Conversion From Asymptomatic Carrier to Affected Status of Leber's Hereditary Optic Neuropathy (LHON)

Abstract

Abstract: : Purpose: To prospectively study a 300 member LHON pedigree with extensive clinical and psychophysical testing and document the changes as two LHON Carriers converted to Affected status. Methods: Since 2001 we have comprehensively evaluated and then systematically reexamined members of a very large family with 11778 LHON. Two asymptomatic Carriers were followed as they developed mild visual signs and then classical severe visual impairments associated with Affected LHON. These and the other Carriers had all undergone a formal and rigorous neuro–ophthalmic investigation including visual fields (HVF), and fundus photography. We also conducted sophisticated psychophysical examinations including Cambridge Research Systems color vision and contrast sensitivity testing, GDx, HRT, VERs and ERGs. Blood testing for mtDNA, and serial serum for oxidative stress and NSE were also performed. Results: Both subjects were asymptomatic when our investigations began. Both were males and 14 and 44 respectively. Despite their subjective claims of normal vision, they both demonstrated several subclinical impairments. These included peripapillary nerve fiber layer (NFL) swellings, especially at 6 o’clock, mild associated telangectasis, slight decrease in the papillomacular NFL thickness, and subtle defects of paracentral scotomas on serial HVFs. The NFL swelling was also documented on serial GDx and was worse in the eye first affected. Case 1 also showed a small paracentral scotoma on FDT, while case 2 had an elevated NSE titer and both these abnormalities preceded the subacute visual loss which, for both patients, occurred about two years after the investigations were initiated. Conclusions: We describe two members of our very large Brazilian pedigree of 11778 LHON (J–haplogroup) who were asymptomatic Carriers yet demonstrated some impairments on fundus and psychophysical assessments. Our large prospective study of Carriers provided the singular opportunity to document several subtle psychophysical defects that preceded the classical severe visual loss associated with LHON conversion to the Affected status.

Keywords: neuro-ophthalmology: optic nerve • optic disc • neuro-ophthalmology: diagnosis