The ring 14 syndrome.

The ring 14 syndrome is a rare condition, whose precise clinical and genetic characterization is still limited. This review summarizes literature data and it describes our own experience with 27 patients with ring 14 syndrome. Clinically, the ring 14 syndrome is characterized by a recognizable phenotype of shortness of stature, distinctive facial appearance, microcephaly, scoliosis, and ocular abnormalities, consisting mainly of abnormal retinal pigmentation, but also retinitis pigmentosa, strabismus, glaucoma, and abnormal macula. Virtually all patients are intellectually delayed, with aggressive and hyperactive behavior in some. Drug-resistant, mainly focal in type, epilepsy is another highly consistent finding. In our own sample of patients the ring was complete, with no apparent loss of chromosome material, in 6/27 cases, while it showed a small terminal deletion, varying in size from 0.3 to 5 Mb, in the other 21. In two of these a cryptic 14q duplication of 2.5 and 9.7 Mb, respectively, proximal to the deleted segment, was also identified. Deleted rings were 75% paternal and 25% maternal in origin. UPD (14) was excluded in all cases. Based on literature review of linear deletions, affecting either the proximal or the distal 14q region, we could deduce that retinal abnormalities and epilepsy map within the proximal 14q11.2- q12 region. Because this region is preserved in all patients with ring 14, we speculate that genes residing in the proximal 14q interval are disregulated through heterochromatinization spreading from the adjacent short arm of the chromosome. Behavior disorders and susceptibility to infections can be assigned to the 14q32 region, haploinsufficiency being the most likely underlying mechanism.