Gene-environment interactions in Leber hereditary optic neuropathy.

Leber hereditary optic neuropathy (LHON) is a genetic disorder primarily due to mutations of mitochondrial DNA (mtDNA). Environmental factors are thought to precipitate the visual failure and explain the marked incomplete penetrance of LHON, but previous small studies have failed to confirm this to be the case. LHON has no treatment, so identifying environmental triggers is the key to disease prevention, whilst potentially revealing new mechanisms amenable to therapeutic manipulation. To address this issue, we conducted a large, multicentre epidemiological study of 196 affected and 206 unaffected carriers from 125 LHON pedigrees known to harbour one of the three primary pathogenic mtDNA mutations: m.3460G>A, m.11778G>A and m.14484T>C. A comprehensive history of exposure to smoking, alcohol and other putative environmental insults was collected using a structured questionnaire. We identified a strong and consistent association between visual loss and smoking, independent of gender and alcohol intake, leading to a clinical penetrance of 93% in men who smoked. There was a trend towards increased visual failure with alcohol, but only with a heavy intake. Based on these findings, asymptomatic carriers of a LHON mtDNA mutation should be strongly advised not to smoke and to moderate their alcohol intake.

Cortical brain malformations: effect of clinical, neuroradiological, and modern genetic classification.

BACKGROUND: Malformations of cortical development (MCDs) are a major source of handicap. Much progress in understanding the genetic causes has been made recently. The number of affected children in whom a molecularly confirmed diagnosis can be made is unclear. OBJECTIVE: To evaluate the etiology of MCDs in children and the effect of a combined radiological, clinical, and syndrome classification. DESIGN: A case series of 113 children with a radiological diagnosis of MCD from January 1, 1992, to January 1, 2006. SETTING: The Erasmus Medical Center-Sophia Children's Hospital, a secondary and tertiary referral center. PATIENTS: Patients with MCD underwent a complete radiological, clinical, and neurological assessment and testing for known genes involved in the pathogenesis of MCD as appropriate for their phenotype. RESULTS: We established an etiological diagnosis in 45 of 113 cases (40%). For 21 patients (19%), this included molecular and/or genetic confirmation (Miller-Dieker syndrome; LIS1, DCX, FLNA, EIF2AK3, or KIAA1279 mutations; or an inborn error of metabolism). In 17 (15%), a syndrome with an unknown genetic defect was diagnosed. In 7 patients (6%), we found evidence of a gestational insult. Of the remaining 68 patients, 34 probably have a yet-unknown genetic disorder based on the presence of multiple congenital anomalies (15 patients), a family history with multiple affected persons (12 patients), or consanguineous parents (7 patients). CONCLUSIONS: In our cohort, combining diagnostic molecular testing with clinical, radiological, and genetic classification; syndrome identification; and family study provided a diagnosis in 40% of the cases of MCD. This contributes to the possibility of prenatal diagnosis and improved patient treatment and disease management.

A MELAS-associated ND1 mutation causing leber hereditary optic neuropathy and spastic dystonia.

OBJECTIVE: To report a novel mutation that is associated with Leber hereditary optic neuropathy (LHON) within the same family affected by spastic dystonia. DESIGN: Leber hereditary optic neuropathy is a mitochondrial disorder characterized by isolated central visual loss. Of patients with LHON, 95% carry a mutation in 1 of 3 mitochondrial DNA-encoded complex I genes. The complete mitochondrial DNA was screened for mutations in a patient with LHON without 1 of these 3 primary mutations. The heteroplasmy level and biochemical consequence of the mutation were determined. RESULTS: A pathogenic 3697G>A/ND1 mutation was detected and seemed associated with an isolated complex I deficiency. This family has similar clinical characteristics as the previously described families with LHON and dystonia with an ND6 mutation. CONCLUSIONS: The 3697G>A/ND1 mitochondrial DNA mutation causes the LHON and spastic dystonia phenotype in the same family. This mutation can also cause MELAS syndrome (which encompasses mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke), and other genetic factors may contribute to the clinical expression.

Quality of life in patients with leber hereditary optic neuropathy.

PURPOSE: Leber hereditary optic neuropathy (LHON) is an inherited mitochondrial optic neuropathy characterized by bilateral, severe loss of central vision. In this study, the first formal assessment was conducted of visual disability in affected and unaffected individuals from molecularly confirmed LHON pedigrees. METHODS: Four hundred two LHON carriers--196 affected and 206 unaffected--from 125 genealogically distinct pedigrees were prospectively interviewed using the well-validated visual function index (VF-14) questionnaire: m.3460G>A (n = 71), m.11778G>A (n = 270), and m.14484T>C (n = 61). RESULTS: The mean age of onset of visual loss was 27.9 years (SD, 14.9) and mean disease duration was 15.5 years (SD, 15.4), with 74.5% of the affected subjects being men. The mean VF-14 score was 25.1 (SD, 20.8) in the affected patients, compared with 97.3 (SD, 7.1) in the unaffected carriers. Within the affected group, VF-14 score did not worsen with increasing disease duration and individuals with the m.14484T>C mutation had higher VF-14 scores compared with those in the m.3460G>A and m.11778G>A groups. Reading small print and reading a newspaper or book were the two VF-14 items that presented the greatest difficulty. CONCLUSIONS: LHON has a severe negative impact on quality of life and has the worst VF-14 score when compared with other previously studied ophthalmic disorders. However, affected LHON carriers can be reassured that their level of visual impairment is unlikely to progress with time. The VF-14 questionnaire will be a useful tool for assessing the natural history of LHON and measuring outcome in future treatment trials.