ADENOMATOUS POLYPOSIS-COLI AND A CYTOGENETIC DELETION OF CHROMOSOME-5RESULTING FROM A MATERNAL INTRACHROMOSOMAL INSERTION

We present the clinical and laboratory findings in an institutionalise d adult patient originally referred for autism. A high risk of colorec tal cancer was predicted when an interstitial deletion of the long arm of chromosome 5, del(5)(q15q22.3), was detected in her lymphocytes an d deletion of the MCC and APC genes confirmed by molecular analysis. A denomatous polyposis coli and carcinoma of the rectum were subsequentl y diagnosed in the patient. She was profoundly mentally retarded, auti stic, and had minor dysmorphic features consistent with those of previ ous patients with similar deletions. The deletion arose as a result of recombination within the small insertion loop formed at meiosis by th e direct insertion (dir ins(5)(q22.3q14.2q15)) found in the patient's mother. This family further confirms the cytogenetic mapping of both M CC and APC genes to 5q22 and comparison with other recent cases sugges ts that both genes and their closely linked markers lie within the 5q2 2.1 subband.