X-linked dyskeratosis congenita with pancytopenia.

Two maternal male cousins in a Jewish Iraqi kindred were affected with dyskeratosis congenita and had a megaloblastic bone marrow. One cousin had pancytopenia and the other had thrombocytopenia. The kindred displays a deficiency of glucose-6-phosphate dehydrogenase (G6PD) and a beta-thalassemia trait. The following genetic "markers" of the X chromosome were studied: G6PD, the X-linked blood groups Xg, and color vision. Linkage analysis indicated that dyskeratosis, G6PD, and Xg are far apart on the X chromosome. Chromosomal studies showed a 46XY karyotype in both cases; however, nonspecific numerical aberrations and structural abnormalities were found in the first and in the second case, polyploidy was seen in four of 60 cells. The proband's cultured fibroblasts did not show increased susceptibility to malignant transformation by simian virus 40, an oncogenic virus.