Loss of central vision in one eye is a hallmark of Leber’s hereditary optic neuropathy (LHON), a mitochondrial disease. Now, an analysis of online literature highlights that other organs besides the eye may be compromised in LHON patients.
The findings are reported in a study titled “Leber’s hereditary optic neuropathy is multiorgan not mono-organ,” published in the journal of Clinical Ophthalmology.
LHON is inherited through the mother’s mitochondrial mutated genes. Initially, there is the loss of central vision in one eye, followed by the other within weeks to months. Visual loss in both eyes at onset happens in 25% of the cases. However, according to this study, eyes are not the only organ affected.
Researchers searched several databases (MEDLINE, Current Contents, EMBASE, Web of Science, Web of Knowledge, LILACS, SCOPUS, and Google Scholar) and used specific search terms to look for studies reporting organ failures other than the eyes in LHON patients between 1966 and 2015.
LHON showed up as a multi-organ disorder also affecting the central nervous system, ears, endocrine organs, heart, bone marrow, arteries, kidneys, or the peripheral nervous system.
Researchers found that LHON patients, besides visual loss, also suffered from other diseases such as epilepsy, hearing loss, diabetes, cardiac problems, chronic renal failure and even muscular cramps. Those patients “… require regular follow-up investigations not to miss the point at which organs other than the eyes become clinically affected,” the study authors wrote.
Also, the type of gene mutation inherited and the number of mitochondria bearing the mutation (heteroplasmy rate) determine if other organs become affected. “For clinical manifestations of LHON, however, a heteroplasmy rate of at least 60% is required. The lower the heteroplasmy rate, the higher the chance for spontaneous recovery of the ophthalmologic compromise. The lower the heteroplasmy rate in carriers of the disease, the more likely the carrier remains unaffected,” explained the authors.
Although LHON is a genetic disease, environmental factors such as tobacco smoking and alcohol may contribute to the involvement of several organs.
So far, published studies have not specifically investigated other affected organs in LHON patients. However, future studies to detect at which point organs other than the eyes become affected in these patients may help to alleviate symptoms.