Bone marrow necrosis and fat embolism syndrome in sickle cell disease: Increased susceptibility of patients with non-SS genotypes and a possible association with human parvovirus B19 infection

Les anémies aiguës et la stratégie transfusionnelle chez les drépanocytaires adultes

Worsening of anemia is very common in sickle cell disease. It is important to investigate specific complications related to sickle cell disease but also other causes of anemia in general. Transfusions or exchange transfusions are major therapeutic options and are frequently used for acute complications of sickle cell disease but also for primary and secondary prevention of some of the chronic complications. The transfusion strategy has been modified since the awareness of post-transfusion hemolysis by taking into account the transfusion risk score. A strong collaboration between the patient's expert center, the Blood center and the patient's hospitalization unit is required to make decisions. © 2023 Société nationale française de médecine interne (SNFMI). Published by Elsevier Masson SAS. All rights reserved.

A Rare Case of Progressive Encephalopathy in a Sickle Cell Trait Patient: A Case Report

Fat embolism syndrome (FES) is one of the underdiagnosed and underrecognized complications that can happen in multiple medical and surgical conditions. FES can manifest in a broad spectrum of signs and symptoms and affect multiple organ systems in the human body. One of the most commonly involved is the central nervous system (CNS), mainly the brain, which can be involved in different ways, and the presenting symptoms can vary in type and severity. One of the most common causes of FES is trauma, mainly a long bone fracture or any orthopedic injury. However, one of the rare causes of FES is sickle cell disease (SCD) and thalassemia. Generalized and vague presenting symptoms, the rarity of FES, and the absence of well-defined diagnostic criteria make it a challenging diagnosis for healthcare practitioners. FES diagnosis is usually made after having a high index of suspicion in patients with underlying risk factors that can precipitate and contribute to the pathophysiology of FES. Moreover, the diagnosis is usually reached after excluding other more common and treatable conditions.

Challenges in the diagnosis of thrombotic thrombocytopenic purpura

INTRODUCTION

Immune-mediated TTP (iTTP) is a rare condition without pathognomonic signs and symptoms. For this reason, the diagnosis of iTTP may be delayed or even missed, with potentially catastrophic consequences.

AREAS COVERED

The authors performed an extensive literature review on the diagnosis of iTTP and its challenges combined with their own experience in a referral center for patients with iTTP.

EXPERT OPINION

Although a definitive diagnosis of iTTP depends on the ADAMTS13 activity result, timely testing is rarely available at many centers to which patients present. If less complex tests were to become available, they would decrease the chances of late and/or missed diagnoses of iTTP throughout the world. While clinical scores to estimate the likelihood of iTTP exist, they are not well known, and can be misleading if used in the wrong context. Furthermore, the three scoring systems (PLASMIC, Bentley, and French) only moderately correlate with each other, which further complicates the landscape. The existence of these scores and how they should be used in practice is but one opportunity that can be seized through more robust programs to educate nonspecialist clinicians on how to recognize and treat patients with iTTP.

Bone marrow embolism: should it result from traumatic bone lesions? A histopathological human autopsy study

Bone marrow embolism (BME) is likely a consequence of fractures in which pulmonary vessels are the most affected. However, some cases of BME were reported in the absence of trauma. Thus, a traumatic injury might not be necessary for developing BME. This study discusses BME cases in patients without signs of fractures or blunt trauma. The discussion addresses various possible mechanisms for the appearance of BME. Options include cancer in which bone marrow metastasis is a suggestive cause. Another proposal is the chemical theory where bone marrow fats are released via lipoprotein lipase in a pro-inflammatory state, resulting in vascular/pulmonary obstruction. Other cases discussed in this study are hypovolemic shock and drug-abuse related BME. All autopsy cases with BME were included regardless of the cause of death for a period of 2 years. Autopsies involved complete dissection with the macroscopic evaluation of the affected organs, including the heart, lungs, and brain. Tissues were also prepared for microscopic examination. Of the 11 cases, eight showed non-traumatic BME (72%). These findings conflict with theories in the literature that BME most commonly occurs after fractures or trauma. One of the eight cases exhibited mucinous carcinoma; one is presented with hepatocellular carcinoma; and two cases showed severe congestion. Lastly, one case was found to be associated with each of the following conditions: liposuction, drug abuse, pulmonary hypertension, and heart failure. Each case suggests a different pathophysiology for developing BME, yet the exact mechanisms are not fully understood. Further study of non-traumatic associated BME is recommended.

Mortality Rates and autopsy findings in fat embolism syndrome complicating sickle cell disease

Fat embolism syndrome is a rare but underdiagnosed complication of sickle cell disease associated with high morbidity and mortality. It affects predominantly patients with a previously mild course of their illness and those of non-SS genotypes while there is possibly an association with infection with human parvovirus B19 (HPV B19). Here, we present the mortality rates and autopsy findings of all reported cases to date. A systematic review has revealed 99 published cases in the world literature with a mortality rate of 46%. Mortality varied greatly according to the time of reported cases with no survivors in the 1940s, 1950s or 1960s and no deaths since 2020. 35% of cases had previously undiagnosed sickle cell disease and the latter was only identified at autopsy after developing fat embolism with a fatal outcome. 20% of cases reported after 1986 tested positive for HPV B19 with an associated mortality of 63% whereas in cases that have not documented HPV B19 infection the mortality was 32%. The organs most often staining positive for fat were the kidneys, lungs, brain and heart whereas ectopic haematopoietic tissue was found in 45% of the examined lung specimens.

