The 22q13 deletion syndrome known as Phelan-McDermid is a neurodevelopmental disorder characterized by intellectual disability, hypotonia, delayed or absent speech, and autistic features. Research on the syndrome to date has focused on the SHANK3 deficiency phenotype, described in multiple case studies.

Scientists at the Mount Sinai Icahn School of Medicine this week present a first-of-its-kind prospective clinical study assessing patients with SHANK3 deficiency in an effort to paint a more complete picture of Phelan-McDermid syndrome.

Alex Kolevzon, M.D., and his colleagues studied 32 patients with SHANK3 deficiency, finding 22q13.3 deletions ranging in size from 101 kb to 8.45 Mb. Two patients showed de novo SHANK3 mutations. Writing in Molecular Autism, Dr. Kolevzon et al., also report high rates of autism spectrum disorder within the group studied—27 patients (84%) met the criteria. Seventy-seven percent of patients exhibited severe to profound intellectual disability and only five (19%) used some words spontaneously to communicate, the researchers added.

Further, in their genotype-phenotype analysis, the researchers found that “larger deletions were associated with increased levels of dysmorphic features, medical comorbidities, and social communication impairments related to autism.”

They add that their clinical, genomic evaluation of Phelan-McDermid syndrome could help guide future research and medical care.

“There is no established standard for assessing this type of autism, and our study provides important guidance in developing such a standard,” Dr. Kolevzon said in a statement.

“Knowing how large the deletion of the SHANK3 gene is may have important implications for medical monitoring and individualizing treatment plans,” he added, noting that his team’s “results also provide much-needed guidance in developing a standardized methodology for evaluating the features of this disorder.”

“Prospective investigation of autism and genotype-phenotype correlations in 22q13 deletion syndrome and SHANK3 deficiency” appeared online in Molecular Autism June 11.

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