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

Successful therapeutic plasma exchange for a patient with sickle cell disease and fat embolism syndrome after a failure of a response to red cell exchange transfusion

BACKGROUND

Fat embolism syndrome (FES) is a rare complication, which was reported mostly with milder forms of heterozygous sickle cell disease (SCD). It may present in a catastrophic way with multi-organ failure, particularly involving the pulmonary and neurological systems. Diagnosis is often missed or delayed; and the standard recommended treatment is red cell exchange (RCE) transfusion, which has sub-optimal results, such as debilitating long-term neurological complications. Recently, few reports suggested that the addition of Therapeutic Plasma Exchange (TPE) might further improve the outcome.

CASE DESCRIPTION

A 23-year-old woman with homozygote SCD was admitted with bony pains and vaso-occlusive crises. However, her course evolved to respiratory failure requiring mechanical ventilation, decreased level of consciousness, skin rash, severe anemia and thrombocytopenia and a picture consistent with thrombotic microangiopathy. MRI of the brain showed scattered multi-focal ischemic foci and cytotoxic edema. The patient received RCE on the third day after admission without improvement. On the seventh day, TPE was instituted (2 L/day of fresh frozen plasma for 5 days), following which she regained her consciousness and showed an improvement in her laboratory abnormalities. On follow up, she had gradual full neurological recovery and resolution of the MRI findings within a few months.

CONCLUSION

FES remains a diagnostic and therapeutic challenge, with significant morbidity and mortality. Success in the management of this reported case with the addition of TPE to RCE supports the notion that TPE may be a potentially helpful modality that deserves further 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.