INPP5K-related muscular dystrophy caused by a novel synonymous splicing variant in a Chinese patient: a case report
Higher Education PressCongenital muscular dystrophies (CMDs) represent a genetically heterogeneous group of disorders characterized by muscle weakness, dystrophic changes on muscle biopsy, and onset typically in infancy or childhood. Variants in the INPP5K gene, which encodes a phosphoinositide 5-phosphatase that regulates phosphoinositide signaling, have recently been identified as a rare cause of congenital muscular dystrophy, commonly associated with early-onset cataracts and intellectual disability. This case report describes the first Chinese patient with INPP5K-related muscular dystrophy, a 28-year-old male with a notably mild phenotype that lacked intellectual disability, expanding the clinical spectrum of this disorder. The patient presented with bilateral cataracts requiring surgical correction at age 5, followed by adolescent-onset limb girdle weakness with postural hand tremors beginning at age 15 and progressive lower limb weakness at age 16. Muscle magnetic resonance imaging revealed a characteristic pattern of selective fatty infiltration, with severe involvement of gluteal and thigh muscles and striking sparing of the rectus femoris, sartorius, and gracilis muscles, a pattern that provides important diagnostic clues. Genetic analysis identified compound heterozygous novel INPP5K variants: a missense variant c.274C>T, p.(Arg92Cys), and a synonymous variant c.261G>A, p.(Lys87=).
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