Biotinidase deficiency is a genetic metabolic disorder that affects the body’s ability to produce and possess the active enzyme biotinidase. Biotinidase is necessary for the extraction of biotin, an essential B vitamin, from food sources into a usable form as well as reusing and recycling it. This enzyme is usually found in the liver and blood serum.
Biotinidase deficiency is caused by a mutation in the BTD gene, which is responsible for the instructions on how to make the enzyme. This mutation is recessive and requires two copies of the mutant gene from both parents for the disorder to be inherited. When this mutation is inherited, biotinidase deficiency may be profoundly pronounced or partially pronounced. The difference between the two is that the individual with the profoundly pronounced disorder will have biotinidase activity that is 10% or less of what the normal biotinidase activity level should be at while individuals with the partially pronounced disorder will have biotinidase activity that is 10-30% of the normal activity level.
Individuals with biotinidase deficiency will begin exhibiting symptoms at around the first 6 months of age. These symptoms include seizures, weak development, breathing problems, and weak muscle tone. Other signs and symptoms that are more specific to this disorder include eczematous skin rash, conjuctivitis, alopecia, ataxia and candidiasis. If left untreated, babies and young children can die from brain seizures and fungal infections of the lungs due to the decreased activity of the immune system.
Diagnosis of an individual with suspected biotinidase deficiency includes testing the blood serum and plasma for the presence and activity of any biotinidase enzyme and a genetic screening for the mutant BTD gene.
Because biotinidase deficient individuals lack the enzyme necessary to extract and use biotin, the treatment is to simply have the individual take biotin supplements. In most cases, the symptoms of the disorder simply disappear, especially if a diagnosis was made early on before any neurological or other types of damage could occur. Individuals who are profoundly pronounced with the disorder will have to take a much higher dosage of biotin than those who are only partially pronounced. Individuals who are only partially pronounced with the disorder may not need to take supplements at all or only need to take supplements on an as needed basis to keep certain symptoms in check.
There is no cure for biotinidase deficiency. The best outcome for babies born with this disorder is a quick diagnosis for the symptoms that start to develop followed by the necessary treatment of biotin supplements. Adults who may think they are carriers or have other family members who have this disorder may get themselves tested before starting a family to help determine if their children may be more likely to inherit this disorder.
