Case report: an unexpected link between partial deletion of the SHANK3 gene and Heller's dementia infantilis, a rare subtype of autism spectrum disorder

Background: Deletions and mutations involving the SHANK3 gene lead to a nonspecific clinical presentation with moderate to profound intellectual disability, severely delayed or absent speech, and autism spectrum disorders (ASD). Better knowledge of the clinical spectrum of SHANK3 haploinsufficiency is useful to facilitate clinical care monitoring and to guide molecular diagnosis, essential for genetic counselling. Case presentation: Here, we report a detailed clinical description of a 10-year-old girl carrying a pathogenic interstitial 22q13.3 deletion encompassing only the first 17 exons of SHANK3. The clinical features displayed by the girl strongly suggested the diagnosis of dementia infantilis, described by Heller in 1908, also known as childhood disintegrative disorder. Conclusion: Our present case confirms several observations according to which regression may be part of the clinical phenotype of SHANK3 haploinsufficiency. Therefore, we think it is crucial to look for mutations in the gene SHANK3 in patients diagnosed for childhood disintegrative disorder or any developmental disorder with a regressive pattern involving social and communicative skills as well as cognitive and instinctual functions, with onset around 3 years.