Interstitial deletion of 13q associated with polymicrogyria.

Interstitial deletion of the long arm of chromosome 13 is a rare condition characterized by multiple clinical findings. We report a male dizygotic twin with an interstitial deletion of 13q and failure to thrive, hypotonia, polymicrogyria, bilateral foci of retinoblastoma, hearing loss, bilateral inguinal hernias, submucous cleft palate, and dysmorphic features including a triangular shaped face, broad forehead, small chin, prominent eyes, downslanting palpebral fissures, and a downturned mouth. Chromosome analysis showed an interstitial deletion of chromosome 13 which was confirmed by fluorescence in situ hybridization analysis to include the Rb locus, but spare the 13q subtelomeric region. The karyotype was 46,XY,del(13)(q14.1q31.2).ish del(13)(RB1-,D13S327+) de novo. Breakpoints were further characterized by SNP-based microarray. Retinoblastoma tumors are a well-known complication of deletion of the retinoblastoma susceptibility gene, located at chromosome 13q14.2. Growth retardation is another common feature that has been described in other patients with a deletion of 13q. Additionally, this patient had brain findings on MRI consistent with bilateral polymicrogyria with predominance of the frontal lobes, as well as prominent infratentorial and supratentorial vasculature. There are a variety of polymicrogyria syndromes that are distinguished by the cortical location of the abnormal folding. Several of the subtypes have known genetic loci associated with them. To our knowledge, this is the only report of polymicrogyria in association with a deletion of chromosome 13.