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Background: Congenital hyperinsulinism is a genetically heterogeneous disorder, but mutations in the components of the ATP-sensitive potassium channel K(ATP) account for more than a third of all isolated congenital hyperinsulinism cases. The association between congenital hyperinsulinism and rhabdomyolysis has not been reported., Objective: To describe significant skeletal muscle manifestations in a family with a novel mutation in KCNJ11 (encoding the Kir6.2 component of K(ATP))., Methods: Cross-sectional analysis of members of a large multiplex consanguineous family with congenital hyperinsulinism and rhabdomyolysis using autozygosity mapping and exome sequencing., Results: Five affected members of an extended consanguineous Saudi family were recruited along with relevant unaffected relatives. We were able to map an apparently novel syndrome of congenital hyperinsulinism and severe rhabdomyolysis leading to acute renal failure to a single locus that harbours KCNJ11 in which we identified a novel homozygous mutation., Conclusions: This study expands the phenotype associated with KCNJ11 loss of function in humans and calls for increased awareness of rhabdomyolysis as a potential late-onset life-threatening complication of KCNJ11-related congenital hyperinsulinism.

One of us recently described an apparently novel ocular syndrome characterized by microcornea, myopic chorioretinal atrophy, and telecanthus (MMCAT) in a number of Saudi families. Consistent with the presumed pseudodominant inheritance in one of the original families, we show that MMCAT maps to a single autozygous locus on chr16q23.1 in which exome sequencing revealed a homozygous missense change in ADAMTS18. Direct sequencing of this gene in four additional probands with the same phenotype revealed three additional homozygous changes in ADAMTS18 including two nonsense mutations. Reassuringly, the autozygomes of all probands overlap on the same chr16q23.1 locus, further supporting the positional mapping of MMCAT to ADAMTS18. ADAMTS18 encodes a member of a family of metalloproteinases that are known for their role in extracellular matrix remodeling, and previous work has shown a strong expression of Adamts18 in the developing eye. Our data suggest that ADAMTS18 plays an essential role in early eye development and that mutations therein cause a distinct eye phenotype that is mainly characterized by microcornea and myopia., (© 2013 WILEY PERIODICALS, INC.)