Bone marrow necrosis and fat embolism syndrome in sickle cell disease during COVID-19 infection treated successfully with sequential red cell and plasma exchange

Fat embolism syndrome (FES) is a rare life-threatening condition that is particularly seen in milder forms of sickle cell disease (SCD). Widespread systemic fat emboli are generated in the context of extensive bone marrow necrosis. Multi-organ failure with a high morbidity and mortality may quickly develop. Infection with Parvovirus B19 is a common precipitant. Here, the authors report the case of a 35-year-old Afro-Caribbean man with HbSC disease who presented with FES having tested positive for SARS-COV-2. He rapidly became critically ill and required admission to the intensive care unit for organ support. He was treated with red cell exchange and plasma exchange and made a good recovery to leave hospital at week 7.

Stroke in sickle cell disease and the promise of recent disease modifying agents

Sickle cell disease (SCD) is an inherited hemoglobinopathy affecting approximately 100,000 individuals in the United States. Cerebrovascular disease is among the most common and debilitating complications of SCA, with 53% experiencing silent cerebral infarct by age 30 and 3.8% experiencing overt stroke by age 40 years. This review highlights the burden of cerebrovascular disease in SCD, including both stroke and silent cerebral infarct (SCI). We then discuss the pathophysiology of stroke and cerebral fat embolism in the absence of a patent foramen ovale. This review also reveals that options for primary and secondary stroke prevention in SCD are still limited to hydroxyurea and blood transfusion, and that the role of aspirin and anticoagulation in SCD stroke has not been adequately studied. Limited data suggest that the novel disease-modifying agents for SCD management may improve renal dysfunction, leg ulcers, and lower the abnormally high TCD flow velocity. Further research is urgently needed to investigate their role in stroke prevention in SCD, as these novel agents target the main stroke contributors in SCD - hemolysis and vaso-occlusion. This literature review also explores the role of healthcare disparities in slowing progress in SCD management and research in the United States, highlighting the need for more investment in patient and clinician education, SCD management, and research.

Pitfalls in Diagnosing Thrombotic Thrombocytopenic Purpura in Sickle Cell Disease

Thrombotic thrombocytopenia purpura is characterised by microangiopathic haemolytic anaemia and red cell fragmentation on the peripheral smear, neurological involvement and thrombocytopenia. Diagnosis in the context of sickle cell disease can be challenging due to the inherent haemolytic state and the multitude of other associated complications of the latter. Specifically, fat embolism syndrome characterised by respiratory failure, neurological impairment and thrombocytopenia can be misdiagnosed this way. Confirmation of a diagnosis of thrombotic thrombocytopenic purpura requires demonstration of very low levels (<10%) of the metalloproteinase ADAMTS13 which in fat embolism syndrome is normal. Existing scoring systems used to estimate the pre-test probability for thrombotic thrombocytopenic purpura cannot be applied in patients with sickle cell disease due to the chronic underlying haemolysis. Here, we analyse the diagnostic approach in published cases of thrombotic thrombocytopenic purpura affecting patients with sickle-cell disease. The vast majority of cases were characterised by severe respiratory failure before any other manifestation, a feature of fat embolism syndrome but not of thrombotic thrombocytopenic purpura, and all received red cell transfusion prior to receiving therapeutic plasma exchange. Despite the potential overestimation of the pre-test probability using the existing scoring systems, a large number of cases still scored low. There were no cases with documented low ADAMTS13. In the majority this was not tested, while in the 3 cases that ADAMTS13 was tested, levels were normal. Our review suggests that due to many overlapping clinical and laboratory features thrombotic thrombocytopenic purpura may be erroneously diagnosed in sickle cell disease instead of other complications such as fat embolism syndrome and confirmation with ADAMTS13 testing is essential.

[Parvovirus B19 infections in adults]

Acute Parvovirus B19 (PVB19) infection is responsible for erythema infectiosum in children and non-specific polyarthralgias in immunocompetent adults associated with skin lesions and rarer manifestations (hepatic, neurological, cardiac or nephrological). In immunocompromised patients, cytopenias are more frequent and in some cases, viremia persists and is responsible for PVB19 chronic infection. PVB19 is responsible for pure red cell aplasia during chronic hemolytic diseases. Acute PVB19 infection is a differential diagnosis of some autoimmune diseases and has been suspected to be a trigger for some autoimmune diseases because of its ability to promote the emergence of autoimmune markers. Mechanisms of molecular mimicry, induction of apoptosis and activation of enzymes have been demonstrated, explaining in part the production of autoantibodies during infection. However, the demonstration of a causal relationship in the triggering of autoimmune disease remains to be done. This review provides a synthesis of the PVB19 infection clinical data in adults with a particular focus on these links with autoimmunity.

