Purpose: To document a distinct vitreo-retinal dystrophy with early-onset cataract as related to recessive KCNJ13 mutations.
Methods: A retrospective case series (two patients from two families) Results: A 12-year-old Saudi Arabian girl with nystagmus since birth was referred because of recent decreased vision. Parents were first cousins and a younger sister had been diagnosed with retinal dystrophy. Examination revealed total white cataract in the right eye. In the left eye, there were posterior cortical lenticular opacities and an unusual retina fundus dystrophic appearance notable for fibrosis over the optic disc and clumped pigmentation. After right eye cataract surgery, the posterior pole of the left eye was seen as similar to that of the right eye and electroretinography revealed severe cone-rod dysfunction, with only subnormal scotopic tracings recordable in both eyes. Next-generation sequencing of retinal dystrophy genes revealed homozygosity for a novel missense mutation in KCNJ13 (c.359T > C; p.Ile120Thr [NM_002242.4]), which co-segregated with the disease. Direct KCNJ13 sequencing for an unrelated 33-year-old Saudi Arabian male with similar clinical findings but early-adult-onset rather than juvenile cataract revealed the same homozygous mutation.
Conclusions: Juvenile or early-adult-onset cataract in the setting of a congenital vitreo-retinal dystrophy notable for fibrosis over the disc and clumped pigmentation in the posterior pole is a unique phenotype that suggests recessive KCNJ13 mutations.
Keywords: Juvenile cataract; KCNJ13; retinal dystrophy.