EPOS

European Paediatric Ophthalmological Society

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Heterogeneity of retinal degeneration in cobalamin C disease methylmalonic aciduria with homocystinuria.

Gaillard Marie-Claire, Matthieu Jean-Marie, Borruat Fran
¹H, ²Pediatric metabolic diseases unit, CHUV, Lausanne, Switzerland

Purpose:To report the incidence and characteristics of retinal lesions and ERG abnormalities in Cobalamin C methylmalonic aciduria with homocystinuria (Cblc disease), a rare autosomal recessive inborn error of cobalamin metabolism, characterised by neurological, haematological and ophthalmological abnormalities. Methods:Three consecutive patients with Cblc disease were examined under general anaesthesia. Investigations included slit lamp biomicroscopy, fundus examination and full-field ERG (ISCEV standards). Results:Retinopathy and abnormal full-field ERG were present in all three patients. Retinal lesions consisted of a maculopathy in two cases (mottled appearance, metallic reflex) and a salt and pepper retinopathy in the third patient. Photopic ERG was abnormal in one patient with salt and pepper retinopathy and both photopic and scotopic ERG were abnormal in the remaining two patients. Conclusion:Visual disturbance can be present in Cblc disease. Retinopathy has been reported in 27/68 cases. ERG was performed in only 7/68 cases and was abnormal in 5/7 cases, all with retinopathy. Despite early treatment (OH-Cbl and betain) and regular metabolic controls, all our patients exhibited both retinal and ERG abnormalities. There was no correlation between funduscopic appearance and the type of photoreceptor dysfunction. Retinal dysfunction in Cblc disease may be more frequent than previously thought, and can involve cones only or both rods and cones. Similarly the retinal appearance can vary from a maculopathy to a widespread retinopathy. We recommend that formal ocular examination and full-field ERG to be performed when assessing patients with Cblc disease.