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22q13.33 Microdeletion Syndrome

Name of disease:

22q13.33 Microdeletion Syndrome

ICD-10 diagnosis code:

Q93.5

Causes:

Most cases of Phelan-McDermid syndrome (PMS) are sporadic, which means they occur in people with no history of the disorder in their family. It is caused by the deletion of the end of chromosome 22 or mutation of SHANK3 gene. Deletion usually occurs during the formation of reproductive sperms or eggs or in early fetal development.

Mode of inheritance:

PMS cases can be sporadic or are inherited from parents in autosomal dominant pattern (20%).

Prevalence:

Unknown

Diagnosis:

The diagnosis of PMS is based on chromosomal microarray analysis/ molecular genetic testing to determine whether there is gene deletion or mutation in chromosome 22. It can also be confirmed through clinical evaluations and physical findings, and chromosomal microarray is the first tier of testing.

Age of onset:

Neonatal to early childhood

Common signs and symptoms:

Developmental delay Low or weak muscle tone Moderate intellectual disability Absent or delayed speech Autism Sleep disorder Problems with swallowing and eating Mild to severe seizur Reduced swea Low perception of pain Kidneyabnormalities

Available treatments (medicinal and non-medicinal):

At present, there is no treatment or cure for PMS, but we may address the symptoms of PMS, which requires coordinated efforts of different specialists.

Disease management tips:

The management of patients with PMS requires an experienced, multidisciplinary approach to tackle the signs and symptoms of PMS. Physical and occupational therapists are needed for the low and weak muscle tone of patients so that they can overcome the developmental delay. Speech or language therapists shall be consulted if the patients exhibit symptoms of autism and delayed or even absent speech. Caregivers shall give extra attention when patients are eating because they may face problems with swallowing and eating. Food can be specially prepared for them. Due to reduced sweat, they have a higher risk of overheating. Therefore, caregivers shall protect the individual from direct sunlight and keep them hydrated to prevent heatstroke. Due to low perception of pain and delayed or absent speech, patients may not be able to express their pain. Therefore, caregivers should pay attention to the injuries. Since around 25% of PMS patient may have kidney abnormalities, they should have a renal ultrasound to check for any kidney defects.

References:

https://rarediseases.org/rare-diseases/phelan-mcdemid-syndrome/ https://www.pmsf.org/about_pms/

Other useful websites:

More about the disease: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3366702/ Patient groups: Phelan-McDermid Syndrome Foundationhttps://www.pmsf.org