Question: What is (are) Biotinidase deficiency ?
Answer: Biotinidase deficiency 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 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: GARD

Question: What are the symptoms of Biotinidase deficiency ?
Answer: What are the signs and symptoms of Biotinidase deficiency? The signs and symptoms of biotinidase deficiency typically appear within the first few months of life, but the age of onset varies. Children with profound biotinidase deficiency, 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. Immediate treatment and lifelong management with biotin supplements can prevent many of these complications. 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 Human Phenotype Ontology provides the following list of signs and symptoms for Biotinidase deficiency. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Muscular hypotonia 90% Seizures 90% Alopecia 50% Dry skin 50% Hearing impairment 50% Incoordination 50% Inflammatory abnormality of the eye 50% Optic atrophy 50% Skin rash 50% Abnormality of retinal pigmentation 7.5% Aplasia/Hypoplasia of the cerebellum 7.5% Hypertonia 7.5% Muscle weakness 7.5% Myopia 7.5% Reduced consciousness/confusion 7.5% Respiratory insufficiency 7.5% Skin ulcer 7.5% Visual field defect 7.5% Apnea - Ataxia - Autosomal recessive inheritance - Conjunctivitis - Diarrhea - Diffuse cerebellar atrophy - Diffuse cerebral atrophy - Feeding difficulties in infancy - Hepatomegaly - Hyperammonemia - Lethargy - Metabolic ketoacidosis - Organic aciduria - Recurrent skin infections - Seborrheic dermatitis - Sensorineural hearing impairment - Splenomegaly - Tachypnea - Visual loss - Vomiting - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.
Source: GARD