Multidisciplinary guidelines for initial evaluation of complicated lymphatic anomalies-expert opinion consensus

The application of non-enhanced magnetic resonance thoracic ductography combined with magnetic resonance abdominopelvic scanning in the diagnosis of chylous leakage of the female reproductive system

OBJECTIVE

To explore the value of non-enhanced magnetic resonance thoracic ductography (NMRTD) combined with MR abdominopelvic scanning in the diagnosis of chylous leakage of the female reproductive system.

METHODS

A retrospective analysis was conducted on the multimodal imaging data from non-enhanced magnetic resonance thoracic ductography (NMRTD), direct lymphangiography (DLG), and abdominopelvic magnetic resonance imaging (MRI) for 18 female patients with reproductive system chylous leakage. Among these patients, 7 had vaginal chylous leakage, 10 had vulvar cutaneous chylous leakage, and 1 had both conditions.The rate of successful visualization of the thoracic duct, the consistency of the drainage directions of the outlet of the thoracic duct, and the degree of visualization of each segment of the thoracic duct by NMRTD and DLG were analyzed. A retrospective analysis was performed on the abnormal manifestations of abdominopelvic MR.

RESULTS

NMRTD had a significant advantage over DLG in terms of successful visualization of the thoracic duct (94.4% vs. 66.7%, P = 0.035). The display of the drainage directions in the outlet area of the thoracic duct by the two methods showed excellent consistency (kappa value = 0.815) in 12 patients whose outlet areas were visualized by both methods. The degrees of visualization of the upper, middle, and lower segments of the thoracic duct in the NMRTD group were significantly greater than those in the DLG group (P values were 0.02, 0.00 and 0.00, respectively). All 18 patients (100%) showed dilatation of the lymph vessels in the pelvic cavity and retroperitoneum on abdominopelvic MR and DLG as well as pelvic perineal reflux or leakage on DLG. MR revealed multiple-site abnormalities that could not be detected by DLG, including multiple long T1 and long T2 lesions of the spleen in 8 patients (44.4%), of the subcutaneous in 7 patients (38.9%), of the bone in 6 patients (33.3%), perineal lymphedema in 18 patients (100%), and abdominopelvic effusion in 10 patients (55.6%).

CONCLUSION

NMRTD combined with abdominopelvic MR has advantages in comprehensively evaluating the thoracic duct and multiple systemic abnormalities in patients with chylous leakage of the female reproductive system.

Magnetic resonance imaging of fetal vascular malformations

Vascular anomalies develop during fetal life and can be detected on prenatal ultrasonography and fetal magnetic resonance imaging. Diagnosis of lymphatic, venous, and arteriovenous malformations, as well as congenital hemangiomas and other congenital vascular tumors, may be challenging. The benign vascular anomalies may be difficult to differentiate from malignancies with a similar appearance. In this manuscript, we present a succinct overview of the congenital vascular anomalies that may present in fetal or neonatal life.

Clinical features and current management experience in Gorham-Stout disease: a systematic review

BACKGROUND

Gorham-Stout disease (GSD) is a rare complex lymphatic malformation. Since its initial description in 1838, only approximately 400 patients have been documented. There is currently no consensus on the diagnostic criteria or treatment options for GSD. The objective of this study was to review the clinical characteristics of patients with GSD and determine the current diagnostic and treatment models.

METHODS

A comprehensive search of the PubMed, Web of Science, Embase, and Cochrane Library databases was conducted to identify all relevant literature on GSD published over the decade from 2013 to 2023. The clinical information extracted from these publications was analyzed.

RESULTS

A total of 206 patients with GSD were included in the study, comprising 119 males, 81 females and 6 patients with unknown sex. The age of onset of patients was widely distributed, ranging from 0 to 77 years old. However, the majority of cases occurred in childhood (50.7%). Fifteen patients (10.3%) exhibited an onset age of less than 1 year. The average time from the onset of symptoms to diagnosis was 3.5 years. The number of patients with osteolysis in the axial bone was greater than that in the appendiceal bone (P < 0.05), and the number of patients with multiple osteolytic lesions was greater than that with single osteolytic lesions (77.2% vs. 22.8%). In general, GSD was more likely to occur in the spine (46.1%), ribs (28.6%), hip (23.3%), femur (18.4%), mandible (15.5%) and humerus (15.0%). Pain was the most common symptom, with 68.4% of patients reporting pain in the lesion area. Surgery (66.9%) and bisphosphonates (56.9%) are still the mainstream treatment methods, with a total of 33 (18.2%) patients receiving sirolimus. Pleural effusion was identified as a risk factor for patient mortality (P < 0.05).

CONCLUSIONS

GSD is most commonly observed in children, with a slight male predisposition. It commonly manifests as multiple osteolysis of the axial bone, with pain being the most common symptom. The presence of pleural effusion indicates a serious condition that requires close monitoring to prevent mortality. Despite the advent of novel therapeutic modalities, the management of GSD remains an area in need of further investigation.

Lyve1-Driven NrasQ61R Causes Edema, Enlarged Lymphatic Vessels, and Hepatic Vascular Defects in Embryonic Mice

BACKGROUND

Kaposiform lymphangiomatosis (KLA) is a complex lymphatic anomaly associated with a somatic activating NRAS p.Q61R (NRASQ61R) mutation. KLA is characterized by malformed lymphatic vessels that can lead to effusions and coagulopathy. The goal of this study was to generate an in vivo mouse model to determine if prenatal expression of the NrasQ61R mutation in lymphatic endothelial cells induces disease characteristics found in KLA patients.

PROCEDURE

A Cre-loxP system was used to conditionally express NrasQ61R in cells expressing lymphatic vessel endothelial hyaluronan receptor 1 (Lyve1), a marker of lymphatic and other types of endothelial cells that starts being expressed at embryonic day (E) 7.5. Because pups did not survive birth, embryos were collected at E14.5, E15.5, and E18.5 for gross analysis, histology and immunostaining, and organ whole-mounts.

RESULTS

Staining for NRASQ61R demonstrated robust recombination in the NrasQ61R mutant embryos and localization of NrasQ61R at sites of vascular abnormalities. NrasQ61R mutant embryos had significant edema and dysmorphic jugular lymph sacs with abnormal Lyve1-positive cellular masses. The lymphatic vessel network in the back skin of the NrasQ61R mutant embryos had fewer branch points and increased vessel diameter. NrasQ61R mutant embryos had severe hepatic defects characterized by disordered and enlarged vessels. By E18.5, NrasQ61R mutant embryos were dead.

CONCLUSIONS

Conditional expression of NrasQ61R in Lyve1-positive cells caused edema, abnormal lymphatic development, and hepatic vascular defects in mouse embryos. These findings further support the role of NRASQ61R as a driver of the lymphatic overgrowth, vessel enlargement, and dysfunction in the pathophysiology of KLA.

A single-cell atlas of normal and KRASG12D-malformed lymphatic vessels

Somatic activating mutations in KRAS can cause complex lymphatic anomalies (CLAs). However, the specific processes that drive KRAS-mediated CLAs have yet to be fully elucidated. Here, we used single-cell RNA sequencing to construct an atlas of normal and KrasG12D-malformed lymphatic vessels. We identified 6 subtypes of lymphatic endothelial cells (LECs) in the lungs of adult wild-type mice (Ptx3, capillary, collecting, valve, mixed, and proliferating). To determine when the LEC subtypes were specified during development, we integrated our data with data from 4 stages of development. We found that proliferating and Ptx3 LECs were prevalent during early lymphatic development and that collecting and valve LECs emerged later in development. Additionally, we discovered that the proportion of Ptx3 LECs decreased as the lymphatic network matured but remained high in KrasG12D mice. We also observed that the proportion of collecting and valve LECs was lower in KrasG12D mice than in wild-type mice. Last, we found that immature lymphatic vessels in young mice were more sensitive to the pathologic effects of KrasG12D than mature lymphatic vessels in older mice. Together, our results expand the current model for the development of the lymphatic system and suggest that KRAS mutations impair the maturation of lymphatic vessels.

