Subclinical carriers and conversions in Leber hereditary optic neuropathy: a prospective psychophysical study.

PURPOSE: The authors previously presented the results of their 2001 field investigation to rural Brazil to investigate a 336-member pedigree of Leber hereditary optic neuropathy (LHON). The present work describes the yearly field investigations 2001 to 2005, utilizing a variety of highly sophisticated psychophysical and electrophysiologic procedures, in asymptomatic LHON carriers, some of whom converted to affected status. METHODS: Careful, repeated examinations of 75 carriers of homoplasmic 11778 LHON mtDNA J-haplogroup mutants were performed as part of the field investigation of this pedigree. All subjects underwent a detailed neuro-ophthalmologic investigation, including formal visual fields (Humphrey; HVF) and fundus photography. In addition, many subjects underwent rigorous psychophysical examination, including Cambridge Research Systems color vision and contrast sensitivity testing, OCT, GDx, and multifocal visual evoked response (mfVER) and multifocal electroretinogram (mfERG). Two patients followed as nonsymptomatic LHON carriers converted to affected status. RESULTS: Many LHON carriers did, in fact, show subclinical or occult abnormalities. Focal edema was often seen involving the arcuate nerve fiber bundles, and this corresponded with areas of relative paracentral or arcuate scotomas on HVF testing. Compared to controls, LHON carriers had significant losses in color vision affecting mostly the red-green system and reduction in spatial but not temporal contrast sensitivity. The mfVER and mfERG data showed that most carriers had depressed central responses and abnormal interocular asymmetries. CONCLUSIONS: In this very large pedigree of 11778 LHON, the carriers frequently showed manifestations of optic nerve impairments. Their occult disease reflected low-grade compromise that waxed and waned. In two cases, these changes led to a crescendo of dramatic impairments that characterize conversion to affected status.

Extensive investigation of a large Brazilian pedigree of 11778/haplogroup J Leber hereditary optic neuropathy.

PURPOSE: To conduct systematic epidemiologic, neuro-ophthalmologic, psychophysical, and mitochondrial DNA (mtDNA) genetic examinations on a newly identified pedigree with Leber hereditary optic neuropathy (LHON). DESIGN: Observational population cohort study. METHODS: A prospective investigation of an entire Brazilian LHON family. SETTING: A field investigation by an international team conducted in a remote part of Brazil. STUDY POPULATION: We evaluated 265 (both eyes) of the 328 living family members of this LHON pedigree. Only members of this pedigree were studied. Those entering the pedigree as spouses were used as controls. OBSERVATION PROCEDURES: We conducted epidemiologic interviews emphasizing possible environmental risk factors, comprehensive neuro-ophthalmologic examinations, psychophysical tests, Humphrey visual field studies, fundus photography, and blood testing for mitochondrial genetic analysis. RESULTS: We reconstructed a seven-generation maternal lineage descended from a common ancestor dating to the 1870s. All maternally related family members were invariably homoplasmic 11778 with a haplogroup J mtDNA, 33 being affected, of which 22 are still living. With each subsequent generation, there was a progressive decrease of penetrance, and only males were affected in the last two generations. A significant exposure (greater than 95% confidence intervals) to a variety of environmental risk factors characterized the affected individuals, with smoking as the most common (P <.01). Both affected and carriers (95% confidence intervals) presented with a significantly lower incidence of hypertension and high cholesterol compared with the control group (P <.05). CONCLUSIONS: Almost 95% of a 328-living-member pedigree with LHON 11778/J haplogroup was comprehensively studied. Our initial results indicate the strong influence of environmental risk factors. The remarkably reduced incidence of cardiovascular risk in the maternal lineage is discussed. Further genetic analysis may reveal a role for the nuclear genome.

A very large Brazilian pedigree with 11778 Leber's hereditary optic neuropathy.

PURPOSE: We conducted extensive epidemiological, neuro-ophthalmological, psychophysical, and blood examinations on a newly discovered, very large pedigree with molecular analysis showing mtDNA mutation for Leber's hereditary optic neuropathy (LHON). METHODS: Four patients representing four index cases from a remote area of Brazil were sent to Sao Paulo, where complete ophthalmological examinations strongly suggested LHON. Molecular analysis of their blood demonstrated that they were LHON, homoplasmic 11778, J-haplogroup. They had an extensive family that all lived in one rural area in Brazil. To investigate this family, we drew on a number of international experts to form a team that traveled to Brazil. This field team also included several members of the Federal University of Sao Paulo, and together we evaluated 273 of the 295 family members that were still alive. We conducted epidemiological interviews emphasizing possible environmental risk factors, comprehensive neuro-ophthalmological examinations, psychophysical tests, Humphrey visual field studies, fundus photography, and blood testing for both mitochondrial genetic analysis and nuclear gene linkage analysis. RESULTS: The person representing the first-generation case immigrated from Verona, Italy, to Colatina. Subsequent generations demonstrated penetrance rates of 71%, 60%, 34%, 15%, and 9%. The percentages of males were 60%, 50%, 64%, 100%, and 100%. Age at onset varied from 10 to 64 years, and current visual acuities varied from LP to 20/400. CONCLUSIONS: Almost 95% of a nearly 300-member pedigree with LHON 11778 were comprehensively studied. Analysis of environmental risk factors and a nuclear modifying factor from this group may help address the perplexing mystery of LHON: Why do only some of the genetically affected individuals manifest the disease? This fully described database may also provide an excellent opportunity for future clinical trials of any purported neuroprotective agent.