Analphoid marker chromosome in a patient with hyper-IgE syndrome, autism, and mild mental retardation

Hyper-IgE syndrome with recurrent infections (HIES) is a primary immunodeficiency disease characterized by recurrent skin and lung abscesses and extreme elevations of serum IgE, but also involving dentition, bones, and connective tissue. Although the etiology of HIES is unknown, autosomal dominant inheritance has been observed in multiple kindreds. A 17 year old male with sporadic HIES, autism, and mild mental retardation was found to have a supernumerary marker chromosome in peripheral blood lymphocytes and skin fibroblasts. Microdissection and FISH analysis of the marker chromosome showed that it was derived from a small interstitial deletion of one homologue of chromosome 4q21. Lack of hybridization of probes specific for telomeres and alphoid centromeres, including a centromere 4 specific probe, established that the marker was an analphoid ring chromosome. Comparative genotyping of transformed B-cell subclones with (M+) and without (M–) the marker chromosome showed loss of the maternal alleles in M– cells between markers D4S1569 and D4S3010. FISH using YAC clones from 4q21 confirmed the size and location of the interstitial deletion. Thus our patient’s phenotypes were associated with de novo formation of a marker chromosome containing 15–20 cM of DNA deleted from his maternally derived chromosome 4. Proximal chromosome 4q therefore is a candidate region for disease genes for both HIES and autism. Identification of genes disrupted or lost during the formation of the marker chromosome as well as linkage studies in kindreds with HIES or autism may help us to understand the etiology of these complex phenotypes.