While the balance between risks and benefits of HRT remains controversial, the decision to start HRT requires an individualized approach based on the patients context. While not applicable for all post-menopausal women, prophylactic (and therapeutic) HRT should be considered in all female carriers of a known LHON mutation given the substantial risk of vision loss associated with menopause. Epidemiology
In Northern European populations about one in 9,000 people carries one of the three primary LHON mutations. There is a prevalence of between 1:30,000 to 1:50,000 in Europe. The LHON ND4 G11778A mutation is the primary mutation in most of the world, with 70% of Northern European cases and 90% of Asian cases. Due to a Founder effect, the LHON ND6 T14484C mutation accounts for 86% of LHON cases in Quebec, Canada.More than 50% of males with a mutation and more than 85% of females with a mutation never experience vision loss or related medical problems. The particular mutation type may predict the likelihood of penetrance, severity of illness and probability of vision recovery in the affected. As a rule of thumb, a woman who harbors a homoplasmic primary LHON mutation has a ~40% risk of having an affected son and a ~10% risk of having an affected daughter.Additional factors may determine whether a person develops the signs and symptoms of this disorder. Environmental factors such as smoking and alcohol use may be involved, though studies of these factors have produced conflicting results.
Additional organs that may be affected include the kidneys and retinas of the eyes. Causes
The first episode of autonomic dysreflexia may occur weeks to years after spinal cord injury takes place, but most people at risk (80%) develop their first episode within the first year after injury. Early AD tends to be associated with less severe increases in blood pressure.One common causative factor may be an undetected urinary tract infection. The difficulty in assessing this may be complicated with the usage of indwelling or suprapubic catheters. Other causes include medication side effects and various disease processes. The use of stimulants such as cocaine and amphetamines which can result in urinary retention, and the use of CNS depressants and other psychoactive drugs can also lead to urinary retention and constipation thus leading to autonomic dysreflexia when in use over an extended period of time. Pain
Current scientific literature suggests that noxious (painful) stimuli are the primary initiators of AD. (Note: Not all noxious stimuli will cause AD. Some otherwise severe noxious stimuli in unaffected people, e.g. broken bones, may not result in AD, and may in fact even go unnoticed.) However, different studies have found that activation of pain receptors in muscle and skin below the lesion in spinal cord injured individuals did not trigger AD. These studies suggests that not all noxious stimuli are reliable triggers of AD, and because non-noxious stimuli can also trigger AD, attribution of an episode of AD to noxious stimuli may cause clinicians to overlook underlying non-noxious triggers.