Retinitis pigmentosa and punctate cataracts in mevalonic aciduria.

Abstract

Mevalonic aciduria, caused by deficiency of mevalonate kinase, was the first recognized defect in the biosynthesis of cholesterol and isoprenoids. Ophthalmic features of this potentially blinding disorder include blue sclera, cataract, uveitis, optic atrophy, and, importantly, a retinitis pigmentosa-like retinopathy. To date, ∼30 cases of this rare autosomal recessive disorder have been reported, with no full characterization appearing in the ophthalmic literature. An 11-year-old white girl with mevalonic aciduria presented with decreasing peripheral vision and night blindness. Examination revealed decreased central vision, punctate cataracts, and a retinitis pigmentosa-like retinopathy. Goldmann visual fields confirmed severe constriction in both eyes. A full-field electroretinogram was performed. A-waves, B-waves, and oscillatory potentials were all nonrecordable in both eyes, indicating severe bilateral retinopathy, affecting both cone- and rod-mediated responses. Dark adaptation testing showed severely impaired cone and rod function under dark-adapted (scotopic) conditions. Farnsworth-Munsell hue discrimination (FM-100 hue) testing was abnormal in both eyes. The ocular findings in patients with mevalonic aciduria are heterogeneous and include blue sclerae, cataracts, uveitis, retinopathy, and optic atrophy. Visual prognosis is guarded; several patients surviving to adulthood have progressed to apparent legal blindness caused by cataracts and/or retinopathy.