The 13q-deletion syndrome.

Abstract

Clinical data are available for 23 cases with the karyotype 46 Dqor 46 Dr. Seventeen cases have been published, data on four were obtained through personal communication, and two have been studied in our laboratory. Autoradiographic identification of a ring D chromosome has previously been made in six of these cases. In five, the ring originated from a chromosome 13 (Bloom et al 1967; Gerald et al. 1967; Hollowell et al. 1967; Niebuhr and Mikkelsen, personal communication [1968]; and Stimson and Hecht, personal communication [1968]). In one case (Sparkes et al. 1967), the ring apparently originated from a chromosome 14. The authors postulated that their case represented a unique syndrome characterized by absent thumbs and suggested that the same syndrome was present in two cases reported earlier, each having an unidentified ring D chromosome (Bain and Gauld 1963; Adams 1965). The patient studied by Sparkes et al. (1967) had microcephaly, hypertelorism, a broad nasal bridge, ocular dystrophy, and large ears. These features are characteristic of the Dr syndrome which Lejeune et al. (1968) proposed as antithetical to trisomy 13. Congenital anomalies typical of the Dr syndrome have also been observed in individuals with aDqchromosome.Three of these patients had hypoplastic thumbs (Thompson and Lyons 1965; Laurent et al. 1967; Hollowell, personal communication [1969]). The Dqchromosome originated from a chromosome 13 in two cases where terminal labeling studies were performed (Gey, personal communication [1968]; Hollowell, personal communication [1969]). The present paper concerns two clinically similar cases which resemble others with the karyotype 46 Dqor 46 Dr. Case 1 has a small deletion from a distal segment of the long arm of a D-group chromosome, and case 2 has a ring D chromosome. We have identified each abnormal chromosome autoradiographically as a chromosome 13. We postulate that our cases illustrate one distinct chromosome-deletion syndrome caused by partial monosomy for a distal segment of the long arm of chromosome 13.