Proteus syndrome caused by novel somatic AKT1 duplication.

Proteus syndrome (PS) is a rare overgrowth disorder that presents with asymmetrical growth of the bone and fat tissues following a mosaic pattern mutation. The estimated worldwide incidence is approximately one in one million live births. Proteus syndrome causes disfigurement and psychological impact through its effects on somatic tissue. Due to its rarity and diversity of tissues involved, it represents a significant challenge to caregivers and multidisciplinary medical teams. Here, we report a Saudi girl, with a large left cervical mass discovered antenatally. This mass was identified as a growing cystic hygroma, and she had features of overgrowth and hemangiomas. Whole exome sequencing was negative from the blood lymphocytes and affected tissue sample.  However, deletion duplication analysis from tissue shows a novel mosaic somatic mutation of the AKT1 gene. Somatic mutation remains an obstacle, and the geneticist has an essential role in its management, providing an established genetic diagnosis, prognosis, and family counselling.

Identification of TMC1 as a relatively common cause for nonsyndromic hearing loss in the Saudi population.

Hearing loss (HL) is the most common sensory disorder worldwide and genetic factors contribute to approximately half of congenital HL cases. HL is subject to extensive genetic heterogeneity, rendering molecular diagnosis difficult. Mutations of the transmembrane channel-like 1 (TMC1) gene cause hearing defects in humans and mice. The precise function of TMC1 protein in the inner ear is unknown, although it is predicted to be involved in functional maturation of cochlear hair cells. TMC1 mutations result in autosomal recessive (DFNB7/11) and sometimes dominant (DFNA36) nonsyndromic HL. Mutations in TMC1 are responsible for a significant portion of HL, particularly in consanguineous populations. To evaluate the importance of TMC1 mutations in the Saudi population, we used a combination of autozygome-guided candidate gene mutation analysis and targeted next generation sequencing in 366 families with HL previously shown to lack mutations in GJB2. We identified 12 families that carried five causative TMC1 mutations; including three novel (c.362+3A > G; c.758C > T [p.Ser253Phe]; c.1396_1398delACC [p.Asn466del]) and two reported mutations (c.100C > T [p.Arg34Ter]; c.1714G > A [p.Asp572Asn]). Each of the identified recessive mutation was classified as severe, by both age of onset and severity of HL. Similarly, consistent with the previously reported dominant variant p.Asp572Asn, the HL phenotype was progressive. Eight families in our cohort were found to share the pathogenic p.Arg34Ter mutation and linkage disequilibrium was observed between p.Arg34Ter and SNPs investigated. Our results indicate that TMC1 mutations account for about 3.3% (12/366) of Saudi HL cases and that the recurrent TMC1 mutation p.Arg34Ter is likely to be a founder mutation.