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Tomas S Aleman, Lucas Bonafede, Monte D Mills, Brian J Forbes, Gil Binenbaum, Charles W Nichols, Stefanie L Davidson, Can H Ficicioglu, Bart Peter Leroy, Albert Maguire; Cobalamin C Deficiency Shows a Rapidly Progressing Maculopathy with Severe Ganglion Cell Loss. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3849.
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© ARVO (1962-2015); The Authors (2016-present)
To describe the retinal structure and function of a group of patients with cobalamin C (cbl C) disease.
Patients with cbl C disease underwent complete ophthalmic examinations, color and near-infrared retinal imaging as well as spectral domain optical coherence tomography (SD-OCT). Longitudinal data was available in most patients.
Results: Patients (n=11, age 6 months to 15 years) carried homozygous or compound heterozygote mutations in the methylmalonic aciduria and homocystinuria type C (MMACHC) gene. With the exception of one patient who had a normal retinal exam, all patients showed a maculopathy. Measurable visual acuities ranged from 20/200 to 20/400. Nystagmus was present in 8/11 patients. In general, retinal changes were first observed before one year of age and progressed within months to a well-established maculopathy. Wide-spread retinal degeneration was noted in older patients (n=4; >7 years of age). SD-OCT showed macular thinning, predominantly of the ganglion cell layer (GCL), accompanied by outer nuclear layer (ONL) loss. Inner retinal thickening was observed in areas of GCL/ONL loss. A normal lamination pattern in the peripapillary nasal retina was often seen despite severe central retinal disease. Large well-demarcated areas of foveal chrorioretinal atrophy with the appearance of pseudo-colobomas were documented in three patients.
This subset of patients with cbl C and MMACHC mutations showed an early-onset, unusually fast-progressing maculopathy. There was some indication that the severe GCL loss exceeded that expected for a primary photoreceptor disorder, pointing to the GCL as the primary site of disease. An abnormally thickened inner retina supports a remodeling response to degeneration and/or interference with normal development in this condition.
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