A nine-month-old-boy with Atypical Hemophagocytic Lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammation caused by uncontrolled proliferation of activated lymphocytes and histiocytes. Often, HLH is an acquired syndrome. We report a case of a nine month-old-boy presented with hepatosplenomegaly, severe anemia, thrombocytopenia, hypertriglyceridemia and high hyperferritinemia. These clinical features of HLH prompted a wide range of infectious and auto-immune tests to be performed. After an extensive diagnostic workup, he was referred to the immune-hematologic unit for HLH suspicion with an unknown cause. Primary HLH due to familial lymphohistiocytosis (FLH) was first evoked in front of consanguinity, probable HLH in the family, early onset, and in the absence of a causative pathology like infection or cancer. However, functional tests were normal. Atypical features like the: absence of fever, hypotonia, recurrent diarrhea since diversification, hematuria, and proteinuria suggested an inborn metabolism error with gastrointestinal involvement. Specific tests were performed to reach a final diagnosis.