Complex lymphatic anomalies

Complex lymphatic anomalies are unique diseases marked by abnormal lymphatic vessel development and growth. Imaging is crucial in the evaluation and management of complex lymphatic anomalies, with dynamic contrast-enhanced MR lymphangiography emerging as a valuable modality for visualizing abnormal lymphatic structures and informing treatment decisions. This article gives an overview of complex lymphatic anomalies and their management strategies, focusing specifically on generalized lymphatic anomaly, Gorham-Stout disease, Kaposiform lymphangiomatosis, and central conducting lymphatic anomalies. Simple lymphatic diseases are beyond the scope of this review.

Generalized lymphatic anomaly in a pediatric patient manifesting as a rare presentation of hemorrhagic pleural effusion: a case report

BACKGROUND

Generalized lymphatic anomaly (GLA) is a rare congenital lymphatic malformation (LM) characterized by multiple infiltrating lymphangiomas in various tissues. Owing to its rarity, information on this disease is obtained mainly through case reports, leading to delayed diagnosis. In this study, we reported a case of generalized lymphatic anomaly in a pediatric patient manifesting as hemorrhagic pleural effusion.

CASE PRESENTATION

A 6-year-old female presented with abdominal pain, shortness of breath, chronic cough with yellow sputum production, and diminished respiration accompanied by pleural effusion. Imaging revealed significant left-sided pleural effusion with mediastinal involvement, left lung atelectasis, and multiple cystic lesions in both liver and spleen. Thoracoscopic exploration was conducted in response to her active intrathoracic bleeding, which identified a persistently hemorrhagic mass in the left mediastinum. The mass in the left mediastinum was removed, and pathological examination confirmed hyperplasia and expansion of the papillary endothelial cells within the lymphatic vessels. After intensive anti-infection therapy and symptomatic and supportive treatment, the patient's condition improved significantly. The regular outpatient follow-ups were continued until July 2024. Subsequent positron emission tomography (PET)CT at another hospital revealed multiple skeletal lesions in the limbs. Following treatment with sirolimus, no recurrence of pleural effusion was observed, and the patient's condition remained stable.

CONCLUSION

In patients with generalized lymphatic anomalies (GLAs), involvement of the thoracic cavity may lead to hemorrhagic pleural effusion, thereby broadening the landscape of GLA phenotypic presentations. Furthermore, this case highlights the importance of complete radiological evaluation of susceptible patients with GLA to avoid diagnostic delay in this morbid condition. We also review recently discovered genetic changes underlying lymphatic anomaly development and the progress of treatment.

Clinical characteristics and risk factors for acute abdomen in patients with abdominal lymphatic malformations

OBJECTIVE

The diagnosis of abdominal lymphatic malformations (ALMs) is often overlooked in clinical practice. However, reports in the literature about ALMs are limited to case reports and series with small sample sizes. This study aimed to review our currently available data to describe the clinical characteristics of ALMs and evaluate the risk factors for acute abdomen caused by ALMs.

METHODS

We reviewed the records of patients with ALMs who were diagnosed between December 2008 and January 2023 in our institution. The associations between acute abdomen and ALMs were analyzed based on single-factor and multivariate logistic regression analyses.

RESULTS

This study included 345 patients with pathologically confirmed ALMs, with a slight female predominance of 1:1.4. Approximately 39.1% (135/345) of patients were asymptomatic, and 24.6% (85/345) presented with acute abdomen. Among the ALMs in the cohort, 42.6% (147/345) were retroperitoneal lymphatic malformations (LMs). The maximal lesion dimensions in patients with acute abdomen and nonacute abdomen were 10.0 cm and 7.8 cm, respectively, with no significant difference based on multivariate analyses. Children were more likely to develop acute abdomen than adults were (P = .002; odds ratio, 5.128; 95% confidence interval, 1.835-14.326). ALMs accompanying acute abdomen were more common for lesions involving the small intestinal mesentery (P = .023; odds ratio, 2.926; 95% confidence interval, 1.157-7.400).

CONCLUSIONS

ALMs are rare with an insidious onset, and retroperitoneal LMs are the most common ALMs, followed by jejunal mesenteric LMs. Our retrospective analysis suggested that young age and small intestinal mesenteric lymphatic malformation are independent risk factors for acute abdomen with ALMs.

Kaposiform Lymphangiomatosis as a Cause of Vaginal Bleeding & Discharge: A Case Report

BACKGROUND

Prepubertal vaginal bleeding is a common presentation for pediatric adolescent gynecologists with a broad differential diagnosis that historically may not have included complex lymphatic anomalies. However, given recent consensus criteria and imaging capabilities, this may be a condition that pediatric adolescent gynecologists see more frequently in the future.

CASE

We present a case of a 5-year-old pre-pubertal girl whose only presenting symptoms of a rare complex lymphatic anomaly was copious vaginal bleeding. After three vaginoscopies, two hysteroscopies, two pelvic MRIs, and a percutaneous ultrasound guided core needle biopsy, this patient was eventually diagnosed with Kaposiform lymphangiomatosis at age 9 years-old, and she is now being treated medically with sirolimus, a mammalian target of rapamycin (mTOR) inhibitor, with improvement in her symptoms.

SUMMARY AND CONCLUSION

Complex lymphatic anomalies should be considered after initial and secondary workups for pre-pubertal vaginal bleeding or copious vaginal discharge are negative. Furthermore, this case illustrates the value of pelvic MRI in the setting of unknown cause of vaginal bleeding when typical workup is negative.

Clinical approach for pulmonary lymphatic disorders

In this editorial, we discuss the clinical implications of the article "Lymphatic plastic bronchitis and primary chylothorax: A study based on computed tomography lymphangiography" published by Li et al. Pulmonary lymphatic disorders involve abnormalities in the lymphatic tissues within the thoracic cavity. Specifically, pulmonary lymphatic perfusion syndrome describes a condition where the flow of lymphatic fluid in the lungs is redirected towards abnormally widened lymphatic vessels. Clinically, individuals with this syndrome may experience symptoms such as chyloptysis, plastic bronchitis (PB), chylothorax, chylopericardium, and interstitial lung disease. These disorders can be caused by various factors, including PB, chylothorax, and complex lymphatic malformations. Advancements in lymphatic imaging techniques, such as intranodal lymphangiography, computed tomography lymphangiography, and dynamic contrast-enhanced magnetic resonance lymphangiography, have enabled the detection of abnormal lymphatic flow. This has enhanced our understanding of the pathophysiology of these conditions. Additionally, innovative minimally invasive treatments, such as thoracic duct embolization, selective embolization of lymphatic channels, and surgical procedures aim to improve clinical condition of patients and address their dietary needs.

Case Report: MDFIC gene mutation resulting in central conducting lymphatic anomaly facilitates group A Streptococcus sepsis

Background

Central conducting lymphatic anomaly (CCLA) is a heterogeneous disorder characterized by structural anomalies in the main collecting lymphatic vasculature. These anomalies result in chronic chylous leaks, causing issues such as congenital hydrothorax and potentially impairing the normal immune response. Recently, mutations in the MyoD family inhibitor domain-containing (MDFIC) gene have been identified as a cause of CCLA. Group A Streptococcus infections are common, and timely identification of patients at risk for severe complications is crucial.

Case presentation

Here, we present the case of a 13-year-old female patient with CCLA associated with an MDFIC mutation, who suffered from a severe group A Streptococcus sepsis. Initially, the patient was unresponsive to aggressive fluid resuscitation. Although the course of the sepsis was severe, standardized treatment according to the surviving sepsis campaign proved effective in stabilizing the patient.

