What are the other Names for this Condition? (Also known as/Synonyms)

• Biotin Deficiency Disorder
• BTD Deficiency Disorder
• Late-Onset Biotin-Responsive Multiple Carboxylase Deficiency Disorder

What is Biotinidase Deficiency Disorder? (Definition/Background Information)

• Biotinidase Deficiency Disorder is an inherited disorder in which the body is unable to recycle the vitamin biotin. The disorder may become apparent in the first few months of life, or later in childhood
• The more severe form of the disorder is called 'Profound Biotinidase Deficiency' and may cause delayed development, seizures, weak muscle tone (hypotonia), breathing problems, hearing and vision loss, problems with movement and balance (ataxia), skin rashes, hair loss (alopecia), and a fungal infection called candidiasis
• The milder form is called 'Partial Biotinidase Deficiency'; without treatment, affected children may experience hypotonia, skin rashes, and hair loss
• In some cases, these symptoms only appear during illness, infection, or other times of stress on the body. Biotinidase Deficiency Disorder is caused by mutations in the BTD gene and is inherited in an autosomal recessive manner
• Lifelong treatment with biotin can prevent symptoms and complications from occurring or improve them if they have already developed

(Source: Biotinidase deficiency; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

Who gets Biotinidase Deficiency Disorder? (Age and Sex Distribution)

• Biotinidase Deficiency Disorder is a rare congenital disorder. The presentation of symptoms may occur immediately following the birth of the child or during early childhood
• Both males and females may be affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Biotinidase Deficiency Disorder? (Predisposing Factors)

• A positive family history may be an important risk factor, since Biotinidase Deficiency Disorder is an inherited condition
• Currently, no other risk factors have been clearly identified for this deficiency disorder

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Biotinidase Deficiency Disorder? (Etiology)

• The exact cause of development of Biotinidase Deficiency Disorder is presently unknown
• It is a genetic disorder involving the BTD gene that is inherited in an autosomal recessive manner

Autosomal recessive: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).

What are the Signs and Symptoms of Biotinidase Deficiency Disorder?

The signs and symptoms of Biotinidase Deficiency Disorder typically appear within the first few months of life, but the age of onset varies. Children with profound Biotinidase Deficiency Disorder, the more severe form of the condition, may have seizures, weak muscle tone (hypotonia), breathing problems, and delayed development. If left untreated, the disorder can lead to hearing loss, eye abnormalities and loss of vision, problems with movement and balance (ataxia), skin rashes, hair loss (alopecia), and a fungal infection called candidiasis.

Partial Biotinidase Deficiency is a milder form of this condition. Affected children may experience hypotonia, skin rashes, and hair loss, but these problems may appear only during illness, infection, or other times of stress on the body.

The signs and symptoms of Biotinidase Deficiency Disorder may include:

• Conjunctivitis
• Diarrhea
• Diffuse cerebellar/cerebral atrophy
• Feeding difficulties in infancy
• Generalized hypotonia
• Hepatomegaly
• Hyperammonemia
• Organic aciduria
• Recurrent skin infections
• Seborrheic dermatitis
• Seizures
• Sensorineural hearing impairment
• Skin rash
• Splenomegaly
• Tachypnea
• Visual loss
• Vomiting

Based on the frequency of symptoms observed, the following information may be noted:

Very frequently present symptoms in 80-99% of the cases:

• Generalized myoclonic seizures
• Metabolic ketoacidosis
• Muscular hypotonia

Frequently present symptoms in 30-79% of the cases:

• Alopecia 
• Ataxia
• Desquamation of skin soon after birth
• Hearing impairment 
• Keratoconjunctivitis
• Optic atrophy 
• Perioral eczema

Occasionally present symptoms in 5-29% of the cases:

• Apnea 
• Coma 
• Growth delay 
• Hypertonia 
• Hyperventilation 
• Iris hypopigmentation
• Laryngeal stridor 
• Lethargy 
• Myopia 
• Recurrent fungal infections 
• Visual field defect

(Source: Biotinidase deficiency; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How is Biotinidase Deficiency Disorder Diagnosed?

Biotinidase Deficiency Disorder is diagnosed on the basis of the following information:

• Complete physical examination
• Thorough medical history evaluation
• Assessment of signs and symptoms
• Laboratory tests
• Imaging studies
• Biopsy studies, if necessary

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Biotinidase Deficiency Disorder?

The complications of Biotinidase Deficiency Disorder may include:

• Visual and hearing impairment
• Emotional stress due to cosmetic concerns
• Reduced quality of life

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Biotinidase Deficiency Disorder Treated?

• Immediate and lifelong treatment of Biotinidase Deficiency Disorder with biotin supplements can prevent symptoms and complications from occurring or improve them if they have already developed

(Source: Biotinidase deficiency; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How can Biotinidase Deficiency Disorder be Prevented?

Currently, Biotinidase Deficiency Disorder may not be preventable, since it is a genetic disorder.

• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

Regular medical screening at periodic intervals with tests and physical examinations are recommended.

What is the Prognosis of Biotinidase Deficiency Disorder? (Outcomes/Resolutions)

• The prognosis of Biotinidase Deficiency Disorder is dependent upon the severity of the signs and symptoms and associated complications, if any
• Individuals with mild conditions have better prognosis than those with severe symptoms and complications
• Typically, the prognosis may be assessed on a case-by-case basis

Additional and Relevant Useful Information for Biotinidase Deficiency Disorder:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/