Biotinidase deficiency, also called BTD, is a rare genetic condition. People who have BTD are unable to process a vitamin called biotin. Biotin (also called vitamin B7 or vitamin H), helps the body break down food. It also plays a role in keeping hair, skin, and nails healthy. Biotin can naturally be found in eggs, mushrooms, bananas, nuts, seeds, fish, and sweet potatoes.
Biotinidase is an enzyme that helps break biotin away from the foods containing it. Once in this free form, the body can use the biotin. In people with biotinidase deficiency, this enzyme does not work properly. Thus, even if the person is taking in enough biotin through their diet, their body cannot use it. Untreated, they will start to show signs of deficiency.
Biotinidase deficiency can be classified into two subtypes based on how severe the disease is: partial BTD and profound BTD.
People with profound BTD have worse symptoms and more symptoms than people with partial BTD. In the worst case, profound BTD can lead to coma or death.
People with partial BTD may only have symptoms if they are stressed. This can occur with physical stress, such as illness, or emotional stress, such as an argument with a family member.
Symptoms of BTD can start anywhere from the first week of life until the age of ten. Most children’s symptoms begin in the first six months of life.
The first symptom is usually seizures. In a baby, those symptoms can look different than in an adult. For a baby, the symptoms of a seizure can include:
Other symptoms of BTD may include:
Biotinidase deficiency is caused by a faulty gene on chromosome 3. Every person inherits a set of 23 chromosomes from their mother and a set of 23 chromosomes from their father. In order to get biotinidase deficiency, a person must inherit the faulty gene from both their mother and their father.
Boys and girls are affected by biotinidase deficiency equally. Overall, the chance of having the disease is approximately 1 in 60,000 people worldwide.
Biotinidase deficiency is diagnosed with blood tests looking for biotinidase activity in the blood. A genetic test may also be done to confirm the exact change in the gene responsible.
As with all genetic testing, a meeting with a genetic counsellor to discuss the risks and benefits of the testing is important prior to the test.
Fortunately, BTD is easily treated by taking biotin supplements. If diagnosed early, treatment will prevent permanent damage. A patient should expect to continue biotin supplementation for life.
If a patient has hearing problems, vision problems or some developmental delay, these may not go away with treatment. For people who are diagnosed after permanent damage has occurred, the following may be helpful:
While the genetic changes that lead to BTD are random, it is possible to prevent the development of symptoms before they start. To do this, a parent must know that their child has the disorder.
Some countries in the world run routine blood tests on every new-born infant. In these places, testing for BTD is included. This is not always common practice in South Africa but is something about which new parents can ask their healthcare team.