Chronic intervillositis of unknown etiology (CIUE) is a rare placental lesion associated with infiltration of mononuclear inflammatory cells into the intervillous space, poor perinatal outcomes (intrauterine fetal demise or fetal growth restriction), and high rates of recurrence. CD39 is the ectonucleotidase that protects tissues from inflammatory stress and cell injury, which is localized on the surface of villi in normal placentas; however, its expression and role in CIUE are unknown. The aims of this retrospective study were to determine the expression of CD39 in CIUE and its significance in pregnancy outcomes. We compared the number of CD68- and CD3-positive cells, CD39 expression, and complement 4d (C4d) and fibrin deposition in placental tissues from patients with CIUE (n = 22) and gestational age-matched controls (n = 20), and between CIUE pregnancies with poor and good outcomes. The numbers of CD68- or CD3-positive cells were significantly higher (P < 0.0001), whereas CD39 expression on the surface of villi and endothelial cells of the stem villi was significantly lower in the CIUE group than that in controls (45% vs. 95%, P < 0.0001 and 77% vs. 96%, P < 0.001, respectively). C4d and fibrin deposition were also significantly increased in CIUE compared with those of controls. Furthermore, CD39 downregulation and the number of CD68 cells were strongly associated with poor pregnancy outcomes (P < 0.01 and P < 0.05, respectively), but other histological parameters (CD3, C4d, and fibrin) did not show this association. Our study suggests that CD39 downregulation is a useful marker of CIUE and is associated with poor pregnancy outcomes in patients with CIUE.

Complement receptor-associated CD163+/CD18+/CD11c+/CD206-/CD209- expression profile in chronic histiocytic intervillositis of the placenta

INTRODUCTION

Chronic histiocytic intervillositis of unknown etiology (CIUE) is a non-infectious, most probably immunologic placenta lesion. CIUE is associated with recurrent miscarriage, intrauterine growth restriction and stillbirth. Among the pathologic-anatomic defined placental lesions this entity displays the highest risk of recurrence in following pregnancies (about 67-100%). The histiocytic cells accumulate in the placental blood space but do not infiltrate into the villi or decidua. Sparsely known is the expression profile of these intervillous cells regarding histiocytic markers.

METHODS

We analysed 5-22 markers by immunohistochemistry in a total of 41 placenta samples and evaluated decidual, villous and intervillous histiocytic cells.

RESULTS

In CIUE, intervillous CD163⁺ histiocytes over-express CD11c/CD18 and down-regulate CD206/CD209, while CD163⁺ decidual and Hofbauer cells show low CD11c/CD18 and higher CD206/CD209 protein expressions.

DISCUSSION

CD163 expression indicates a M2-like polarisation. CD11c and CD18 form the complement receptor 4 which could be related to a complement mediated trigger for aberrant cell accumulation in CIUE.

Placental pathologic lesions with a significant recurrence risk - what not to miss!

Here, we review three important placental pathologies with significant clinical implications and recurrence risks. They are, in order of most to least frequently seen, villitis of unknown etiology, chronic histiocytic intervillositis, and massive perivillous fibrin deposition (also known as maternal floor infarction). These entities occur in both preterm and term gestations and are observed more frequently with maternal and obstetric disorders including prior pregnancy loss, hypertension/preeclampsia, and autoimmune disease. They are associated with, and probably the cause of, significant perinatal morbidity and mortality including intrauterine growth restriction, fetal and neonatal demise, and fetal/neonatal neurocompromise (seizures and cerebral palsy). All three entities have high recurrence risks, with recurrence rates ranging from 34 to 100%. The histologic features of villitis of unknown etiology, chronic histiocytic intervillositis, and massive perivillous fibrin deposition are described herein. We discuss the clinical associations and suggest the subsequent clinical and pathological evaluation. Hypotheses as to the biology of these lesions are reviewed.

Towards standardized criteria for diagnosing chronic intervillositis of unknown etiology: A systematic review

