Molecular characterisation of a ring chromosome 22 in a patient with severe language delay: a contribution to the refinement of the subtelomeric 22q deletion syndrome.

The common clinical features reported in ring chromosome 22 cases include overall developmental delay with severe speech disability, growth retardation with frequently associated microcephaly, hypotonia, and dysmorphic traits, such as epicanthus, normally placed but large and dysplastic ears, long eyelashes with full eyebrows, and occasionally high arched palate, dental malocclusion, and mild hypertelorism. Second and third toe syndactyly, unsteady gait, hyperactivity, aggressive behaviour, autistic disorders, 4 and seizures or abnormal EEG 2 have also been reported. The recently described subtelomeric 22q deletion syndrome showed overlapping clinical features with a generalised developmental delay, particularly severe in the area of expressive speech. The phenotype is usually more severe in cases of ring chromosome 22 compared with subtelomeric 22q deletions. The phenotypic differences, particularly the growth retardation with microcephaly and the severe mental delay, could be the result of a larger deletion size in ring chromosome 22 cases. We report the molecular cytogenetic analysis of a ring chromosome 22 in a young boy investigated for global development and severe speech delay. This is the first molecular analysis of a ring chromosome 22 harbouring the second smallest 22qter microdeletion reported so far. Characteristics of cases with ring chromosome 22 and subtelomeric 22q deletion are reviewed.