Retinal and optic nerve abnormalities in neurodegeneration associated with mutations in C19orf12 (MPAN)

Mitochondrial membrane protein-associated neurodegeneration (MPAN) is an neurodegeneration with brain iron accumulation (NBIA) subtype with mutation of C19orf12. Optic atrophy is one of the core symptoms in almost all MPAN cases, but the detailed ophthalmologic features of MPAN patients have not yet been described.

All consecutive symptomatic, gene proven MPAN patients underwent a detailed ophthalmological examination: best corrected visual acuity (BCVA), slit lamp examination, dilated fundus examination, tonometry, optical coherent tomography (OCT) and electrophysiological examinations. The total thickness of the macula (Mth) and the retinal nerve fiber layer (RNFL) were measured separately.

Six males aged 18 to 21years were examined. Dilated fundus examination revealed complete optic disc paleness in 5 patients. In all patients, the Mth was normal. The total RNFL was thin in five patients. The latencies of PVEP were prolonged in all patients except one. In all cases, the ERG latencies and amplitudes were normal under both scotopic and photopic conditions. One patient, carrying different mutation and with different disease course, had a normal optic nerve head, normal RNFL thickness and PVEP latencies.

Optic nerve atrophy seems to be genotype-dependent in MPAN patients but is typical for the disease. This phenomenon, together with normal ERG examination, is most distinctive for MPAN.