Identifying and Treating Severe Bone Marrow Necrosis and Fat Embolism Syndrome in Pediatric Patients With Sickle Cell Disease: A Case Report

Fat embolism syndrome after bone marrow necrosis is an extremely rare complication in sickle cell disease associated with significant morbidity and mortality. A high index of suspicion is required for diagnosis. This case report will assist pediatric clinicians and hematologists to recognize this severe complication in patients with sickle cell disease and to promptly initiate treatment. Red flags include severe bone pain, respiratory distress, neurological impairment, decreasing platelet count, peripheral leukocyte left shift, elevated nucleated red blood cells, and significant elevation in plasma ferritin and lactate dehydrogenase. We report a pediatric patient who was diagnosed early, received urgent red cell exchange transfusion and plasma exchange, and ultimately survived this devastating complication.

Management of acute chest syndrome in patients with sickle cell disease: a systematic review of randomized clinical trials

INTRODUCTION

Acute chest syndrome (ACS) accounts for the highest mortality in Sickle cell disease patients. Early diagnosis and timely management of ACS results in better outcomes. However, the effectiveness of most treatment modalities for ACS management has not been established.

AREAS COVERED

To review the treatment modalities management protocols and highlight the effectiveness of each option a literature search was done. Randomized controlled trials that assessed the efficacy of different treatment modalities in ACS management in SCD patients were chosen and reviewed.

EXPERT OPINION

11 randomized controlled trials were found that evaluated the efficacy of incentive spirometry, positive expiratory pressure device, intravenous dexamethasone, oral vs. intravenous morphine, inhaled nitric oxide, unfractionated heparin, and blood transfusion in the prevention or treatment of ACS. Although there are guidelines for ACS treatment, the available evidence is very limited to delineating the effectiveness of various interventions in ACS management. More high-quality studies and trials with a larger patient population can benefit this area to support the recommendations with stronger evidence.

Sickle cell disease and fat embolism: a rare complication of vaso-occlusive crisis

A 61-year-old woman was admitted to the hospital for management of a painful vaso-occlusive crisis. She had a history of sickle cell beta-thalassaemia and end-stage renal disease managed with intermittent haemodialysis. While hospitalised, she became lethargic and unresponsive and developed acute chest syndrome. Initial MR scan of brain, cerebrospinal fluid examination and continuous electroencephalogram were unremarkable, but subsequent MR scan of brain identified a right transverse venous sinus thrombosis and extensive supratentorial and infratentorial microhaemorrhages consistent with fat emboli. We; therefore, discuss a case of non-traumatic fat embolism syndrome, a rare complication of sickle cell disease.

Acute chest syndrome of sickle cell disease: genetics, risk factors, prognosis and management

IntroductionSickle cell disease, one of the world's most prevalent Mendelian disorders, is a chronic hemolytic anemia punctuated by acute vasoocclusive events. Both hemolysis and vasoocclusion lead to irreversible organ damage and failure. Among the many sub-phenotypes of sickle cell disease is the acute chest syndrome (ACS) characterized by combinations of chest pain, cough, dyspnea, fever, abnormal lung exam, leukocytosis, hypoxia, and new radiographic opacities. ACS is a major cause of morbidity and mortality.Area coveredWe briefly review the diagnosis, epidemiology, etiology, and current treatments for ACS and focus on understanding and estimating the risks for developing this complication, how prognosis and outcomes might be improved and the genetic elements that might impact the risk of ACS.Expert opinionThe clinical heterogeneity of ACS has hindered our understanding of risk stratification. Lacking controlled clinical trials most treatment is based on expert opinion. Fetal hemoglobin levels and coexistent α thalassemia affect the incidence of ACS; other genetic associations are tenuous. Transfusions, whose use not innocuous, should be targeted to the severity and likelihood of ACS progression. Stable, non-hypoxic patients with favorable hematologic and radiographic findings usually do not need transfusion; severe progressive ACS is best managed with exchange transfusion.

A Case of Fat Embolism Syndrome with Cerebral Involvement in Sickle Cell Anemia

Fat embolism syndrome (FES) is a rare condition that can occur as a complication of sickle cell disease. We describe a case of a patient with sickle cell disease (homozygous Hb S or HBB: c.20A>T) presenting with initial signs and symptoms consistent with a vaso-occlusive crisis (VOC). Within 24 hours, the patient developed evidence of coagulopathy, multi organ failure and a reduced level of consciousness (LOC) prompting intubation. A diagnosis of FES was made on the basis of the patient's clinical presentation, in conjunction with magnetic resonance imaging (MRI) of the brain revealing innumerable tiny foci of restricted diffusion, intracytoplasmic microvesicular fat on Sudan Red staining of bronchoalveolar lavage samples and evidence of a pulmonary shunt on echocardiogram bubble study. Red blood cell (RBC) exchange transfusion was initiated 3 days following initial presentation and no further exchange transfusions were needed on the basis of subsequent Hb S (HBB: c.20A>T) levels. The LOC gradually improved and the patient was extubated 12 days following presentation. Neurological improvement was slow, with mild cognitive impairment initially evident at 3 months and no cognitive or neurological deficits remaining within 6 months of admission. This case highlights the importance of understanding the pathophysiology and clinical presentation of FES, as early exchange transfusion may improve survival in patients with sickle cell disease and FES.

