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JOYCE MBEKEANI, Hachemi Nezzar, Ola Al Ali, Zahra Al Sahlawi, Abdelmoneim Eldali, Mohammed Al Owain; OPTIC ATROPHY IN CLASSICAL METHYLMALONIC ACIDEMIA. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5553.
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© ARVO (1962-2015); The Authors (2016-present)
Methylmalonic acidemia (MMA) is an autosomal recessive disorder resulting in failure to process various amino acids and lipids. The classical form results in methylmalonyl CoA mutase deficiency, preventing the Vit B12-dependent conversion of methylmalonyl CoA to succinyl CoA, required in Krebs cycle. Patients typically present in early infancy with lethargy, vomiting, dehydration and failure to thrive. Long-term complications include renal failure (CRF), encephalopathy and pancreatitis. 4 cases of optic atrophy (OA) have been reported in classical MMA on appropriate dietary restrictions. The exact etiology is unknown but likely is multi-factorial. With improved survival of patients offered advanced treatment, OA needs to be identified so that prophylactic/therapeutic intervention, when available, can be incorporated into management protocols. The purpose of this observational study is to identify and determine the prevalence of OA in a small cohort of patients with classical MMA.
22 patients clinically diagnosed and genetically confirmed to have classical MMA were assessed with full history, neuroophthalmic exam, fundus photos and visual evoked potentials (VEP). Diagnosis of OA was determined by a combination of visual acuity, pupil reactions, optic nerve appearances, OCT and VEP. Associations of tabulated data were determined using Mann-Whitney U, Kruskal-Wallis, Chi-squared and Fisher’s exact tests.Statistical significance was set at p<0.05. Patients with proprionic acidemia and intracellular cobalamin metabolism disorders, which have clinical features of MMA were excluded.
8 patients were female and 14, male. Age range was 7 to 27yrs (median=14;IQR=11-16).13 patients (59%) had OA; 85% of these were bilateral. 6 (46.15%) reported decreased vision and 7 (53.85%) were asymptomatic.12 patients had CRF (median=16;IQR=14.5-20). Age was not significantly associated with OA (p=0.17) but significantly related to CRF (p=0.0067). Patients with OA were more likely to have CRF than those without OA (p=0.0058).
Optic atrophy is a frequent finding in classical MMA and most commonly is bilateral and sub-clinical. A positive correlation with CRF, known independently to be associated with OA, suggests a contributing causal relation. These findings have important clinical and management implications: early and periodic ophthalmic exams including VEP and OCT should be performed in all, including asymptomatic patients with MMA.
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