del(15)(q13.3q13.3)

Epidemiology and Etiology:

· 0.3% of idiopathic MR

·

Common sites:

·

Gross features:

· Variable, nonspecific dysmorphic features

· Dysmorphic facies

· Hypertelorism

· Upslanting palpebral fissures

· Short and thick / prominent philtrum

· Full and everted lower lip

· Shortened fourth metacarpals

· 5^th finger brachydactyly/clinodactyly

· Growth parameters variable

Histologic features:

·

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Molecular features:

· 1.5 Mb deletion usually

· Between BP4 and BP5 seg dups

· BUT the homologous regions are inverted

· Therefore it may be an inversion polymorphism that predisposes to the deletion

· Present in 7 of 16 HapMap individuals of diverse ethnicities

· Found in both of the 2 available parents examined in the 15q13.3 deletion cases

· Reciprocal BP4-BP5 duplication has been observed

· CHRNA7 gene is a clear candidate for epilepsy

· Cholinergic receptor, neuronal nicotinic, alpha polypeptide 7

· Synaptic ion channel protein

Other features:

· DD (mild to moderate) +/- MR

· Seizures (variable in severity) (7 of 9 patients)

· Myoclonic

· Absence

· Grand mal

References:

· Slavotinek AM. Novel microdeletion syndromes detected by chromosome microarrays. Hum. Genet. 2008;124(1):1-17.