A Rare and Successfully Managed Complication of Stem Cell Transplantation in an Adult Patient With Sickle Cell Disease: Bone Marrow Necrosis

Sickle cell disease is the most common genetic disorder in the Eastern Mediterranean region where our transplant center is located. Today, adult patients with sickle cell disease can also be successfully treated with allogeneic hematopoietic stem cell transplantation. Bone marrow necrosis is a rare and serious clinical condition. Herein, we present this complication for the first time in the literature, which developed in the course of allogeneic hematopoietic stem cell transplantation and was successfully managed with additional bone marrow support. The recognition, prevention, and management of this rare and potentially fatal complication, bone marrow necrosis, are vitally important, especially in regions with high prevalence of sickle cell disease.

Complete neurological recovery from fat embolism syndrome in sickle cell disease after sequential red cell exchange transfusion and therapeutic plasma exchange

Fat embolism syndrome in sickle cell disease is associated with great mortality, while more than half of survivors suffer severe neurological sequelae. Release of fat droplets leads to obstruction of the microcirculation as well as generation of proinflammatory cytokines that can cause direct tissue injury. Red cell exchange transfusion can be life-saving but the addition of therapeutic plasma exchange may further improve outcomes by removing such inflammatory mediators. Here, we describe the case of a 27-year-old male patient with sickle cell anaemia presenting with typical features of fat embolism syndrome including neurological involvement with greatly reduced level of consciousness. MRI of his brain showed multiple widespread microhemorrhages giving the characteristic "star field" pattern but also a cytotoxic lesion of the corpus callosum, known to be the result of direct neurotoxicity by proinflammatory cytokines. The patient underwent emergency red cell exchange transfusion leading only to modest clinical improvement but fully regained consciousness after three cycles of therapeutic plasma exchange. This case highlights the deleterious effect of the hyperinflammatory state characteristic of many sickle cell complications and supports further exploring the potential benefit from plasma exchange as an adjunct to red cell exchange in order to remove proinflammatory cytokines during acute complications of sickle cell disease.

Qualitative and quantitative magnetic resonance imaging evaluation of bone tissue vaso-occlusive events in patients with sickle cell disease

OBJECTIVE

To evaluate the association between bone changes due to vaso-occlusive events in sickle cell disease (SCD) revealed by conventional MRI sequences and the fat fraction obtained using a 6-point DIXON technique (FFdix), in an attempt to use quantitative data as a biomarker for bone complications.

METHODS

Cross-sectional study, with 48 SCD patients, 26-homozygous (HbSS), and 22-compound heterozygous (HbSC). Forty-eight healthy individuals paired by age, weight, and sex with SCD patients. All participants underwent lumbar spine and pelvis MRI. Conventional sequences: bone complications related to vaso-occlusive events-femoral head avascular necrosis, bone infarctions, "H"-shaped vertebrae, bone marrow necrosis. Six-point DIXON technique: quantitative evaluation of the bone marrow at pre-established sites (lumbar vertebrae, sacrum, iliacs, femoral heads, greater femoral trochanters, femoral necks). Pearson's correlation, ROC curve, and binary logistic regression analysis were performed.

RESULTS

The most frequent findings in the SCD group included femoral head avascular necrosis (75%), bone infarctions (58.3%), "H"-shaped vertebrae (58.3%), and typical imaging findings of bone marrow necrosis (8.3%). Cortical bone thickness in the proximal femoral diaphysis in patients with SCD was moderately negatively correlated with FFdix in lumbar vertebrae, iliacs, femoral necks, and first sacral vertebrae. The ROC curves and odds ratios demonstrated excellent performance of FFdix in all the evaluated anatomical sites and identified patients having bone complications.

CONCLUSIONS

FFdix could serve as a potential biomarker in SCD because of its association with bone complications secondary to vaso-occlusive events in patients with SCD, especially in femoral heads, femoral necks, and iliacs.

Fat Embolism Syndrome in Sickle Cell β-Thalassemia Patient With Osteonecrosis: An Uncommon Presentation in a Young Adult

Fat embolism syndrome is a relatively infrequent presentation in sickle cell thalassemia patients. It most commonly occurs in long bone fractures in the setting of trauma. However, nonorthopedic trauma and nontraumatic cases have been reported to contribute to fat embolism. The fat embolic syndrome is an underdiagnosed, life-threatening, and debilitating complication of sickle-β-thalassemia–related hemoglobinopathies. It is primarily seen in milder versions of sickle cell disease, including HbSC and sickle cell β-thalassemia, with the mild prior clinical course without complications; hence, diagnosis can be easily missed. Pathogenesis of fat embolic syndrome is a combination of mechanical obstruction from fat globules released into systemic circulation at the time of bone marrow necrosis and direct tissue toxicity from fatty acids and inflammatory cytokines released from fat globules. Prompt diagnosis and early initiation of treatment can reduce morbidity and mortality and result in better outcomes and prognosis. Red cell exchange transfusion is the mainstay of therapy with mortality benefits. Overall mortality and neurological sequelae continue to be high despite increased red cell exchange transfusion in the last few years. In this article, we discussed a case of a 34-year-old male patient with a history of sickle cell thalassemia and avascular necrosis of the hip, who presented with fever, hypoxia, encephalopathy, and generalized body aches, found to have thrombocytopenia and punctate lesions on magnetic resonance imaging brain, which led to the diagnosis of the fat embolism syndrome. Only a few sickle cell β-thalassemia with fat embolic syndrome cases have been reported.

