Predisposition to atypical teratoid/rhabdoid tumor due to an inherited INI1 mutation.

Germline mutations of the INI1 gene predispose children to the development of rhabdoid tumors. Reports of familial cases, however, are extremely rare. We have identified a three-generation family in which two half-brothers were diagnosed with central nervous system atypical teratoid/rhabdoid tumors (AT/RT). The two boys, diagnosed at 2 months and 17 months of age, had a germline insertion mutation in exon 4 of the INI1 gene that was inherited from their healthy mother. A maternal uncle died in childhood from a brain tumor and a malignant rhabdoid tumor of the kidney, and presumably carried the same germline mutation. As the mother and uncle had different fathers, the grandmother is also an obligate carrier of the mutation. The identification of two unaffected carriers in a family segregating a germline mutation and rhabdoid tumor supports the hypothesis that there may be variable risks of development of rhabdoid tumor in the context of a germline mutation. There may be a developmental window in which most rhabdoid tumors occur. This family highlights the importance of mutation analysis in all patients with a suspected rhabdoid tumor.