A novel mutation and novel features in Nijmegen breakage syndrome

Editor—Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder, characterised by microcephaly, bird-like face, growth retardation, immunodeficiency, cytogenetic abnormalities, increased radiosensitivity, and high susceptibility to lymphoid malignancy. The NBS1 gene, mapped on chromosome 8q211 and recently cloned,2 3codes for nibrin, a member of the hMre11/hRAD50 protein complex, involved in DNA double strand break repair. The NBS Registry in Nijmegen includes 55 patients. The majority of them are of eastern European origin and share a common haplotype, suggesting a founder effect, and a mutation consisting of a truncating 5 bp deletion in exon 6, 657-661 del ACAAA.4 Five further mutations have been found in six patients with different haplotypes and of various ethnic origins. We found a new mutation of the NBS1 gene in a 2 year old girl from Morocco. The patient, a girl born at term in August 1997 (fig 1), is the third child of apparently non-consanguineous parents; the two brothers, aged 12 and 6 years, are healthy. The pregnancy was uneventful until the 33rd week, when growth retardation, dilatation of the cerebral ventricles, and agenesis of the corpus callosum was diagnosed by ultrasound examination. Figure 1 (A) The patient at 18 months. (B) The right hand with preaxial polydactyly. Birth weight was 2520 g (3rd centile), length 46 cm (<3rd centile), and head circumference 28.5 cm (<3rd centile). Physical examination showed a “bird-like” face with strabismus, downward slanting palpebral fissures, large and low set dysmorphic ears, and a high palate. The hands showed right preaxial polydactyly and bilateral clinodactyly of the fifth finger with a short middle phalanx and single flexion crease. The feet showed bilateral cutaneous syndactyly 4-5. Severe gastro-oesophageal reflux was also present. Normal findings were obtained on ultrasound examination of the heart and abdominal structures including the ovaries. Agenesis …