Chronic intervillositis of unknown etiology (CIUE) is a poorly understood, relatively rare condition characterized histologically by the intervillous infiltration of mononuclear cells in the placenta. Clinically, CIUE is associated with poor pregnancy outcome (e.g., impaired fetal growth, preterm birth, fetal death) and high risk of recurrence in subsequent pregnancies. Because CIUE is not defined consistently, it is essential to clearly define this condition. We therefore review the published definitions of CIUE. In addition, we provide an overview of the reviewed histopathological and maternal characteristics, obstetric features, and pregnancy outcomes. Medical publication databases were searched for articles published through February 2017. Eighteen studies were included in our systematic review. The sole inclusion criterion used in all studies was the presence of intervillous infiltrates. Overall, CIUE was characterized by adverse pregnancy outcome. Miscarriage occurred in 24% of cases, with approximately half of these miscarriages defined as late. Impaired growth was commonly observed, 32.4% of pregnancies reached term, and the live birth rate was 54.9%. The high recurrence rate (25.1%) of the intervillous infiltrates in subsequent pregnancies underscores the clinical relevance of CIUE, the need for increased awareness among pathologists and clinicians, and the need for further research. Criteria for the diagnosis of CIUE are proposed and a Delphi study could be used to resolve any controversy regarding these criteria. Future studies should be designed to characterize the full clinical spectrum of CIUE.

Chronic histiocytic intervillositis in three consecutive pregnancies in a single patient: Differing clinical results and pathology according to treatment used

Chronic histiocytic intervillositis (CHI) is an extremely rare pathological condition but is strongly associated with severe obstetric complications and has a high recurrence rate. The management of this condition has not yet been established. We describe herein the occurrence of CHI in the late second-third trimester in each of three consecutive pregnancies in a single patient with four previous consecutive early miscarriages. In this patient, each of the three complicated pregnancies was managed with one of the following, respectively: low-dose aspirin; heparin plus low-dose aspirin; and prednisolone plus low-dose aspirin. CHI was histologically confirmed in all three pregnancies, but the clinical results and pathology (e.g. extent of histiocytic infiltration) in each pregnancy clearly differed with treatment. Both combination treatments eventuated in a live birth. Immunosuppressive therapy seemed to produce better clinical results by restricting the extent of the affected areas. The elevated alkaline phosphatase associated with the CHI was assumed to have no clinical prognostic value.

Successful pregnancy following treatment of recurrent chronic histiocytic intervillositis

Chronic histiocytic intervillositis (CHI) is a rare placental lesion associated with adverse obstetric outcomes and high recurrence rate. We report a case of six consecutive pregnancies in one woman, where CHI was detected following an intrauterine death in the fifth pregnancy, after being missed in four earlier losses. The successful sixth pregnancy was treated with a combination of immunosuppressive and antithrombotic agents. While low-molecular-weight heparin (LMWH) and aspirin had been shown to improve pregnancy outcome in recurrent pregnancy loss, there was limited evidence of improved outcome in CHI. It has been suggested that CHI may result from a maternal immunological process and there have been a few reports of the use of corticosteroids because of this possibility, though without convincing evidence of efficacy. We too tried a corticosteroid, in combination with LMWH and aspirin. Comparative histopathological analysis of the placentae supported post-treatment effectiveness of our intervention strategy.

Perinatal prognosis of pregnancies complicated by placental chronic villitis or intervillositis of unknown etiology and combined lesions: About a series of 178 cases

INTRODUCTION

The objective of this work was to evaluate and compare perinatal outcomes of pregnancies complicated by placental chronic intervillositis (CIUE) or villitis (CVUE) of unknown etiology and combined lesions.

METHODS

Retrospective study of all cases of significant CVUE and CIUE occurring during a 12-year period in a university tertiary hospital center. Multiple pregnancies, infectious and medical termination of pregnancies (TOP) without intra-uterine growth restriction (IUGR) were excluded.

RESULTS

178 placentas were affected (78 cases of CVUE, 24 cases of CIUE and 76 cases of combined lesions involving both villitis and intervillositis) including 12 cases of recurrence. A disorder of fetal growth was found in 73% of cases and we noted 9.5% of cases of abortion. The rate of IUGR appeared to be significantly higher in case of CIUE with a fetal death risk five times higher. These complications seems to be related to more diffuse inflammatory infiltrates (p < 0.05). CVUE was associated with a significant morbidity with 42% of severe IUGR and severe alterations of umbilical artery Doppler in nearly one third of cases. Caesarean section was important (54.8%). Sixty-one percent of newborns were hospitalized and 11.4% in neonatal reanimation. In case of combined lesions, fetal outcomes appeared relatively close to those of CVUE. CVUE could recur in more severe forms or as CIUE with an increased risk for the fetus. Clinicoanatomic correlations were noted.

DISCUSSION

Observation of recurrence of CVUE on CIUE or combined lesions and similar phenotypic characteristics of the infiltrates suggest that they could be two different stages of a same disease. CVUE remains a disease to be considered as serious. Association of small lesions of intervillositis does not change the prognosis. The severity of histological lesions and the initial obstetrical accident could be discriminatory to identify patients at risk of serious recurrence. Harmonized classification will be required.

