Disseminated langerhans cell histiocytosis-related sudden unexpected death in infancy.

Sudden unexpected death in infancy (SUDI) is defined as the sudden and unexpected death of an infant aged less than 1 year and comprises a heterogeneous group of deaths; in around one-third of cases a definite cause of death is identified at autopsy, while almost two-thirds of such deaths will remain unexplained despite a careful review of the circumstances of death and a detailed postmortem examination. We report a case of SUDI due to previously undiagnosed disseminated Langerhans cell histiocytosis (LCH) in a 10-month-old male, a disease characterized by a clonal proliferation of dendritic Langerhans cells. The diagnosis was established on histological examination, which revealed extensive infiltration by LCH of the skin, lymph nodes, thymus, spleen, and lungs. Despite a high mortality in disseminated disease, to our knowledge, this is the first reported case in the English-language literature of disseminated multisystem Langerhans cell disease presenting as SUDI. Furthermore, this case demonstrates the importance of routine microscopic tissue sampling in all SUDI, as the diagnosis required histological examination of the organs and might have been missed had histology not been performed.