Indeterminant Cell Histiocytosis in a Patient With Hemophagocytic Lymphohistiocytosis

Indeterminant cell histiocytosis is a rare disorder, which often presents as a benign, papular eruption without age or sex predilection. It is diagnosed based on histologic findings that are similar to those seen in Langerhans cell histiocytosis without the characteristic Birbeck granules. Hemophagocytic lymphohistiocytosis is a potentially life-threatening disease of immune overactivation that may present with severe symptoms and multiorgan involvement. It can develop because of a primary genetic mutation or secondary to a trigger. Despite their widely different clinical manifestations, both diseases originate from the monocyte-macrophage cell lineage. In this article, we describe the unique case of a 2-year-old patient presenting with both of these histiocytic pathologies.