Fat Embolism Syndrome - A Qualitative Review of its Incidence, Presentation, Pathogenesis and Management

Fat Embolism Syndrome (FES) is a poorly defined clinical phenomenon which has been attributed to fat emboli entering the circulation. It is common, and its clinical presentation may be either subtle or dramatic and life threatening. This is a review of the history, causes, pathophysiology, presentation, diagnosis and management of FES. FES mostly occurs secondary to orthopaedic trauma; it is less frequently associated with other traumatic and atraumatic conditions. There is no single test for diagnosing FES. Diagnosis of FES is often missed due to its subclinical presentation and/or confounding injuries in more severely injured patients. FES is most frequently diagnosed using the Gurd and Wilson criteria, like its rivals it is not clinically validated. Although FES is a multi-system condition, its effects in the lung, brain, cardiovascular system and skin cause most morbidity. FES is mostly a self-limiting condition and treatment is supportive in nature. Many treatments have been trialled, most notably corticosteroids and heparin, however no validated treatment has been established.

Diverse manifestations of a sickle cell crisis

We describe the case of a 21-year-old man with a background of sickle cell disease (SCD) who was on acute presentation in a sickle cell crisis required immediate intensive care admission with red blood cell exchange and ventilatory support. He had right frontal lobe infarcts and extensive bilateral deep white matter lesions most likely secondary to fat embolism. Inpatient investigations demonstrated a patent foramen ovale, explaining the route of spread of the fat embolus. He then had a transcatheter closure of the atrial defect. The patient needed prolonged inpatient rehabilitation. He was discharged from hospital in a wheelchair secondary to severe lower limb neurology and bilateral knee heterotopic ossification. He lives with the possibility of early onset dementia and cognitive decline, requiring constant care. The case highlights the multiple manifestations of SCD and their diverse and debilitating consequences.

Neuroimaging in Sickle Cell Disease: A Review

Sickle cell disease is the most common hereditary hemoglobinopathy, which results in abnormally shaped and rigid red blood cells. These sickle-shaped red blood cells cause vaso-occlusion and ischemic phenomena that can affect any organ in the body. As a common cause of disability, the neurological manifestations of sickle cell disease are particularly important. Neuroimaging has a crucial role in the diagnosis, management, and prevention of the complications of sickle cell disease. These complications can affect the brain parenchyma, vasculature, and skull and can be ascribed directly or indirectly to a vasculopathy of small and large vessels. Vaso-occlusion can cause ischemic stroke. Ischemic damage in the absence of an acute neurological deficit, and therefore only apparent on neuroimaging, is termed silent cerebral ischemia. Weakening of the arterial walls can cause aneurysms. In its most severe form, a vasculopathy of the terminal internal carotid arteries can progress to moyamoya syndrome, characterized by steno-occlusive disease and the formation of friable collateral arteries. Rupture of aneurysms or friable collateral arteries is a potential cause of intracranial hemorrhage. The skull and vertebrae may be affected by extra-medullary hematopoiesis, due to severe anemia, or iron deposition, due to chronic red blood cell transfusion. Impaired blood supply to bone is associated with osteomyelitis and osteonecrosis. Fat embolization syndrome is a rare complication of osteonecrosis, which may cause devastating neurological impairment. Awareness and early recognition of the diverse manifestations of sickle cell disease on neuroimaging is crucial to ensure optimal treatment in a complex patient cohort.

Bone marrow necrosis and fat embolism syndrome: a near fatal complication in previously undiagnosed sickle beta + thalassaemia

Prevalence of haemoglobin sickle-β⁺ thalassaemia (Hb S/β+thal) is variable with geography ranging from 0.2% to 10% among sickle cell patients. Clinical presentation of Hb S/β+thal patients depends on HbA level, with milder disease often going undiagnosed. However, rarely these patients can present with a fulminant vaso-occlusive crisis (VOC). Given VOC can present with non-specific symptoms, the diagnosis and treatment is often delayed. Here, we present a patient who initially developed altered mental status, pancytopenia and multiorgan failure due a critical VOC resulting in bone marrow necrosis and fat embolism. Subsequent workup confirmed that our patient had Sickle-β⁺ thalassaemia, which had gone undiagnosed, despite subclinical evidence of haemolysis on routine lab work for years. Following diagnosis and initiation of RBC exchange, he improved significantly and was discharged home. High index of suspicion and bone marrow biopsy is vital for early diagnosis and management of this rare condition.