Discussion

The patient's MDFIC mutation may have contributed to the severe clinical course of the sepsis. It is theorized that this mutation affects the function of the immune system both indirectly, by causing CCLA, and directly, by potentially influencing transcriptional activity in immune cells. More research on the effect of MDFIC mutations on immune responses is required.

Complex lymphatic anomalies: Challenging diagnostic considerations

Diagnosis of complex lymphatic anomalies can be difficult, and biopsies can be associated with significant morbidity. Mediastinal masses with features such as osseous involvement warrant thorough noninvasive evaluation prior to biopsy.

Mental and physical health of adult patients affected by complex vascular anomalies

OBJECTIVE

We examined care and communication factors that affect physical and mental health for patients with complex vascular anomalies (VAs).

METHODS

VA patients (N = 135) completed an online survey with measures of ability to navigate healthcare, quality of information exchange, perceived stigma, and demographic variables. We performed linear regression to determine if these variables were associated with mental and physical health.

RESULTS

Physical and mental health were associated with information exchange (β = .41, 95% CI=.12 -.69; β = .33, 95% CI=.04 -.62), stigma (β = -.49, 95% CI=-.74 to -.24; β = -.63, 95% CI=-.89 to -.38), and education (β = 4.00, 95% CI=.63 - 7.38; β = 3.44, 95% CI=.06 to 6.82). Ability to navigate healthcare was associated with health outcomes in our bivariate model, but not significant in a multivariate model.

CONCLUSION

The results underscore the importance of effective information exchange. Poor information exchange was associated with worse physical and mental health. VA patients with lower education levels and higher perceived stigma reported poorer health outcomes and likely face many struggles accessing care.

PRACTICE IMPLICATIONS

Patient-centered information exchange between clinicians and patients is needed to address unmet information needs. Clinicians can also reduce perceived stigma by validating patients, and should provide resources to reduce disparities related to education.

Indication for a Pneumocystis Prophylaxis Therapy in Patients with Vascular Anomalies Treated with PIK3/AKT/mTOR Pathway Inhibitors: Experts' Opinion and Systematic Review from the Literature

BACKGROUND

Vascular anomalies (VAs) are increasingly being treated with PI3K/AKT/mTOR pathway inhibitors. These drugs have immunosuppressive properties and thus theoretically overexpose patients to opportunistic infections, especially Pneumocystis jirovecii pneumonia (PJP). PJP prophylaxis use lacks consensus. We aimed to investigate the prevalence of PJP in patients receiving mTOR/PI3K/AKT inhibitors for VAs and determine any indication for pneumocystis prophylaxis in this population.

METHODS

The study was conducted in 2 parts: (1) we sent a survey to a panel of international experts of VAs asking about their use of pneumocystis prophylaxis drugs and (2) we performed a systematic review of the literature of all published cases of patients receiving these drugs for VA to estimate the prevalence of PJP in this population.

RESULTS

Answers from 68 experts were analyzed: 21 (30.9%) answered they always add PJP prophylaxis when prescribing mTOR inhibitors, 20 (29.4%) case-by-case, and 27 (39.7%) never. For the systematic review, among 3,053 reports screened, 217 were included involving 1,189 patients (1,143 received sirolimus, 38 everolimus, 4 alpelisib, 4 miransertib). Among the 1,189 cases, 2 (0.2%) PJP were reported: one under sirolimus and one under everolimus. Thus, the prevalence of PJP was estimated at 0.88 cases/1,000 patients under sirolimus (95% CI: -0.84 to 2.59) and 26.31 cases/1,000 under everolimus (95% CI: -24.58 to 77.18). Patients with PJP never received prophylaxis drugs. We found no PJP cases under alpelisib and miransertib. PJP prophylaxis was given in 218 (18.3%) cases, more frequently for children (91.3 vs. 77.2% in the non-prophylaxis group, p = 0.012), mostly trimethoprim-sulfamethoxazole (186 patients, 85.3%).

CONCLUSION

Our study shows that even if PJP is a rare event, it may occur in patients with VAs treated with an mTOR inhibitor. Although our results cannot allow for revising guidelines, prophylaxis with TMP-SMX might be appropriate for a subgroup of patients with risk factors for PJP.

Vascular Anomalies Care in the United States: A Cross-Sectional National Survey

OBJECTIVE

To characterize the current distribution, composition, and practice patterns of multidisciplinary vascular anomalies (VAs) teams in the US.

STUDY DESIGN

This is a cross-sectional survey of children's hospitals in the US offering VAs care. We approached 142 children's hospitals that provided care for VAs via email. The survey evaluated VA clinic location, medical staffing, research participation, and treatments offered. The survey was administered between October 2021 and July 2022.

RESULTS

Participants from 95 eligible hospitals responded to the survey (response rate = 67%). Large areas of the Midwest and Northwest US had no available multidisciplinary VA teams or clinics. Most respondents worked at academic centers (89%), with 66% at a freestanding children's hospital, and 56% reported having a multidisciplinary clinic. Most common physician participants in clinic included hematology-oncology (91%), interventional radiology (87%), dermatology (85%), plastic surgery (81%), and otolaryngology (74%). Only 38% of programs included medical geneticists. Smaller hospitals had fewer medical and ancillary staff and offered fewer therapeutic options. Research was available at most larger institutions (69%) but less commonly at smaller hospitals (34%).

CONCLUSIONS

Major portions of the US lack multidisciplinary VA care. Furthermore, VA programs vary in composition and geneticists are absent from the majority of programs. These findings should inform efforts to address disparate access and develop standards of care for multidisciplinary VA care in the US.

Hyperactive KRAS/MAPK signaling disrupts normal lymphatic vessel architecture and function

Complex lymphatic anomalies (CLAs) are sporadically occurring diseases caused by the maldevelopment of lymphatic vessels. We and others recently reported that somatic activating mutations in KRAS can cause CLAs. However, the mechanisms by which activating KRAS mutations cause CLAs are poorly understood. Here, we show that KRASG12D expression in lymphatic endothelial cells (LECs) during embryonic development impairs the formation of lymphovenous valves and causes the enlargement of lymphatic vessels. We demonstrate that KRASG12D expression in primary human LECs induces cell spindling, proliferation, and migration. It also increases AKT and ERK1/2 phosphorylation and decreases the expression of genes that regulate the maturation of lymphatic vessels. We show that MEK1/2 inhibition with the FDA-approved drug trametinib suppresses KRASG12D-induced morphological changes, proliferation, and migration. Trametinib also decreases ERK1/2 phosphorylation and increases the expression of genes that regulate the maturation of lymphatic vessels. We also show that trametinib and Cre-mediated expression of a dominant-negative form of MEK1 (Map2k1 K97M) suppresses KRASG12D-induced lymphatic vessel hyperplasia in embryos. Last, we demonstrate that conditional knockout of wild-type Kras in LECs does not affect the formation or function of lymphatic vessels. Together, our data indicate that KRAS/MAPK signaling must be tightly regulated during embryonic development for the proper development of lymphatic vessels and further support the testing of MEK1/2 inhibitors for treating CLAs.

Generalized lymphatic anomaly in adult patients: An eminently radiological diagnosis

Generalized lymphatic anomaly (GLA) is an uncommon congenital disease secondary to the proliferation of lymphatic vessels in any organ except the central nervous system. GLA has a wide spectrum of clinical and radiological presentations, among which osteolytic lesions are the most widespread, being the ribs the most commonly affected bone. GLA is diagnosed mainly in children and young adults; nevertheless, on rare occasions it can remain asymptomatic and be detected incidentally in older patients. We present an unusual case of GLA in an asymptomatic 54-year-old man who had atypically distributed, purely cystic bone lesions on CT; measuring the Hounsfield (HU) of these lesions enabled us to suspect GLA. This suspicion was confirmed with MRI, PET/CT, CT-guided fine-needle aspiration biopsy, and fluoroscopy-guided percutaneous vertebral biopsy. After surgical resection of one of the lesions, histologic study provided the definitive diagnosis.

