Clinical characterization of familial 1p36.3 microduplication.

Unlike the 1p36 microdeletion syndrome, which has been extensively described, 1p36.3 microduplications have rarely been reported. We report the two siblings of familial 1p36.3 microduplication, presenting with a severe global developmental delay, epilepsy, and a few dysmorphic features. They were referred to moderate-to-severe developmental delay (DD) and intellectual disability (ID). Both were considered eyelid myoclonus with absence of epilepsy (Jeavons syndrome). The EEG is characterized by widespread 2.5-3.5 Hz spikes and spike slow complex wave, eye closure sensitivity, and photosensitivity. The children has same dysmorphic features, including mild bitemporal narrowing and sloping forehead, sparse eyebrows, hypertelorism, ptosis, strabismus, infraorbital creases, wide nasal bridge with bulbous nasal tip, dystaxia, hallux valgus, and flat feet. Family exome sequencing revealed a maternally inherited 3.2-Mb microduplication of chromosomal band 1p36.3p36.2. However, DNA purified from blood samples of either parent did not find evidence for a microduplication of 1p36 in somatic tissue, indicating that such a mutation might be carried in the germline of the parents as gonadal mosaicism. No other family members of the affected siblings' parents were reported to be affected by the symptoms found.