Long-term treatment with insulin-like growth factor-1 in Phelan-McDermid syndrome: a case report

Phelan-McDermid syndrome (PMS) is a chromosomal microdeletion syndrome generally caused by loss-of-function variants or deletions affecting the SHANK3 gene. We report on a case of a 19-year-old woman with a diagnosis of PMS, autism, and developmental disability. She has been under clinical care since the age of 9 and received treatment with subcutaneous IGF-1 from 11 to 15 years of age. The treatment spanned 2 periods, totaling 35 months, interspersed with a 16-month off-treatment interval. Clinically significant improvement was evident during the treatment periods, particularly in the Social Responsiveness Scale, the Aberrant Behavior Checklist, and clinical assessments, contrasted with a clear deterioration during the off-treatment period. Sleep difficulties worsened during the first period, and EKG repolarization abnormalities emerged during the second period, ultimately leading to definitive treatment discontinuation. In conclusion, an experimental long-term on-off-on treatment with IGF-1 in an adolescent with PMS resulted in mixed results, showcasing positive clinical improvements alongside potentially severe adverse events in the long run.