| An extremely rare genetic disorder characterized by monocytosis, autoimmune cytopenias, lymphoproliferation, hepatosplenomegaly, and hypergammaglobulinemia. Age of onset of the clinical signs is invariably in infancy or early childhood. Most patients have atypical features such as elevated counts for cells of myeloid origin (monocytosis and granulocytosis) making their clinical presentation indistinguishable from juvenile myelomonocytic leukemia. Caused by somatic mutations in the NRAS (1p13.2) and KRAS (12p12.1) genes encoding RAS proteins involved in regulating cell proliferation causing impairment of the intrinsic apoptosis pathway. The pattern of inheritance is not known. RAS mutations are considered somatic and limited to the circulating peripheral blood mononuclear cells. |