Designs used in published therapeutic studies of rare superficial vascular anomalies: a systematic literature search

BACKGROUND

Rare superficial vascular anomalies represent a wide range of diseases. Their management is difficult given the broad spectrum and the lack of clinical trials assessing treatment efficacy. A randomized clinical trial of vascular anomalies is difficult because of the rarity of the diseases and is enhanced by the population of interest often being children. Therefore, suitable designs are needed. We conducted a methodological systematic literature search to identify designs implemented for investigating the treatment of rare superficial vascular anomalies.

METHODS

We conducted a literature search on January 25, 2021, of the PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), Embase, ClinicalTrials.gov and European Union Clinical Trials Register databases. This systematic methodological literature search was registered at the Prospective Register of Systematic Reviews (PROSPERO: CRD42021232449). Randomized and non-randomized studies were included if they met the following criteria: were prospective studies of rare superficial vascular anomaly therapies, dealt with humans (adults and children) and were published in English from 2000. We excluded case reports/case series reporting fewer than 10 patients, reviews, retrospective studies, animal studies, studies of systemic or common vascular anomalies and non-therapeutic studies. We did not assess risk of bias in the included studies because our review was a methodological one focused on the design used. The review provided a descriptive analysis of relevant features of eligible research studies.

RESULTS

From 2046 articles identified, we included 97 studies (62 reports and 35 ongoing studies): 25 randomized controlled studies, 7 non-randomized comparative studies, 64 prospective cohorts and 1 case series. Among the 32 comparative studies included, 21 used a parallel-group design. The 11 other studies used different designs such as cross-over, randomized placebo phase, delayed-start, within-person, or challenge-dechallenge-rechallenge or used a historical control group or an observational run-in period.

CONCLUSIONS

Our systematic literature search highlights the lack of randomized control trials in superficial vascular anomalies due to the rarity of patients and their heterogeneity. New designs are emerging and can overcome the limitations of testing treatments in parallel groups.

Back to the Future II-A Comprehensive Update on the Rapidly Evolving Field of Lymphatic Imaging and Interventions

ABSTRACT

Lymphatic imaging and interventional therapies of disorders affecting the lymphatic vascular system have evolved rapidly in recent years. Although x-ray lymphangiography had been all but replaced by the advent of cross-sectional imaging and the scientific focus shifted to lymph node imaging (eg, for detection of metastatic disease), interest in lymph vessel imaging was rekindled by the introduction of lymphatic interventional treatments in the late 1990s. Although x-ray lymphangiography is still the mainstay imaging technique to guide interventional procedures, several other, often less invasive, techniques have been developed more recently to evaluate the lymphatic vascular system and associated pathologies. Especially the introduction of magnetic resonance, and even more recently computed tomography, lymphangiography with water-soluble iodinated contrast agent has furthered our understanding of complex pathophysiological backgrounds of lymphatic diseases. This has led to an improvement of treatment approaches, especially of nontraumatic disorders caused by lymphatic flow abnormalities including plastic bronchitis, protein-losing enteropathy, and nontraumatic chylolymphatic leakages. The therapeutic armamentarium has also constantly grown and diversified in recent years with the introduction of more complex catheter-based and interstitial embolization techniques, lymph vessel stenting, lymphovenous anastomoses, as well as (targeted) medical treatment options. The aim of this article is to review the relevant spectrum of lymphatic disorders with currently available radiological imaging and interventional techniques, as well as the application of these methods in specific, individual clinical situations.

Investigation into the genetics of fetal congenital lymphatic anomalies

OBJECTIVE

Congenital lymphatic anomalies (LAs) arise due to defects in lymphatic development and often present in utero as pleural effusion, chylothorax, nuchal and soft tissue edema, ascites, or hydrops. Many LAs are caused by single nucleotide variants, which are not detected on routine prenatal testing.

METHODS

Demographic data were compared between two subcohorts, those with clinically significant fetal edema (CSFE) and isolated fetal edema. A targeted variant analysis of LA genes was performed using American College of Medical Genetics criteria on whole exome sequencing (WES) data generated for 71 fetal edema cases who remained undiagnosed after standard workup.

RESULTS

CSFE cases had poor outcomes, including preterm delivery, demise, and maternal preeclampsia. Pathogenic and likely pathogenic variants were identified in 7% (5/71) of cases, including variants in RASopathy genes, RASA1, SOS1, PTPN11, and a novel PIEZO1 variant. Variants of uncertain significance (VOUS) were identified in 45% (32/71) of cases. In CSFEs, VOUS were found in CELSR1, EPHB4, TIE1, PIEZO1, ITGA9, RASopathy genes, SOS1, SOS2, and RAF1.

CONCLUSIONS

WES identified pathogenic and likely pathogenic variants and VOUS in LA genes in 51% of fetal edema cases, supporting WES and expanded hydrops panels in cases of idiopathic fetal hydrops and fluid collections.

Oral antibiotic prophylaxis for infection in patients with vascular anomalies receiving sirolimus treatment: a multicenter retrospective study

OBJECTIVES

Patients with vascular anomalies (VAs) who receive oral sirolimus may be at high risk of infectious complications. Antibiotic prophylaxis with trimethoprim-sulfamethoxazole (TMP-SMZ) has been advocated. However, there have been few evidence-based analyses on this topic. This study assessed the effect of prophylactic TMP-SMZ on the incidence of infections in VA patients receiving sirolimus monotherapy.

METHODS

A retrospective, multicenter chart review was performed on all VA patients receiving sirolimus treatment from August, 2013 to January, 2021.

RESULTS

Before January 2017, 112 patients were treated with sirolimus without antibiotic prophylaxis. In the subsequent period, 195 patients were treated with TMP-SMZ for at least 12 months during sirolimus therapy. The percentage of patients with at least one serious infection during the initial 12 months of sirolimus treatment did not differ between the groups (difference, 1.1%; 95% CI - 7.0-8.0%). We observed no difference in the incidence of individual infection or total adverse events between the groups. The rate of sirolimus discontinuation due to adverse events did not differ significantly between groups.

CONCLUSIONS

We demonstrated that prophylactic TMP-SMZ does not decrease the incidence of infection or improve tolerance in VA patients receiving sirolimus monotherapy.

Kaposiform lymphangiomatosis: Diagnosis, pathogenesis, and treatment

Kaposiform lymphangiomatosis (KLA) is a life-threatening rare disease that can cause substantial morbidity, mortality, and social burdens for patients and their families. Diagnosis often occurs long after initial symptoms, and there are few centers in the world with the expertise to diagnose and care for patients with the disease. KLA is a lymphatic anomaly and significant advancements have been made in understanding its pathogenesis and etiology since its first description in 2014. This review provides multidisciplinary, comprehensive, and state-of-the-art information on KLA patient presentation, diagnostic imaging, pathology, organ involvement, genetics, and pathogenesis. Finally, we describe current therapeutic approaches, important areas for research, and challenges faced by patients and their families. Further insights into the pathogenesis of KLA may advance our understanding of other vascular anomalies given that similar signaling pathways may be involved.

The lymphatic vasculature in lung function and respiratory disease

The lymphatic vasculature maintains tissue homeostasis via fluid drainage in the form of lymph and immune surveillance due to migration of leukocytes through the lymphatics to the draining lymph nodes. Lymphatic endothelial cells (LECs) form the lymphatic vessels and lymph node sinuses and are key players in shaping immune responses and tolerance. In the healthy lung, the vast majority of lymphatic vessels are found along the bronchovascular structures, in the interlobular septa, and in the subpleural space. Previous studies in both mice and humans have shown that the lymphatics are necessary for lung function from the neonatal period through adulthood. Furthermore, changes in the lymphatic vasculature are observed in nearly all respiratory diseases in which they have been analyzed. Recent work has pointed to a causative role for lymphatic dysfunction in the initiation and progression of lung disease, indicating that these vessels may be active players in pathologic processes in the lung. However, the mechanisms by which defects in lung lymphatic function are pathogenic are understudied, leaving many unanswered questions. A more comprehensive understanding of the mechanistic role of morphological, functional, and molecular changes in the lung lymphatic endothelium in respiratory diseases is a promising area of research that is likely to lead to novel therapeutic targets. In this review, we will discuss our current knowledge of the structure and function of the lung lymphatics and the role of these vessels in lung homeostasis and respiratory disease.

