Abstract
A medical genetic study was undertaken of a large segment of an inbred Dutch kindred containing more than 2000 members. Noteworthy are occurrences of several hereditary precancerous diseases among the family members. These include two siblings with xeroderma pigmentosum and two siblings from another sibship who manifest a syndrome which may possible be a variant of Fanconi's aplastic anemia. Four patients had histologically verified testicular malignant neoplasms. Other generally rarely occurring cancers included Wilms' tumor, thymic carcinoma, and astrocytoma. At present there is no satisfactory etiologic explanation for these events in this family. Environmental factors common to the family cannot be excluded. Hereditary factors conditioned strongly by consanguinity may be operating in concert with as yet unknown nongenetic factors such as an oncogenic virus.