Biotinidase Deficiency

Biotinidase deficiency is a recessive hereditary disorder in which the person lacks the enzyme necessary to release biotin from the protein it is chemically bound to, leading to lack of enough available biotin for the body to use. It is designated as profound or partial, depending on the degree of biotin deficiency.^{5, 10}

The condition typically presents itself any time from infancy to age 10. Some states include testing for biotinidase deficiency as part of their newborn screening procedures. The condition is diagnosed as profound biotinidase deficiency if the biotinidase enzyme activity in the blood is fewer than 10% of the normal activity, or partial if between 10-30% of normal enzyme levels.¹⁰

Most symptoms are readily alleviated with 5-10 mg of oral biotin, which is rapidly and completely absorbed by the body. However, if left untreated biotinidase-deficient children will commonly display some or all of the following symptoms:^{1, 10}

• Alopecia
• Blurry vision
• Developmental delays
• Hearing loss
• Lax muscle tone and weakness
• Neurological disorders
• Seizures
• Skin rash
• Spinal cord demyelination
• Yeast infections

Although the symptoms of biotinidase deficiency are similar to biotin deficiency caused by other factors (e.g., malnutrition), they are not identical. Some of the neurological damage associated with biotinidase deficiency (e.g., irreversible hearing loss, vision problems) is not found in biotin deficiency from non-hereditary causes nor with deficiency of holocarboxylase synthetase enzyme.⁷