Hyperhaemolytic Syndrome in Sickle Cell Disease: Clearing the Cobwebs

Sickle cell disease (SCD) presents with a dynamic background of haemolysis and deepening anaemia. This increases the demand for transfusion if any additional strain on haemopoiesis is encountered due to any other physiological or pathological causes. Patients with cerebrovascular accidents are placed on chronic blood transfusion; those with acute sequestration and acute chest syndrome are likewise managed with blood transfusion. These patients are prone to develop complications of blood transfusion including alloimmunization and hyperhaemolytic syndrome (HHS). This term is used to describe haemolysis of both transfused and "own" red cells occurring during or post-transfusion in sickle cell patients. Hyperhaemolysis results in worsening post-transfusion haemoglobin due attendant haemolysis of both transfused and autologous red cells. The mechanism underlying this rare and usually fatal complication of SCD has been thought to be secondary to changes in the red cell membrane with associated immunological reactions against exposed cell membrane phospholipids. The predisposition to HHS in sickle cell is also varied and the search for a prediction pattern or value has been evasive. This review discusses the pathogenesis, risk factors and treatment of HHS, elaborating on what is known of this rare condition.

Red blood cell exchange in an emergency in sickle cell disease

Red blood cell exchange (RBCEx) has become a standard therapy to remove abnormal red blood cells (RBCs) in patients with sickle cell disease (SCD). In the last few decades, numerous RBCEx procedures have been performed chronically during regular programs, while numerous procedures have also been performed in an emergency for several indications, this therapeutic option being very efficient in vital and emergency situations. In both groups of indications, large amounts of sickle RBCs have to be removed, which requires great precision and the setting of specific hematological targets. The aim of this review is to discuss the aims, clinical and biological targets, and the requirements and precautions when performing RBCEx in an emergency. Moreover, we analyze how improvement of the techniques as well as the clinical and biological targets has led to optimization of the procedures in emergency settings. We also consider the outstanding issues that require additional investigation.

Fat Embolism Syndrome in Sickle Cell Disease

Fat embolism syndrome is a devastating complication of sickle cell disease resulting from extensive bone marrow necrosis and associated with high mortality rates, while survivors often suffer severe neurological sequelae. Despite that, the syndrome remains under-recognised and under-diagnosed. Paradoxically, it affects exclusively patients with mild forms of sickle cell disease, predominantly HbSC and HbSβ⁺. A significant number of cases occur in the context of human parvovirus B19 infection. We provide here a brief summary of the existing literature and describe our experience treating 8 patients in our institution. One patient had HbSS, 6 HbSC and 1 HbSβ⁺. All patients developed type I respiratory failure and neurological involvement either at presentation or within the first 72 h. The most striking laboratory abnormality was a 100-fold increase of the serum ferritin from baseline. Seven patients received emergency red cell exchange and 1 simple transfusion. Two patients (25%) died, 2 patients (25%) suffered severe neurological impairment and 1 (12%) mild neurological impairment on discharge, while 3 (38%) patients made a complete recovery. With long-term follow-up, 1 patient with severe neurological impairment and one patient with mild neurological impairment made dramatic improvements, making the long-term complete recovery or near complete recovery rate 63%. Immediate red cell exchange transfusion can be lifesaving and should be instituted as soon as the syndrome is suspected. However, as the outcomes remain unsatisfactory despite the increasing use of red cell exchange, we suggest additional therapeutic measures such as therapeutic plasma exchange and pre-emptive transfusion for high risk patients.

Neurologic recovery in systemic nontraumatic fat embolism syndrome in an elderly patient with hemoglobin SC disease: A case report

Cerebral fat embolism syndrome is an under-recognized yet well-known complication of bone marrow necrosis occurring in patients with sickle cell disease. We highlight a case manifested by multisystem organ failure in an elderly patient who attained neurologic recovery with prompt initiation of hematology consultation, RBC exchange, and supportive measures.

Dengue in hospitalized children with sickle cell disease: A retrospective cohort study in the French departments of America

BACKGROUND

To describe the characteristics of dengue in sickle cell children and try to identify risk factors of severity.

METHODS

In this retrospective study, we describe the evolution according to genotype (SS or SC and controls) and severity.

