SC phocomelia syndrome, premature centromere separation, and congenital cranial nerve paralysis in two sisters, one with malignant melanoma.

Two middle age sisters had most manifestations of the SC phocomelia syndrome including postnatal growth retardation, symmetric limb deficiencies with radial aplasia and absent thumbs, facial anomalies with microcephaly, microphthalmia, hypoplastic nasal alae, and borderline to mild mental retardation. Unusual findings included congenital paralysis of some cranial nerves in both patients and malignant melanoma in the proposita. Cultured lymphocytes from both patients, and skin fibroblasts, Epstein Barr virus-transformed lymphocytes, and tumor cells from the proposita demonstrated premature separation of centromeric heterochromatin (PCS) of many chromosomes, a finding noted previously in the SC phocomelia syndrome and the similar but more severe Roberts syndrome. Extensive overlap of the phenotypes of the sisters and 15 other patients with either syndrome and PCS confirms that these are either allelic conditions or the same disease--designated Roberts-SC phocomelia syndrome. The role of PCS in the syndrome(s) remains uncertain since some patients with the characteristic clinical phenotypes are reported to lack it.