Phelan-McDermid syndrome. Chromosome 22q13 deletion syndrome.
Incidence
Seems to be a rare syndrome. Sporadic. Due to difficulties in detection, this chromosome deletion syndrome is under-diagnosed and its true incidence remains unknown.
Clinical Characteristics
The deletion 22q13 syndrome is a microdeletion syndrome characterized by neonatal hypotonia, global developmental delay, normal to accelerated growth, absent to severely delayed speech, and minor dysmorphic features. Facial features include dolicocephaly, full brow, ptosis, long eye lashes, wide nasal bridge, flat midface, puffy eyelids, full cheeks, bulbous nose, large or unusual ears, and pointed chin. Other features are large hands, dysplastic toenails, lack of perspiration, and sacral dimple. Behavior is described as "autistic-like" and includes high tolerance to pain and habitual chewing or mouthing. The loss of sub-band 22q13.3 on the long arm of chromosome 22 can be very subtle and is often undetected by routine chromosome analysis. Fluorescence in situ hybridization (FISH) is typically required to confirm the presence of this deletion. Over 30% of affected individuals have required two or more chromosome studies before the abnormality was detected. Due to difficulties in detection, this chromosome deletion syndrome is under-diagnosed and its true incidence remains unknown. No apparent life-threatening organic abnormalities accompany the diagnosis of deletion 22q13. Affected individuals benefit from early intervention programs, intense occupational and communication therapies, adaptive exercise and sports programs, and other therapies to strengthen their muscles and increase their communication skills.
Precipitants
None
Provocation Tests
None
Diagnostic Procedures
Karyotype. The loss of sub-band 22q13.3 on the long arm of chromosome 22 can be very subtle and is often undetected by routine chromosome analysis. Fluorescence in situ hybridization (FISH) is typically required to confirm the presence of this deletion. Over 30% of affected individuals have required two or more chromosome studies before the abnormality was detected. Due to difficulties in detection, this chromosome deletion syndrome is under-diagnosed and its true incidence remains unknown.