RESULTS AND CONCLUSIONS

From 2005 to 2013, 106 hospitalizations for dengue fever were recorded, 35 SS genotype, 35 SC and 36 without SCD or any other chronic disease. The clinical evolution was quite different. During hospitalization, SC patients were more likely to develop multiorgan failure (31.4% versus 25.7% for SS, and 0% for controls, p=0.001), or acute pulmonary complications than patients without SC sickle cell disease (14.3% versus 8.6% for SS, and 0% for controls, p=0.03). Level 3 analgesic treatment was more frequent in SC patients (22.9% versus 3% for SS, and 0% for controls, p<0.001). Patients with SC sickle cell disease had a higher proportion of severe forms of dengue (57.1% versus 37.1% for SS, and 0% for controls, p<0.001) than patients without SC sickle cell disease. Transfer in intensive care unit was required for most SC patients (22.9% versus 3% for SS, and 0% for controls, p=0.005).Fatal episodes were more frequent in SC patients than in patients without SC sickle cell disease (5 deaths versus 1 for SS and 0 for controls, p=0.02). Thirty-three patients (47.1%) were diagnosed as having severe dengue (13 SS and 20 SC). On univariate analysis, age >10 years, acute pulmonary complications, multiorgan failure, severe anemia requiring transfusion, use of antibiotic treatment, need for treatment with morphine, and longer hospital stay were statistically more frequent in severe dengue-associated cases. Multiple logistic regression analysis showed that HbSC genotype and acute pulmonary complications, were significantly associated with severe dengue. In the multivariate model, the area of the ROC curve was 0.831. Children with SC genotype, typically thought to have less severe disease, actually had a higher rate of severe dengue and death than those with SS genotype.

Vascular Instability and Neurological Morbidity in Sickle Cell Disease: An Integrative Framework

It is well-established that patients with sickle cell disease (SCD) are at substantial risk of neurological complications, including overt and silent stroke, microstructural injury, and cognitive difficulties. Yet the underlying mechanisms remain poorly understood, partly because findings have largely been considered in isolation. Here, we review mechanistic pathways for which there is accumulating evidence and propose an integrative systems-biology framework for understanding neurological risk. Drawing upon work from other vascular beds in SCD, as well as the wider stroke literature, we propose that macro-circulatory hyper-perfusion, regions of relative micro-circulatory hypo-perfusion, and an exhaustion of cerebral reserve mechanisms, together lead to a state of cerebral vascular instability. We suggest that in this state, tissue oxygen supply is fragile and easily perturbed by changes in clinical condition, with the potential for stroke and/or microstructural injury if metabolic demand exceeds tissue oxygenation. This framework brings together recent developments in the field, highlights outstanding questions, and offers a first step toward a linking pathophysiological explanation of neurological risk that may help inform future screening and treatment strategies.

Advances in the Development of Antiviral Strategies against Parvovirus B19

Parvovirus B19 (B19V) is a human pathogenic virus, responsible for an ample range of clinical manifestations. Infections are usually mild, self-limiting, and controlled by the development of a specific immune response, but in many cases clinical situations can be more complex and require therapy. Presently available treatments are only supportive, symptomatic, or unspecific, such as administration of intravenous immunoglobulins, and often of limited efficacy. The development of antiviral strategies against B19V should be considered of highest relevance for increasing the available options for more specific and effective therapeutic treatments. This field of research has been explored in recent years, registering some achievements as well as interesting future perspectives. In addition to immunoglobulins, some compounds have been shown to possess inhibitory activity against B19V. Hydroxyurea is an antiproliferative drug used in the treatment of sickle-cell disease that also possesses inhibitory activity against B19V. The nucleotide analogues Cidofovir and its lipid conjugate Brincidofovir are broad-range antivirals mostly active against dsDNA viruses, which showed an antiviral activity also against B19V. Newly synthesized coumarin derivatives offer possibilities for the development of molecules with antiviral activity. Identification of some flavonoid molecules, with direct inhibitory activity against the viral non-structural (NS) protein, indicates a possible line of development for direct antiviral agents. Continuing research in the field, leading to better knowledge of the viral lifecycle and a precise understanding of virus–cell interactions, will offer novel opportunities for developing more efficient, targeted antiviral agents, which can be translated into available therapeutic options.

Histopathological evaluation of autopsy cases with isolated pulmonary fat embolism (IPFE): is cardiopulmonary resuscitation a main cause of death in IPFE?

Background: Fat embolism (FE) may develop following many traumatic and atraumatic clinical conditions; however, fewer data exist regarding the occurrence of isolated pulmonary FE (IPFE). Cardiopulmonary resuscitation (CPR) is an emergency procedure for maintaining blood circulation and oxygenation during cardiac arrest. In this study, we aimed to evaluate the association of CPR with IPFE in autopsy cases.

Methods: A total 402 cases among 4,118 autopsies were diagnosed with IPFE, and the medical background of these cases was retrospectively evaluated. Diagnosis of FE and FE grading were performed with histopathological examinations of postmortem tissue samples, and injury-severity scores of traumatic cases were assessed. Data of traumatic and atraumatic cases were statistically compared.

Results: Of the IPFE cases, 298 (741%) were male and 104 (25.9%) female, with overall mean age 53.7 (2–99) years. Causes of death of studied subjects were traumatic for 302 (75.1%) and atraumatic reasons for 100 (24.9%) cases. CPR was performed for 277 cases of which 177 (63.9%) were traumatic and 100 (36.1%) were non-traumatic. In comparison to traumatic cases, significantly higher CPR frequency was determined in atraumatic IPFE (P=0.001). High grade FE in the traumatic cases, and mild-moderate grade of FE in the nontraumatic cases were found statistically significant (P=0.001).