CONCLUSIONS

This study confirms the higher morbidity of CIUE compared to CVUE but shows the necessity of monitoring pregnancies following an episode of CVUE, which are still at risk of serious and recurrent complications.

Maternal Floor Infarction and Massive Perivillous Fibrin Deposition

Maternal floor infarction (MFI) and massive perivillous fibrin deposition (MPVFD) are pathologically overlapping placental disorders with characteristic gross and shared light microscopic features of excessive perivillous deposition of fibrinoid material. Although rare, they are associated with high rates of fetal growth restriction, perinatal morbidity and mortality, and risks of recurrence with fetal death. The cause of the extensive fibrinoid deposition is unknown, but evidence supports involvement of maternal alloimmune or autoimmune mechanisms. This article presents an updated discussion of features, placental histopathologic differential diagnosis, possible causes, clinical correlates, and adverse outcomes of the MFI/MPVFD spectrum.

Significance of C4d Immunostaining in Placental Chronic Intervillositis

Deposition of the complement split product C4d is a phenomenon studied extensively as a marker for complement activation in antibody-mediated transplant rejection. C4d also is observed in placental disease processes including spontaneous abortion, infarct, and villitis of unknown origins. Massive chronic intervillositis is a rare placental abnormality associated with increased risk of growth restriction, fetal death, and recurrent fetal loss. In this study, we evaluated C4d immunostaining in placentas with accumulation of intervillous monocytes with and without villitis. Archived placentas from Kosair Children's Hospital (Louisville, KY) and Seattle Children's Hospital (Seattle, WA) were selected and divided into 4 groups, 16 cases of intervillositis with complicated pregnancy, 15 cases of uncomplicated intervillositis, 20 cases of complicated villitis, and 13 cases of uncomplicated villitis, all with varying degrees of monocytic cells in the intervillous space. Representative specimen blocks were immunohistochemically stained for C4d. The percentage of positive staining of the microvillous surface of the syncytiotrophoblast was scored by five pathologists, and the following consensus score was determined: 0  =  0% to 5%; 1  =  5% to 25%; 2  =  25% to 75%; and 3 ≥ 75%. C4d immunostain localized to the microvillous border of syncytiotrophoblast in many of the placentas. C4d staining was more strongly associated with intervillositis than with villitis (odds ratio: 6.3; confidence interval: 2.1-18.7; P  =  0.001).

Chronic villitis of unknown etiology and massive chronic intervillositis have similar immune cell composition

INTRODUCTION

Chronic villitis of unknown etiology (CVUE) and massive chronic intervillositis (MCI) are placental lesions associated with infiltration of mononuclear cells in the chorionic villi and the intervillous spaces, respectively. It is not well known whether immune cells in CVUE and MCI have similar phenotypic characteristics.

METHODS

A cross-sectional study of third trimester placentas was conducted to identify immune cell subpopulations in CVUE and MCI (n = 17/group). CVUE was diagnosed with H&E staining and antibody to CD3 in serial sections; and MCI, by the presence of massive infiltration of mononuclear cells in the intervillous spaces. Immune cells, ICAM-1 expression and nuclear factor κB (NF-κB) activation were determined immunohistochemically.

RESULTS

CVUE and MCI showed similar infiltrates, mainly CD68+ and CD3+ cells. Most cells (>80%) were CD45RB+, and one third were CD45RO+ in both lesions. There were slightly more CD8+ than CD4+ cells in both CVUE and MCI. More than 90% of cells in CVUE and MCI were ICAM-1+ with NFκB nuclear localization. Syncytiotrophoblast ICAM-1 expression was significantly (p < 0.001) higher in MCI (mean of 81.0; range of 71.6-86.0) than in CVUE (52.4; 36.4-59.4) or normal placentas (0.2; 0.0-0.6). Both, failure of physiologic transformation of spiral arteries and placental atherosclerosis-like lesions of atherosis were significantly more frequent in MCI than in CVUE or normal placentas (p = 0.044 and p = 0.007, respectively).

DISCUSSION

These finding suggest that MCI and CVUE have very similar infiltration of immune cells although MCI has more severe placental lesions.

