Unique Case of Congenital Langerhans Cell Histiocytosis Presenting as Intrauterine Fetal Demise.

Congenital Langerhans cell histiocytosis (LCH) (formerly called Letterer-Siwe disease) is characterized by a clonal proliferation of Langerhans cells occurring in children at birth and manifests typically with multifocal cutaneous lesions, hepatosplenomegaly, lymphadenopathy, pulmonary lesions, and destructive osteolytic bone lesions. We present a case of LCH involving multiple systems high-risk organs (LCH MS-RO+), in a 32-week stillborn from a 20-year-old G2A1. The fetus was mildly hydropic and pale. Apart from maceration, the skin showed multiple targetoid lesions over the face, trunk, and limbs. There was hepatosplenomegaly and a pale brain. The placenta was large and bulky. Despite severe autolysis, histological examination showed disseminated histiocytes with multinucleated giant cells in the skin, lungs, thymus, mesenteric lymph nodes, spleen, and brain. By immunohistochemistry, the histiocytes were positive for S100, CD1a, and Langerin (CD207), confirming the diagnosis of LCH. There was extramedullary hematopoiesis in the spleen, brain, and placenta. Targeted next-generation sequencing performed on thymic DNA did not show the BRAF p.V600E variant but did show the MAP2K1 p.F53_Q58delinsL. Infants with LCH pose a diagnostic challenge due to their heterogeneous presentations. Our case is unusual in that the newborn presented with severe multiorgan involvement including brain and intrauterine death. LCH is still poorly understood requiring further genetic and molecular studies.