PHELAN MCDERMID SYNDROME: A POTENTIAL UNDERLYING CAUSE OF UNEXPLAINED MENTAL RETARDATION IN THE PEDIATRIC POPULATION

Date

2013-04-12

Authors

Pickard, Brenna

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Abstract

Purpose: This case report will present information on a rare chromosome 22q13.3 deletion syndrome named Phelan McDermid syndrome(PMDS). With approximately 600 reported cases worldwide and minimal research published,physicians know little about this disorder.The diagnosis of PMDS is rarely diagnosed due to the broad array of presenting characteristics such as neonatal hypotonia, severely delayed speech,dysmorphic features,and global developmental delays.Because the subtelomeric fluorescence-in-situ hybridization(FISH)analysis used to detect the microdeletion is fairly new and the 22q13.3 deletion can go undetected on routine cytogenetic analyses,physicians remain uncertain on how to correctly diagnose these patients.This case report aims to educate others on the phenotypic and behavioral characteristics,genetic testing,and treatment for PMDS,as well as explain the importance of a gene involved named SHANK3.The loss of this gene produces the neurological aspects seen in PMDS,so this report will discuss how this syndrome could be a major underlying cause of unexplained mental retardation(MR)in the pediatric population. Methods: One representative case will be reviewed in detail with the approval of the patient's mother and pediatrician.We will review published literature to describe the clinical features of this syndrome and discuss genetic testing used for diagnosis. Results: Upon reviewing the patient's records,we identified features and comorbidities consistent with the reviewed literature. Due to the 22q13.3 deletion in PMDS,a gene named SHANK3 is lost.Shank proteins play a role in forming nerve connections and are crucial in brain cell communication;therefore,deletions of these genes cause a majority of the symptoms seen.Literature states SHANK3 mutations are found in other disorders which raise the possibility that PMDS is related to other diseases seen today such as schizophrenia and autism. Conclusions: PMDS is an infrequently recognized disorder that has not been extensively studied. Because of the difficulties in detecting this disorder, 22q13.3 deletions may go unnoticed, leading instead to the diagnosis of other MR spectrum disorders. With the presented information, physicians may gain a better understanding of how SHANK3 deletions link PMDS to other disorders and cause it to be a possible cause of unexplained MR.This case report also aims to raise awareness of this disorder so earlier detection may be possible and genetic counseling may be enhanced and utilized more frequently.

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