Combined immunodeficiency presenting as the Letterer-Siwe syndrome.

Four infants with skin rash, hepatosplenomegaly, lymphocytosis, eosinophilis, and histiocytic infiltration of the lymph nodes and skin are described; in each of these infants an initial diagnosis of the Letterer-Siwe syndrome was made. Postmortem findings of thymic dysplasia and poorly differentiated, lymphopenic peripheral lympoid tissue in each of the four infants, as well as antimortem clinical findings in one, established a diagnosis of severe combined immunodeficiency. From these and similar cases in the literature, we postulate that the Letterer-Siwe syndrome may not be an unusual presentation of combined immunodeficiency. Appropriate immunologic studies will help to differentiate the two disorders.