Expression of Toll-Like Receptors in Chronic Histiocytic Intervillositis of the Placenta

Chronic histiocytic intervillositis of the placenta (CHI) shows monocytic/histiocytic infiltration of the intervillous space. Placental malaria has a CHI-like histopathology and induces an aberrant expression of Toll-like receptors (TLR) 3, 7-9. We hypothesized that, similar to placental malaria, CHI could be associated with increased TLR expression. TLR1-10 and other inflammation-associated factors were analyzed by real-time PCR and immunohistochemistry. A total of 31 formalin-fixed and paraffin-embedded placenta samples were evaluated: CHI (n = 9), and for control purposes, villitis of unknown etiology (VUE, n = 8) and placentas without inflammation (n = 14). CHI shows increased expression of monocytic TLR1, a receptor which is involved in bacterial lipopolysaccharide (LPS)-induced inflammation. This could indicate a TLR1-mediated immune mechanism in the placenta (e.g. triggered by transient, clinically inapparent maternal bacteraemia) which leads to massive monocytic/histiocytic accumulation in the intervillous space. The increased expression of TLR1 with no increased expression of TLR3 and TLR7-9 is different from that in malaria.

Chronic histiocytic intervillositis: outcome, associated diseases and treatment in a multicenter prospective study

Introduction: In this prospective multicenter study, we aimed to describe (1) the outcome of pregnancy in the case of previous chronic histiocytic intervillositis (CHI), (2) the immunological findings and associated diseases, (3) the treatments, and (4) the factors associated with pregnancy loss.

METHODS

We prospectively included all patients with a prior CHI with ongoing pregnancy between 2011 and 2013.

RESULTS

Twenty-four women (age 34±5 years) were included in this study. An autoimmune disease was present in seven (29%) cases. Twenty-one prospective pregnancies were treated. The number of live births was more frequent comparatively to the previous obstetrical issues (16/24 versus 24/76; p=0.003). Most of the pregnancies were treated (88%), whereas only 13% of previous pregnancies were treated (p<0.05). No difference was found with respect to the pregnancy outcome in the different treatment regimens. In univariate analyses, a prior history of intrauterine death and intrauterine growth restriction and the presence of CHI in prospective placentas were associated with failure to have a live birth.

DISCUSSION

In this multicenter study, we show the frequency of the associated autoimmune diseases in CHI, as well as the presence of autoantibodies without characterized autoimmune disease. The number of live births increased from 32% to 67% in the treated pregnancies. Despite the treatment intervention, the risk of preterm delivery remained at 30%. Last, we show that the recurrence rate of an adverse pregnancy outcome persisted at 30% despite treatment intervention.

CONCLUSION

CHI is associated with high recurrence rate and the combined regimen seems to be necessary, in particular, in the presence of previous intrauterine death.

An immunological basis for chronic histiocytic intervillositis in recurrent fetal loss

PROBLEM

Chronic histiocytic intervillositis (CHIV) is a rare type of placental pathology that is associated with reproductive loss at all gestational ages. The aim of the study was to investigate the relationship between the severity of CHIV and the outcome of pregnancy and to compare the immune response between CHIV patients and controls to explore an immunological origin of CHIV.

METHOD OF STUDY

Microscopic slides were reviewed and scored according to a previously published grading system in 30 pregnancies of 22 CHIV patients. Partner-specific mixed lymphocyte reactions, cytotoxic T-lymphocyte precursor frequencies (CTLpf), and anti-HLA antibodies were determined in four patients and seven controls.

RESULTS

Higher CHIV scores are associated with worse pregnancy outcome. CHIV patients demonstrated a higher CTLpf against their partner compared to non-complicated pregnancies (P = 0.03). The CTLpf was extremely high in 75% of the patients. Antipaternal HLA antibodies were only present in 75% of the CHIV patients compared to none of the controls (P = 0.02).

CONCLUSION

CHIV scores seem to be associated with the severity of adverse pregnancy outcome. High antipaternal cellular (T-cell) and humoral (B-cell) response to partner-specific CTLpf and the presence of anti-HLA antibodies directed to the partner suggest an immunologic origin of CHIV.

Villitis of Unknown Etiology and Massive Chronic Intervillositis

Villitis of unknown etiology (VUE) is a common lesion affecting from 6.6% to 33.8% of third-trimester placentas. VUE needs to be distinguished from villitis of infectious etiology, most commonly cytomegalovirus and syphilis. Clinically, this lesion is associated with intrauterine growth retardation, intrauterine fetal demise, fetal neural impairment, maternal alloimmune and autoimmune disease, and maternal hypertension. It has a tendency to recur in subsequent pregnancies. Massive chronic intervillositis (MCI), also known as chronic histiocytic intervillositis, is a rare lesion that has an unclear relationship with VUE. MCI is associated with recurrent abortions.