Complex Lymphatic Anomalies: Report on a Patient Registry Using the Latest Diagnostic Guidelines

Objective: Generalized lymphatic anomaly (GLA), Gorham-Stout disease (GSD), kaposiform lymphangiomatosis (KLA), and central conducting lymphatic anomaly (CCLA) are rare, multisystem lymphatic disorders, referred to as complex lymphatic anomalies (CLAs). Their etiology remains poorly understood; however, somatic activating mutations have recently been discovered, and the results of targeted treatments are promising. This study aimed to elaborate on the phenotypic description of CLA. Methods: Thirty-six consecutive patients were recruited for the "GLA/GSD Registry" of the University Hospital of Freiburg, Germany (2015-2021). Clinical data were prospectively collected provided that a signed informed consent form was obtained. The latest proposed diagnostic guidelines were retrospectively applied. Results: Thirty-two patients (38% males) were included in the study; 15 GLA, 10 GSD, 3 KLA, and 4 CCLA patients were identified. Eighty-four percent already had symptoms by the age of 15 years. Osteolysis and periosseous soft-tissue infiltration were associated with GSD (p < 0.001 and p = 0.011, respectively), ascites and protein-losing enteropathy with CCLA (p = 0.007 and p = 0.004, respectively), and consumption coagulopathy with KLA (p = 0.006). No statistically significant differences were found in organ involvement, distribution of osteolytic lesions, number of affected bones and fractures. Twenty-five patients had complications; one patient with GLA died despite multimodal treatment. Spontaneous regression was seen in one patient with untreated KLA. Conclusions: CLA are rare, and their overlapping clinical presentations make differential diagnosis difficult. The characterization of our case series contributes to the phenotypic description and differentiation of these four clinical entities. A further understanding of their pathogenesis is crucial for evaluating targeted therapies and optimizing medical care.

French national diagnosis and care protocol (PNDS, protocole national de diagnostic et de soins): cystic lymphatic malformations

Cystic lymphatic malformations (LMs) are rare chronic conditions which management differs according to the type (macrocystic LMs, microcystic LMs or both). Studies are lacking due to rarity of the pathology. We aimed to establish a French National Diagnosis and Care Protocol (PNDS: Protocole National de Diagnostic et de Soins), to provide health professionals with free open access synthesis on optimal management and care of patients with LMs ( https://www.has-sante.fr/upload/docs/application/pdf/2021-03/malformations_lymphatiques_kystiques_-_pnds.pdf ). The process included a critical review of the literature and multidisciplinary expert consensus. LMs are congenital but are not always discovered at birth. Nearly 75% of them are located in the head and neck because of the highly dense lymphatic system in this region. Physical examination (showing painless masses with normal skin color and depressible consistency, or cutaneous/mucosal lymphangiectasia) and color Doppler ultrasonography, usually allow for diagnosis. MRI (involving T2 sequences with fat saturation in at least two spatial planes) is the tool of choice for evaluating anatomical extension, characterizing lesions (microcystic and macrocystic), and before considering therapeutic management. A biopsy, coupled to a blood sample, can also be used for molecular biology analyses, to search for activating mutations of the PIK3CA gene, particularly with LM integrating in a syndromic form (CLOVES or Klippel-Trenaunay syndrome) but also in certain isolated (or common) LMs. The spontaneous evolution of LMs, in particular microcystic forms, is often toward progressive aggravation, with an increase in the number of vesicles, thickening, increased oozing and bleeding, while pure macrocystic LMs may regress due to "natural sclerosis", i.e. fibrosis secondary to an inflammatory reorganization after common infantile infections. In case of voluminous LMs or syndromic forms, functional and psychological repercussions can be major, deteriorating the patient's quality of life. LMs must be treated by physicians integrated in multidisciplinary teams, and be personalized. Management is a life-long process that involves one or several of these therapies: conservative management, physical therapy (compression), sclerotherapy, surgery, drugs such as mTOR inhibitors (sirolimus), that has shown efficacy in decreasing the volume of LMs, and, more recently, PI3K-inhibitors in syndromic forms. Psychological and social support is necessary, taking into account the patient and his family.

Difficult Therapeutic Decisions in Gorham-Stout Disease-Case Report and Review of the Literature

Gorham-Stout disease (GSD) is a very rare, life-threatening condition characterized by the proliferation of lymphatic vessels and osteolysis. Unfortunately, no standard treatment has been determined for management of GSD. The available therapies are not equally effective and carry substantial side-effects. We report a 42-year-old female with GSD manifested in multifocal osteolysis and chronic chylothorax and ascites. The combined treatment with sirolimus and zoledronic acid due to its synergism of action was introduced. To our knowledge, this is the first Polish case report of adult patients with Gorham-Stout disease.

Multicompartment Dynamic Contrast Magnetic Resonance Lymphangiography in Diagnosis of Complicated Lymphatic Anomaly

Background: To describe the dynamic contrast magnetic resonance lymphangiography (DCMRL) findings of three patients with complicated lymphatic anomaly (CLA) and protein losing enteropathy. We further discuss the importance of a multicompartment (intrahepatic [IH], intramesenteric [IM], and intranodal [IN]) DCMRL in delineating central lymphatic flow pathologies. Methods and Results: This is a retrospective study of three patients-one adult and two children who individually underwent the three-compartment DCMRL, namely IN-DCMRL, IH-DCMRL, and IM-DCMCRL. Findings from the results of the DCMRL for these three patients were obtained from the medical records and compared. Using the multicompartment imaging modalities, chylous fluid leakage into the peritoneum was observed using IM-DCMRL and IH-DCMRL but not IN-DCMRL for one of the patients in the case series. In contrast, leakage of chyle into the mediastinum was noted using IN-DCMRL but not IH-DCMRL and IM-DCMRL on another patient in this case series. Conclusion: Owing to the variability in outlining lymphatic flow pathologies, multicompartment imaging gives a more global picture of individual conduction disorders, has the potential to improve clinical assessment, and in some cases leads to a diagnosis of the abnormality and thus provides a better understanding of lymphatic flow anomalies in patients with CLAs.

How we approach the diagnosis and management of complex lymphatic anomalies

Complex lymphatic anomalies (CLA) are congenital diseases of the lymphatic circulation system that are associated with significant morbidity and early mortality. While guidelines for the comprehensive evaluation of the CLA were recently published, the diagnostic approach and medical management are not standardized. This article presents the clinical features of four CLA: Gorham-Stout disease, generalized lymphatic anomaly, kaposiform lymphangiomatosis, and central collecting lymphatic anomaly. We also offer three cases from the authors' practice and our views on diagnostic testing and disease management including supportive care, medical therapies, and other interventions.

How we approach pediatric congenital chylous effusions and ascites

Congenital lymphatic leak may develop in patients with maldeveloped lymphatics and result in life-threatening fluid and electrolyte imbalance, protein deficiency, and immunodeficiency. Rapid diagnosis and therapy are necessary to prevent these complications; however, the field lacks clinical trials to support standardized diagnostic treatment guidelines. We present our current multidisciplinary approach to the diagnosis and management of congenital lymphatic leak including chylous pleural effusions and ascites. Depending on the rate of lymphatic leak, therapy can range from observation with nutritional modifications to surgical and interventional procedures aimed to reduce lymphatic drainage. Modalities to image central and peripheral lymphatics have advanced considerably. Genetic variants and subsequent targets that drive lymphatic maldevelopment have expanded the repertoire of possible pharmacotherapeutic options.