Conclusion: This study indicates that CPR may be one of the leading factors in the development of IPFE in atraumatic conditions, and this procedure was related to mild–moderate IPFE manifestations. Regardless of whether conditions were traumatic or atraumatic, in patients who survive following CPR for manifest ventilation/perfusion problems, it should be remembered that IPFE may have developed due to CPR.

Clinical impact & pathogenic mechanisms of human parvovirus B19: A multiorgan disease inflictor incognito

Human parvovirus B19 (B19V) causes myriads of clinical diseases; however, owing to lack of awareness and undetermined clinical impact, it has failed to become a virus pathogen of global concern. Cryptically, B19V causes significant morbidity and mortality. Half of the world population and 60 per cent of Indians are known to be serologically naive and are at risk of acquiring B19V infections. Cumulatively, our data showed 21.3 per cent B19V-infected patients with juvenile chronic arthropathy, recurrent abortions, multi-transfused thalassaemia and leukaemia. In addition, B19V-infected cases that ended fatally included patients with pure red cell aplasia, fulminant hepatitis and haemophagocytic syndrome. Novel clinical associations of B19V observed were amegakaryocytic thrombocytopaenia, myositis and non-occlusive ischaemic gangrene of bowel. B19V possesses multiple receptors which are distributed widely in human tissues. Vascular endothelial cell infection by B19V causes endothelialitis and vasculitic injuries besides antibody-dependent enhancement which empowered B19V to cause multiorgan diseases. Owing to lack of suitable animal model for B19V, true causal role remains to be determined, but numerous reports on B19V infections substantiate a causal role in multiorgan diseases. Hence, B19V infections need to be recognized, investigated and treated besides making efforts on vaccine developments.

Recommendations for the use of red blood cell exchange in sickle cell disease

Sickle cell disease (SCD) is a genetic disorder characterised by a single mutation of the beta globin gene, causing the production of an abnormal haemoglobin called sickle haemoglobin (HbS). In its deoxygenated form, HbS polymerises, causing major rheological disorders, which presents clinically as periodic vaso-occlusive crises, chronic haemolysis and chronic vascular dysfunction. Patients often resort to a background treatment, and transfusion remains the cornerstone in the management of the disease, significantly reducing morbidity and mortality. The aim of red blood cell exchange (RBCX) is to improve tissue oxygenation by increasing haemoglobin levels while lowering HbS levels. RBCX can be performed by manual or automated exchange, and each technique has its own set of advantages and disadvantages. This article will outline the transfusion indications for the main complications of SCD, as well as the most appropriate strategy to use.

Fat Embolism Syndrome

Fat embolisms are fat globules that enter the circulatory system, typically through trauma, that may or may not lead to the development of fat embolism syndrome (FES), a rare and ill-defined diagnosis that can cause multiorgan failure and death. The exact mechanism of FES remains unknown, although several theories support the involvement of inflammatory response activation that contributes to characteristic clinical findings. There is no gold standard for diagnosis of FES, and treatment at this time remains primarily supportive. Early recognition of FES symptoms is the most beneficial nursing intervention for combating this serious disorder.

Care of the Critically Ill Pediatric Sickle Cell Patient

Sickle cell disease is the most common inherited disease in the United States. Through the effects of hemolysis and vaso-occlusion, it has the potential to incite critical illness involving multiple organ systems. Children with sickle cell disease are at risk of multiple types of shock resulting in a need for ICU care. Our youngest patients with sickle cell disease are at highest risk of infection due to lack of splenic function, and this can present with septic shock. Hypovolemic shock can occur secondary to severe acute anemia as seen with splenic sequestration or a delayed transfusion reaction. As one ages, the risk of cardiac dysfunction – diastolic and systolic dysfunction as well as pulmonary hypertension – can result in cardiogenic shock. In addition to shock, patients with sickle cell disease are at risk for respiratory failure from acute chest syndrome as well as acute neurologic deterioration from stroke. For these reasons, critical care physicians must be familiar with the unique management of sickle cell complications in order to provide the best possible care for this vulnerable population.

Cerebral fat embolism syndrome in sickle cell disease without evidence of shunt

Fat embolism syndrome (FES) is a known complication of sickle cell disease (SCD) that occurs secondary to vaso-occlusive crises, bone marrow infarction, and the subsequent release of fat globules into the venous circulation. Although neurologic involvement is common, the pathophysiology of cerebral fat emboli remains controversial. While fat microemboli can enter the arterial circulation through right-to-left shunts, the systemic release of free fatty acids may also cause indirect endothelial damage and disruption of the blood-brain-barrier. We present an unusual case of cerebral fat emboli in SCD that occurred in the absence of acute chest syndrome or right-to-left shunt, favoring a biochemical etiology. Treatment of FES includes supportive care and emergent red cell exchange transfusions.

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Cerebral fat embolism syndrome is a rare complication of sickle cell disease.

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Brain MRI shows multifocal punctate infarcts and hemorrhages in a “starfield” pattern.

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Fat microemboli can enter the brain through intrapulmonary or intracardiac shunts.

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In the absence of shunting, free fatty acids may cause indirect endothelial damage.

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Treatment involves supportive care and red cell exchange transfusions.