[MIM 606 232]

(deletion 22q13, monosomy 22q13)

Unknown incidence, probably underestimated because the cytogenetic diagnosis is difficult to establish. Syndrome caused by the deletion of part of the terminal band of the long arm of one of the two chromosomes 22. It is usually an isolated and de novo mutation,  but it may be the result of an inherited translocation (10 %) or associated with a ring of the chromosome 22. The deletion causes a loss of the SHANKS3 or ProSAP2 gene coding for structural protein of the excitatory synapses, particularly in the cerebral cortex and the cerebellum. 

The syndrome combines, at variable degrees:

-        neonatal hypotonia, with feeding difficulties (it tends to improve with growth)

-        moderate to deep mental retardation: profond speech disorders and autistic features (75 %) (stereotyped movements such as  endless chewing behavior, poor eye contact); sometimes agressive behavior

-         psychomotor developmental delay

Height and weight development is sometimes accelerated. Dysmorphism is often present: dolichocephaly, ptosis with long eyelashes, epicanthus, prominent nose with a wide base, small pointed chin, wide or dysplastic ears. In addition, hands and feet are wide, and syndactyly of toes 2-3 may be present. There is a decreased ability to sweat. Epilepsy in 30 % of cases.

More rarely: renal (38 %) (agenesis, dysplasia, horseshoe kidney) and cardiac (25 %) (ASD, arteriosus ductus, abnormal pulmonary veous return) abnormalities, deafness, increased tolerance to pain (risk of self-injury).

RMI: arachnoid cysts, ventriculomegaly, anomalies of the corpus callosum  and myelinization disorders may be present

Anesthetic implications: 

renal and cardiac echography, autistic behavior; epilepsy; higher pain threshold ?; risk of hyperthermia; risk of aspiration.

References : 

-         Mc Phelan MC. Deletion 22q13 syndrome.
http://www.orpha.net/data/patho/GB/uk-22q13.pdf

-        Afenjar A, Burglen L.
Nouveaux syndrome microdélétionnels.
Médecine Thérapeutique Pédiatrie ; 2008 : 11 : 224-9.

-        Kolevzon A, Angavita B, Bush L, Wang AT et al.
Phelan-McDermid syndrome : a review of the literature and practice parameters for medical assessment and monitoring.
J Neurodev Disord 2014 ; 6 : 39, 12 p 

-        Kavakli AS, Sugur T, Metinyurt HF.
Anaesthesia and orphan disease: Phelan-McDermid syndrome.
Eur J Anaesthesiol 2020; 137: 730-1.

Updated: July 2020