Osteopathy in Complex Lymphatic Anomalies

Complex Lymphatic Anomalies (CLA) are lymphatic malformations with idiopathic bone and soft tissue involvement. The extent of the abnormal lymphatic presentation and boney invasion varies between subtypes of CLA. The etiology of these diseases has proven to be extremely elusive due to their rarity and irregular progression. In this review, we compiled literature on each of the four primary CLA subtypes and discuss their clinical presentation, lymphatic invasion, osseous profile, and regulatory pathways associated with abnormal bone loss caused by the lymphatic invasion. We highlight key proliferation and differentiation pathways shared between lymphatics and bone and how these systems may interact with each other to stimulate lymphangiogenesis and cause bone loss.

Kaposiform Lymphangiomatosis: Pathologic Aspects in 43 Patients

Kaposiform lymphangiomatosis is an uncommon generalized lymphatic anomaly with distinctive clinical, radiologic, histopathologic, and molecular findings. Herein, we document the pathology in 43 patients evaluated by the Boston Children's Hospital Vascular Anomalies Center from 1999 to 2020. The most frequent presentations were respiratory difficulty, hemostatic abnormalities, and a soft tissue mass. Imaging commonly revealed involvement of some combination of mediastinal, pulmonary, pleural, and pericardial compartments and most often included spleen and skeleton. Histopathology was characterized by dilated, redundant, and abnormally configured lymphatic channels typically accompanied by dispersed clusters of variably canalized, and often hemosiderotic, spindled lymphatic endothelial cells that were immunopositive for D2-40, PROX1, and CD31. An activating lesional NRAS variant was documented in 9 of 10 patients. The clinical course was typically aggressive, marked by hemorrhage, thrombocytopenia, diminished fibrinogen levels, and a mortality rate of 21%.

Lymphatic Anomalies in Children: Update on Imaging Diagnosis, Genetics, and Treatment

Lymphatic anomalies comprise a spectrum of disorders ranging from common localized microcystic and macrocystic lymphatic malformations (LMs) to rare complex lymphatic anomalies, including generalized lymphatic anomaly, Kaposiform lymph-angiomatosis, central conducting lymphatic anomaly, and Gorham-Stout disease. Imaging diagnosis of cystic LMs is generally straightforward, but complex lymphatic anomalies, particularly those with multiorgan involvement or diffuse disease, may be more challenging to diagnose. Complex lymphatic anomalies are rare but associated with high morbidity. Imaging plays an important role in their diagnosis, and radiologists may be the first clinicians to suggest the diagnosis. Furthermore, radiologists are regularly involved in management given the frequent need for image-guided interventions. For these reasons, it is crucial for radiologists to be familiar with the spectrum of entities comprising complex lymphatic anomalies and their typical imaging findings. In this article, we review the imaging findings of lymphatic anomalies, including LMs and complex lymphatic anomalies. We discuss characteristic imaging findings, multimodality imaging techniques used for evaluation, pearls and pitfalls in diagnosis, and potential complications. We also review recently discovered genetic changes underlying lymphatic anomaly development and the advent of new molecularly targeted therapies.

Pathologic Fracture as Presentation of Generalized Lymphangiomatosis in an Eight-Year-Old: A Case Report and Literature Review

Pathologic fractures commonly occur secondary to abnormal skeletal physiology in the context of benign or malignant lesions. Rarely, pathologic fractures may occur in the context of a lymphatic abnormality, such as generalized lymphangiomatosis. This rare disorder is characterized by variable presentations in a broad age range of patients. By understanding the effect of widespread lymphatic anomalies on various organ systems, clinicians will be able to make this diagnosis earlier and with more certainty.

Pathogenic variants in MDFIC cause recessive central conducting lymphatic anomaly with lymphedema

Central conducting lymphatic anomaly (CCLA), characterized by the dysfunction of core collecting lymphatic vessels including the thoracic duct and cisterna chyli, and presenting as chylothorax, pleural effusions, chylous ascites, and lymphedema, is a severe disorder often resulting in fetal or perinatal demise. Although pathogenic variants in RAS/mitogen activated protein kinase (MAPK) signaling pathway components have been documented in some patients with CCLA, the genetic etiology of the disorder remains uncharacterized in most cases. Here, we identified biallelic pathogenic variants in MDFIC, encoding the MyoD family inhibitor domain containing protein, in seven individuals with CCLA from six independent families. Clinical manifestations of affected fetuses and children included nonimmune hydrops fetalis (NIHF), pleural and pericardial effusions, and lymphedema. Generation of a mouse model of human MDFIC truncation variants revealed that homozygous mutant mice died perinatally exhibiting chylothorax. The lymphatic vasculature of homozygous Mdfic mutant mice was profoundly mispatterned and exhibited major defects in lymphatic vessel valve development. Mechanistically, we determined that MDFIC controls collective cell migration, an important early event during the formation of lymphatic vessel valves, by regulating integrin β₁ activation and the interaction between lymphatic endothelial cells and their surrounding extracellular matrix. Our work identifies MDFIC variants underlying human lymphatic disease and reveals a crucial, previously unrecognized role for MDFIC in the lymphatic vasculature. Ultimately, understanding the genetic and mechanistic basis of CCLA will facilitate the development and implementation of new therapeutic approaches to effectively treat this complex disease.

Understanding Lymphatic Anatomy and Abnormalities at Imaging

Lymphatic abnormalities encompass a wide range of disorders spanning solitary common cystic lymphatic malformations (LMs) to entities involving multiple organ systems such as lymphangioleiomyomatosis. Many of these disorders are rare, yet some, such as secondary lymphedema from the treatment of malignancy (radiation therapy and/or lymph node dissection), affect millions of patients worldwide. Owing to complex and variable anatomy, the lymphatics are not as well understood as other organ systems. Further complicating this is the variability in the description of lymphatic disease processes and their nomenclature in the medical literature. In recent years, medical imaging has begun to facilitate a deeper understanding of the physiology and pathologic processes that involve the lymphatic system. Radiology is playing an important and growing role in the diagnosis and treatment of many lymphatic conditions. The authors describe both normal and common variant lymphatic anatomy. Various imaging modalities including nuclear medicine lymphoscintigraphy, conventional lymphangiography, and MR lymphangiography used in the diagnosis and treatment of lymphatic disorders are highlighted. The authors discuss imaging many of the common and uncommon lymphatic disorders, including primary LMs described by the International Society for the Study of Vascular Anomalies 2018 classification system (microcystic, mixed, and macrocystic LMs; primary lymphedema). Secondary central lymphatic disorders are also detailed, including secondary lymphedema and chylous leaks, as well as lymphatic disorders not otherwise easily classified. The authors aim to provide the reader with an overview of the anatomy, pathology, imaging findings, and treatment of a wide variety of lymphatic conditions. ^©RSNA, 2022.

Kaposiform lymphangiomatosis presenting with a Group A Streptococcus pericardial effusion

A 4-year-old child was transferred to the paediatric intensive care unit with acute respiratory failure following 4 days of fever, nausea and vomiting. Chest X-ray on admission had an enlarged cardiac silhouette and transthoracic echo confirmed a large pericardial effusion. An emergent pericardiocentesis was performed at bedside which drained nearly 1000 mL of purulent fluid. Postdrainage course was complicated by acute systolic and diastolic heart failure, thrombocytopenia and acute renal failure. A chest CT and MRI were concerning for a diffuse mediastinal soft-tissue density, so the patient underwent interventional radiology-guided biopsy complicated by haemorrhage requiring mediastinal exploration and subtotal thymectomy. Histopathology revealed changes consistent with kaposiform lymphangiomatosis and MRI demonstrated involvement of the lumbar spine and right hip. Following a course of intravenous antibiotics, the patient was started on sirolimus and prednisolone and ultimately discharged home.

