The purpose of this study is to pilot the use of Insulin-Like Growth Factor-1 (IGF-1) treatment in 22q13 Deletion Syndrome (Phelan-McDermid Syndrome) caused by SHANK3 gene deficiency in order to evaluate safety, tolerability, and efficacy. IGF-1 is an injection under the skin that contains human IGF-1. IGF-1 is approved by the FDA under the brand name Increlex for the treatment of children with short stature due to primary IGF-1 deficiency. It is being used off-label in the current study and is not FDA approved, nor has it yet been studied in humans for the treatment of SHANK3 deficiency.