Familial polyposis of the colon

Summary Karyotypes in leukocytes in peripheral blood were normal in seven of eight patients with familial polyposis of the colon, with or without extracolonic manifestations. The eighth patient in the study had an XXY abnormality and Klinefelter’s syndrome. This finding of an XXY male with familial polyposis is probably a chance occurrence and not related to the familial polyposis of the colon. The extra chromosome did not appear to alter the clinical findings of familial polyposis, the free urinary amino-acid excretion, or the urinary polarographic findings in this patient, relative to the findings in a brother with polyposis and a normal karyotype. The grandfather of the patient with familial polyposis and Klinefelter’s syndrome apparently had developed the genotype as a spontaneous mutation.