A prospective multicenter study of sirolimus for complicated vascular anomalies

OBJECTIVE

Complicated vascular anomalies (VAs) can be intractable and uncontrollable using conventional treatment and can result in lethal outcomes. We undertook a prospective, multicenter phase II trial to evaluate the efficacy and safety of sirolimus in pediatric patients with complicated VAs.

METHODS

Eligible patients were required to be aged 0 to 14 years and to have a complicated VA. The patients were treated with daily oral sirolimus for 12 months. The primary endpoint was the response, which was measured using sequential volumetric magnetic resonance imaging. The secondary endpoints were the disease severity score and quality of life.

RESULTS

Of 126 patients enrolled on an intention-to-treat basis, 98 (77.8%) had had an objective response to sirolimus, with a ≥20% decrease in lesion volume. Compared with those with arteriovenous malformations, the response rates were higher (>80%) for patients with common lymphatic malformations, venous malformations, kaposiform hemangioendothelioma, and combined malformations with a prominent venous and/or lymphatic component (P < .05). Improvements in the disease severity score and quality of life were obtained in 83.3% and 79.4% of patients, respectively. The most common adverse event was mucositis in 47 patients. More serious adverse events included reversible grade 4 pneumonitis in 3 patients and grade 4 upper respiratory infection in 1 patient. All these adverse events were considered at least possibly related to the treatment.

CONCLUSIONS

Sirolimus is an apparently effective option for pediatric patients with various types of complicated VAs. Close monitoring of possible adverse events is required. The results from the present trial are the basis for future prospective studies using new therapeutic approaches.

Sirolimus (Rapamycin) for Slow-Flow Malformations in Children: The Observational-Phase Randomized Clinical PERFORMUS Trial

Importance

Sirolimus is increasingly being used to treat various vascular anomalies, although evidence of its efficacy is lacking.

Objective

To assess the efficacy and safety of sirolimus for children with slow-flow vascular malformations to better delineate the indications for treatment.

Design, Setting and Participants

This multicenter, open-label, observational-phase randomized clinical trial included 59 children aged 6 to 18 years with a slow-flow vascular malformation who were recruited between September 28, 2015, and March 22, 2018, in 11 French tertiary hospital centers. Statistical analysis was performed on an intent-to-treat basis from December 4, 2019, to November 10, 2020.

Interventions

Patients underwent an observational period, then switched to an interventional period when they received oral sirolimus (target serum levels, 4-12 ng/mL). The switch time was randomized from month 4 to month 8, and the whole study period lasted 12 months for each patient.

Main Outcomes and Measures

The primary outcome was change in the volume of vascular malformations detected on magnetic resonance imaging scan (with centralized interpretation) per unit of time (ie, between the interventional period and the observational period). Secondary outcomes included subjective end points: pain, bleeding, oozing, quality of life, and safety.

Results

Among the participants (35 girls [59.3%]; mean [SD] age, 11.6 [3.8] years), 22 (37.3%) had a pure venous malformation, 18 (30.5%) had a cystic lymphatic malformation, and 19 (32.2%) had a combined malformation, including syndromic forms. Variations in the volume of vascular malformations detected on magnetic resonance imaging scans associated with the duration period were not overall significantly different between the interventional period and the observational period (all vascular malformations: mean [SD] difference, -0.001 [0.007]; venous malformations: mean [SD] difference, 0.001 [0.004]; combined malformations: mean [SD] difference, 0.001 [0.009]). However, a significant decrease in volume was observed for children with pure lymphatic malformations (mean [SD] difference, -0.005 [0.005]). Overall, sirolimus had positive effects on pain, especially for combined malformations, and on bleeding, oozing, self-assessed efficacy, and quality of life. During sirolimus treatment, 56 patients experienced 231 adverse events (5 serious adverse events, none life-threatening). The most frequent adverse event was an oral ulcer (29 patients [49.2%]).

Conclusions and Relevance

This observational-phase randomized clinical trial allows for clarifying the goals of patients and families when starting sirolimus therapy for children older than 6 years. Pure lymphatic malformations seem to be the best indication for sirolimus therapy because evidence of decreasing lymphatic malformation volume per unit of time, oozing, and bleeding and increasing quality of life was found. In combined malformations, sirolimus significantly reduced pain, oozing, and bleeding. Benefits seemed lower for pure venous malformations than for the 2 other subgroups, also based on symptoms.

Trial Registration

ClinicalTrials.gov Identifier: NCT02509468; clinicaltrialsregister.eu Identifier: 2015-001096-43.

Primary lymphoedema

Lymphoedema is the swelling of one or several parts of the body owing to lymph accumulation in the extracellular space. It is often chronic, worsens if untreated, predisposes to infections and causes an important reduction in quality of life. Primary lymphoedema (PLE) is thought to result from abnormal development and/or functioning of the lymphatic system, can present in isolation or as part of a syndrome, and can be present at birth or develop later in life. Mutations in numerous genes involved in the initial formation of lymphatic vessels (including valves) as well as in the growth and expansion of the lymphatic system and associated pathways have been identified in syndromic and non-syndromic forms of PLE. Thus, the current hypothesis is that most cases of PLE have a genetic origin, although a causative mutation is identified in only about one-third of affected individuals. Diagnosis relies on clinical presentation, imaging of the structure and functionality of the lymphatics, and in genetic analyses. Management aims at reducing or preventing swelling by compression therapy (with manual drainage, exercise and compressive garments) and, in carefully selected cases, by various surgical techniques. Individuals with PLE often have a reduced quality of life owing to the psychosocial and lifelong management burden associated with their chronic condition. Improved understanding of the underlying genetic origins of PLE will translate into more accurate diagnosis and prognosis and personalized treatment.

Multidisciplinary Multiagent Treatment of Complex Lymphatic Anomalies with Severe Bone Disease: A Single-Site Experience

Background: Complex lymphatic anomalies (CLA) are a group of conditions that pose diagnostic and therapeutic challenges due to their rarity and overlapping clinical findings. This case series describes the complex pathology and novel combination therapies of three patients diagnosed with various types of CLA. Methods and Results: A retrospective review of medical records was performed for three patients treated for CLA between 2011 and 2019. Diagnostics, imaging, treatment, and follow-up were reviewed in the electronic medical record and combined with the literature review within the analysis. One patient had involvement of her skull base and ear canals, diagnosed after ear canal abnormalities were detected on computed tomography following meningitis. The second patient had involvement of her posterior ribs and T7-T12 vertebral bodies, with thoracic instability requiring a back brace. The third patient had involvement of his left lower extremity and hemipelvis, necessitating a left above the knee amputation. Case 1 progressed on sirolimus and pamidronate but responded to zoledronic acid (ZA). She developed flares of coagulopathy and cellulitis that required reinforcement with vincristine and steroid pulses. Similarly, case 2 progressed on sirolimus and ZA alone, but achieved stable disease with added vincristine. Upon further disease progression, stabilization was obtained by the reinforcement of ZA. Case 3 required a combination of surgery as well as medical management with sirolimus and pamidronate. All three patients now have stable disease. Conclusion: This case series depicts a multidisciplinary and multiagent approach to the management of CLA with severe bony involvement using sirolimus, bisphosphonates, vincristine, and steroids.

A review of mechanisms of disease across PIK3CA-related disorders with vascular manifestations

BACKGROUND

PIK3CA-related disorders include vascular malformations and overgrowth of various tissues that are caused by postzygotic, somatic variants in the gene encoding phosphatidylinositol-3-kinase (PI3K) catalytic subunit alpha. These mutations result in activation of the PI3K/AKT/mTOR signaling pathway. The goals of this review are to provide education on the underlying mechanism of disease for this group of rare conditions and to summarize recent advancements in the understanding of, as well as current and emerging treatment options for PIK3CA-related disorders.

