Familial hemophagocytic lymphohistiocytosis type 4 (FHL4) with a rare STX11 genetic variation and leukoencephalopathy: a case report

Familial HLH (FHL), if untreated, has often a fatal outcome. 1 Neurological symptoms are seen in about two-thirds of FHL patients as a result of leptomeningeal and parenchymal infiltration by lymphocytes and macrophages, and suggest a poor prognosis. 2 We present the case of a four-year-old girl with familial hemophagocytic lymphohistiocytosis type 4 (FHL4) with a rare homozygous mutation of STX11 who was found to have leukoencephalopathy on neuroimaging. She had an unusual finding of low ferritin on initial evaluation that was misleading for the final diagnosis. CNS involvement portends a poor prognosis in HLH and must be kept in mind early in the diagnosis of FHL. Even in the presence of subtle symptoms, active investigation must be done in such cases as timely treatment is rewarded with good results.