What else is it called?
- BTD deficiency
- late-onset biotin-responsive multiple carboxylase deficiency
- late-onset multiple carboxylase deficiency
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What causes it?
Biotinidase Deficiency is caused by a problem in the BTD gene. This gene produces the biotinidase enzyme, which is required to help the body recycle the vitamin biotin. This process is needed to help convert food into energy.
If you have a problem in the BTD gene, you will not produce enough of the biotinidase enzyme. Therefore, you will be unable to recycle the biotin vitamin, which causes toxic chemicals to build up and damage cells and tissue in your body.
How common is it?
Biotinidase Deficiency, in all its variations, affects around 1 in every 60,000 people.
This disorder has two variations, which each have different a prevalence. Profound Biotinidase Deficiency affects 1 in 140,000 people, whereas Partial Biotinidase Deficiency affects 1 in 110,000 people.
Around 1 person in every 120 is a carrier of Biotinidase Deficiency. It has been observed that people of Hispanic descent are more likely to be affected by the disorder, whilst the African American population has lower rates. Further, an increase in cases of Biotinidase Deficiency has been linked to countries with high rates of consanguineous marriages.
What are the signs and symptoms?
The symptoms of Biotinidase Deficiency depend on which form of the condition you have. For Profound Biotinidase Deficiency, which is typically more severe, symptoms include:
- Weak muscle tone (hypotonia)
- Breathing problems
- Delayed development.
If left untreated, the disorder can cause:
- Hearing loss
- Eye abnormalities and loss of vision
- Problems with movement and balance (ataxia)
- Skin rashes
- Hair loss (alopecia)
- A fungal infection called candidiasis
The milder form of this disorder, called Partial Biotinidase Deficiency, has some similar symptoms. These symptoms may occur regularly, but they sometimes only show during periods of illness or stress. These include:
- Weak muscle tone
- Skin rashes
- Hair loss
People with Biotinidase Deficiency can expect to live a healthy life, but it is important to follow any management plans given to you by your medical team in order to stop your symptoms from getting worse.
How is it diagnosed?
Diagnosis is based on identification of the clinical symptoms and a specialised blood test. A genetic test is used to confirm the diagnosis.
Some countries offer newborn screening for Biotinidase Deficiency, including the USA. However, this disorder is not currently part of the newborn screening test in the UK.
The presentation of Biotinidase Deficiency is similar to other metabolic disorders, such as Holocarboxylase Synthetase Deficiency, Isolated Carboxylase Deficiency, Nutritional Biotin Deficiency, Zinc Deficiency, and Essential Fatty Acid Deficiency.
Can it be treated?
There are treatments available for Biotinidase Deficiency. Most commonly, you will be given oral biotin to replace the vitamins your body cannot produce. This will be prescribed by your doctor in the strength that is most suitable for you, and you will need to keep taking biotin for the rest of your life.
This treatment is most effective when started before the symptoms of the disorder show. If treatment is started after the symptoms have appeared, then they cannot be reversed. This is particularly related to eye and hearing problems, as well as developmental delays.
Supportive treatment will focus on reducing the impact of any symptoms you may have. This can include extra support to help with development, physical therapy to strengthen muscles and help movement, aids to help with hearing or sight loss, and medication to manage skin problems. These will be tailored to your specific needs which you can discuss with your medical team.
Many people with Biotinidase Deficiency go on to lead healthy lives, especially when treatment is started early. It is important to follow your medical team’s advice in order to stop the symptoms from getting worse.
Do my family need to be tested?
Biotinidase Deficiency is inherited from both parents in an autosomal recessive inheritance pattern. This means that both parents are carriers of the disorder through their genes.
All genes come in pairs. Carriers of Biotinidase Deficiency have one working BTD gene and one faulty gene. Children inherit one gene from each parent to make their pair. Whether you have Biotinidase Deficiency depends on the genes you inherit:
There is a 50% chance that the child will inherit one faulty and one working gene, which means they will also be a carrier.
- There is a 25% chance that the child will inherit two working genes and not inherit or carry the faulty gene.
- There is a 25% chance that the child will inherit two faulty genes, which means they will have Biotinidase Deficiency.
If you think you, or somebody in your family, may have Biotinidase Deficiency, or that you may be a carrier, contact your medical team who may refer you for genetic testing.