Hydroxykynureninuria

Hydroxykynureninuria, also known as kynureninase deficiency, is a very rare inherited metabolic disorder. It affects the way the body breaks down tryptophan, an amino acid found in many foods we eat. Normally, the body uses an enzyme called kynureninase to process a substance called hydroxykynurenine. When this enzyme does not work properly, hydroxykynurenine and related compounds build up in the blood and are passed out in the urine in large amounts. Most people with hydroxykynureninuria do not have severe symptoms, and many cases have been found by chance during routine urine screening. Some individuals may experience mild intellectual disability or learning difficulties, and there are reports of skin sensitivity to sunlight (a pellagra-like rash), similar to what happens when the body is low in vitamin B3 (niacin). This happens because the normal pathway that makes niacin from tryptophan is blocked. Treatment is generally straightforward and may involve vitamin B6 (pyridoxine) supplementation, since kynureninase depends on vitamin B6 to work. Niacin supplementation may also be recommended to replace what the body cannot make on its own. The overall outlook for most people with this condition is considered good, especially with appropriate nutritional support.

Bring these to your next appointment

• Q1.What dose of vitamin B6 and niacin do you recommend for my specific situation?,How often should I have urine and blood tests to monitor my condition?,Do I need to follow any special diet, or are supplements enough?,Should other family members be tested for this condition?,Are there any long-term complications I should watch for?,Should I see a dietitian who specializes in metabolic disorders?,Are there any research studies or registries I can join to help advance understanding of this condition?

Common questions about Hydroxykynureninuria

Related conditions

Other rare diseases commonly researched alongside Hydroxykynureninuria.

• Hartnup disease→
• Pellagra→