MAIN BODY

PIK3CA-related disorders include PIK3CA-related overgrowth spectrum (PROS), PIK3CA-related vascular malformations, and PIK3CA-related nonvascular lesions. Somatic activating mutations (predominantly in hotspots in the helical and kinase domains of PIK3CA, but also in other domains), lead to hyperactivation of the PI3K signaling pathway, which results in abnormal tissue growth. Diagnosis is complicated by the variability and overlap in phenotypes associated with PIK3CA-related disorders and should be performed by clinicians with the required expertise along with coordinated care from a multidisciplinary team. Although tissue mosaicism presents challenges for confirmation of PIK3CA mutations, next-generation sequencing and tissue selection have improved detection. Clinical improvement, radiological response, and patient-reported outcomes are typically used to assess treatment response in clinical studies of patients with PIK3CA-related disorders, but objective assessment of treatment response is difficult using imaging (due to the heterogeneous nature of these disorders, superimposed upon patient growth and development). Despite their limitations, patient-reported outcome tools may be best suited to gauge patient improvement. New therapeutic options are needed to provide an alternative or supplement to standard approaches such as surgery and sclerotherapy. Currently, there are no systemic agents that have regulatory approval for these disorders, but the mTOR inhibitor sirolimus has been used for several years in clinical trials and off label to address symptoms. There are also other agents under investigation for PIK3CA-related disorders that act as inhibitors to target different components of the PI3K signaling pathway including AKT (miransertib) and PI3K alpha (alpelisib).

CONCLUSION

Management of patients with PIK3CA-related disorders requires a multidisciplinary approach. Further results from ongoing clinical studies of agents targeting the PI3K pathway are highly anticipated.

Lymphatic Malformations: Genetics, Mechanisms and Therapeutic Strategies

Lymphatic vessels maintain tissue fluid homeostasis by returning to blood circulation interstitial fluid that has extravasated from the blood capillaries. They provide a trafficking route for cells of the immune system, thus critically contributing to immune surveillance. Developmental or functional defects in the lymphatic vessels, their obstruction or damage, lead to accumulation of fluid in tissues, resulting in lymphedema. Here we discuss developmental lymphatic anomalies called lymphatic malformations and complex lymphatic anomalies that manifest as localized or multifocal lesions of the lymphatic vasculature, respectively. They are rare diseases that are caused mostly by somatic mutations and can present with variable symptoms based upon the size and location of the lesions composed of fluid-filled cisterns or channels. Substantial progress has been made recently in understanding the molecular basis of their pathogenesis through the identification of their genetic causes, combined with the elucidation of the underlying mechanisms in animal disease models and patient-derived lymphatic endothelial cells. Most of the solitary somatic mutations that cause lymphatic malformations and complex lymphatic anomalies occur in genes that encode components of oncogenic growth factor signal transduction pathways. This has led to successful repurposing of some targeted cancer therapeutics to the treatment of lymphatic malformations and complex lymphatic anomalies. Apart from the mutations that act as lymphatic endothelial cell-autonomous drivers of these anomalies, current evidence points to superimposed paracrine mechanisms that critically contribute to disease pathogenesis and thus provide additional targets for therapeutic intervention. Here, we review these advances and discuss new treatment strategies that are based on the recently identified molecular pathways.

Abnormal pulmonary lymphatic flow in patients with paediatric pulmonary lymphatic disorders: Diagnosis and treatment

Pulmonary lymphatic disorders are characterized by the presence of the abnormal lymphatic tissues in the thoracic cavity, presenting clinically as chylothorax, chylopericardium, chyloptysis, interstitial lung disease and plastic bronchitis. These conditions include: neonatal chylothorax, cardiac and non-cardiac plastic bronchitis, non-traumatic chylothorax, post congenital cardiac surgery chylothorax and complex lymphatic malformations. Recently developed lymphatic imaging techniques, such as intranodal lymphangiography and dynamic contrast enhanced magnetic resonance lymphangiography demonstrated abnormal pulmonary lymphatic flow from thoracic duct into pulmonary parenchyma as a pathophysiological mechanism of these diseases. Novel minimally invasive lymphatic interventions, such as thoracic duct embolization, interstitial lymphatic embolization and surgical lympho-venous anastomosis, provide an effective treatment of these conditions.

Italian inter-society expert panel position on radiological exposure in Neonatal Intensive Care Units

BACKGROUND

In the recent years, clinical progress and better medical assistance for pregnant women, together with the introduction of new complex technologies, has improved the survival of preterm infants. However, this result requires frequent radiological investigations mostly represented by thoracic and abdominal radiographs in incubators. This document was elaborated by an expert panel Italian inter-society working group (Radiologists, Paediatricians, Medical Physicists) with the aim to assist healthcare practitioners in taking choices involving radiation exposures of new-born infants and to provide practical recommendations about justification and optimization in Neonatal Intensive Care Units. The adherence to these practice recommendations could ensure a high quality and patient safety. More complex and less common radiological practice, such as CT scan or fluoroscopy have been excluded.

METHODS

The consensus was reached starting from current good practice evidence shared by four scientific societies panel: AIFM (Italian Association of Physics in Medicine), SIN (Italian Neonatology Society), SIP (Italian Paediatric Society), SIRM (Italian Medical Radiology Society) in order to guarantee good standard practices for every professional involved in Neonatal Intensive Care Units (NICU). The report is divided into clinical and physical-dosimetric sections: clinical Indications, good practice in radiological exposures, devices, exposure parameters and modalities, patient positioning and immobilization, Reference Diagnostic Levels, operators and patient's radiation protection. Another important topic was the evaluation of the different incubators in order to understand if the consequences of the technological evolution have had an impact on the increase of the dose to the small patients, and how to choose the best device in terms of radiation protection. At the end the working group faced the problem of setting up the correct communication between clinicians and parents following the most recent indications of the international paediatric societies.

RESULTS

Taking into account the experience and expertise of 10 Italian Centres, the guideline sets out the criteria to ensure a high standard of neonatal care in NICU about procedures, facilities, recommended equipment, quality assurance, radiation protection measures for children and staff members and communication on radiation risk.

CONCLUSIONS

This document will allow a standardization of the approach to the exposures in NICU, although oriented to a flexible methodology.

A Large Skull Defect Due to Gorham-Stout Disease: Case Report and Literature Review on Pathogenesis, Diagnosis, and Treatment

A 24-year old man was referred to the Erasmus MC Bone Center because of an asymptomatic increasing skull defect of the left parietal bone. The defect was first noticed at the age of six, and gradually increased over the years. His medical history was unremarkable, without any known trauma and a negative family history for bone diseases. Laboratory tests showed a low vitamin D level without other abnormalities. Particularly, there was no increase in markers of inflammation or bone turnover. CT-scans of the skull showed an osteolytic region of the parietal skull bone, with a two-centimeter increase in diameter over 9 years. Contrast enhanced MRI showed lymphangiogenic invasion, which was compatible with our suspicion of Gorham-Stout disease. The patient was referred to the neurosurgeon for treatment with a bone graft while considering additional drug treatment. Gorham-Stout or vanishing bone disease is a rare entity characterized by progressive osteolysis with lymphangiogenic bone invasion. Although already reported in 1838, currently the diagnosis and treatment of Gorham-Stout disease is still challenging. The underlying pathophysiology is not clarified yet and several theories exist. The disease usually affects persons younger than 40 years and the majority present with bone disease of the maxillofacial region, the upper extremities or the torso. The clinical presentation includes most frequently pain, swelling, and functional impairment of the affected region, but the disease can also be asymptomatic. Laboratory investigations are usually normal, and diagnosis is based upon imaging and sometimes pathology examination of affected bone tissue. Treatment is experimental and there is no general consensus about the best option due to lack of randomized controlled trials. Case reports showed patients treated with bisphosphonates, interferon-alpha, anti-VEGF therapy, mTOR inhibitors, and radiotherapy. There are some reports of surgery with prosthetic or bone grafts but no long-term follow-up data exist. This paper describes a unique case of Gorham-Stout disease of the parietal skull bone and discusses the current state of knowledge about this rare bone disease.