Myeloproliferative disease in two young siblings.
Two siblings developed a myeloproliferative disease. One of them was a 9-year-old girl with a short history of bleeding, whose initial clinical and hematologic features were concordant with idiopathic myelofibrosis. Shortly afterwards this disorder evolved to a leukemic phase which subsequently resulted in the death of the patient. Four years later, at the age of 16, her brother was diagnosed as having acute myelofibrosis, and some months afterwards he died from fulminant pneumonia coincidently with pancytopenia and presence of scarce blast cells in peripheral blood. From the pathogenetic point of view, neither exposure to bone marrow toxins nor bone marrow chromosome abnormalities could be detected. HLA-typing disclosed the same haplotype (A2, A9, B5, B21, C5) in both patients.