Near fatal cerebellar swelling in familial hemophagocytic lymphohistiocytosis.

We describe a 3 year-old male who presented with fever and cerebellar dysfunction after varicella. He developed transient hepatosplenomegaly, cytopenias, and progressive central nervous system involvement (coma, status epilepticus, and hydrocephalus). Despite normal initial cranial computed tomographic scan, diffuse swelling of the cerebellum with downward tonsillar herniation ensued. Diagnosis of hemophagocytic lymphohistiocytosis was difficult and delayed because of the relapsing course, and complete diagnostic criteria were not fulfilled at initial presentation. Central nervous system disease preceded the typical clinical picture of this disease; it dominated the clinical course and caused life-threatening complications and sequelae. The patient improved after treatment, according to the hemophagocytic lymphohistiocytosis protocol (HLH-94) of the Histiocyte Society, with dexamethasone, etoposide, and cyclosporine and unrelated cord blood stem cell transplantation. A mutation in the perforin gene confirmed the diagnosis of familial hemophagocytic lymphohistiocytosis.