Clinical characterization of novel chromosome 22q13 microdeletions

The advent of chromosome microarray analysis (CMA) for evaluation of patients with multiple congenital anomalies has made it possible to define chromosomal imbalances with greater precision and resolutions significantly smaller than possible by standard G-banded chromosome analysis. We describe two patients with novel chromosomal anomalies involving chromosome 22q13, a locus also associated with Phelan-McDermid syndrome (PMS).

We aim to characterize the novel phenotypic and genotypic findings of two patients with 22q13 microdeletions, distinct from PMS, comparing and contrasting with features of PMS.

Case 1 is a 4-year-old boy with global developmental delay, esotropia, moderate aortic root dilation, genu valgum, and in-toeing gait. MRI brain for evaluation of neonatal hypotonia revealed a left cerebellopontine angle arachnoid cyst. He referred on newborn hearing screening, and diagnostic auditory brainstem response (ABR) showed left profound retrocochlear hearing loss. Surgical intervention for the arachnoid cyst was deferred, with spontaneous resolution at age two years without hearing recovery. CMA revealed a novel, de novo 5.1 Mb microdeletion of 22q13.31q13.33 not involving SHANK3, a gene typically deleted in PMS. Case 2 is a 6-year-old girl with some features also seen in patients with PMS but also several atypical features. She has a complex chromosomal rearrangement including a 5.3 Mb 22q13 microdeletion (not including SHANK3) and de novo 2.1 Mb gain of 22q11.

As diagnostic sensitivity improves, smaller chromosomal imbalances will be detectable related to milder or different phenotypes. We present two patients with novel deletions of chromosome 22q13 associated with multiple congenital anomalies and features distinct from PMS.