Chromosome 20 deletion in human multiple endocrine neoplasia types 2A and 2B: a double-blind study.

Multiple endocrine neoplasia type 2A and 2B (MEN-2A and MEN-2B) are autosomal dominantly inherited syndromes in which medullary thyroid cancers are associated with adrenal pheochromocytomas. A double-blind analysis of high-resolution G-banded chromosomes was performed on blood specimens from patients in four MEN-2A families and five MEN-2B (mucosal neuroma phenotype) families and from control subjects. Excluding studies on duplicate blood specimens, 9 of 11 control subjects were scored as having normal chromosomes 20, and 11 of 14 MEN-2 patients were scored as having chromosomal deletion: del(20)(p12.2p12.2) (phi 2 = 9.00; P less than 0.001). Two new mutant MEN-2B patients had apparently normal chromosomes 20. These findings demonstrate that the dominant mutation in most MEN-2A and MEN-2B families is a visible chromosome deletion within band 20p12.2.