Biotinidase Deficiency Health Article

Prenatal diagnosis

If a couple has had one child with biotinidase deficiency, they can be offered prenatal testing in future pregnancies. Prenatal testing is accomplished by measuring biotinidase activity in amniotic fluid cells obtained by amniocentesis around the sixteenth week of pregnancy. Alternatively, if specific gene mutations have been identified in the parents, fetal DNA from amniotic fluid cells can be studied to test for these same mutations in the fetus. Carrier couples who are considering prenatal diagnosis should discuss the risks and benefits of this type of testing with a geneticist or genetic counselor.

Treatment and management

Treatment of the profound form of biotinidase deficiency consists of giving large doses of biotin orally. Partial deficiencies are usually treated with lower doses. The biotin must be in a free form; that is, not attached to other molecules as would be the case with the biotin found in food. Properly treated, biotinidase deficiency is not a life-threatening condition, but biotin treatment must continue throughout life. No treatment is needed before birth because the developing fetus is provided with sufficient free biotin from the mother.

Prognosis

Daily treatment with free biotin usually results in rapid improvement of the skin condition, hair regrowth, and a lessening or cessation of seizure activity. Many children whose development has been affected by biotinidase deficiency have shown some improvement after treatment. Hearing and vision losses are less reversible. Children who are diagnosed at birth through newborn screening programs rarely develop symptoms if they are started on biotin replacement therapy immediately.

BOOKS

Wolf, Barry. "Disorders of Biotin Metabolism." In Metabolic and Molecular Bases of Inherited Disease, edited by C. R. Scriver, et al. New York: McGraw-Hill, 2001.

PERIODICALS

Blanton, S. H., et al. "Fine Mapping of the Human Biotinidase Gene and Haplotype Analysis of Five Common Mutations." Human Heredity 50 (March-April 2000): 102-11.

Norrgard, K. J., et al. "Mutations Causing Profound Biotinidase Deficiency in Children Ascertained by Newborn Screening in the United States Occur at Different Frequencies Than in Symptomatic Children." Pediatric Research 46 (July 1999): 20-27.

ORGANIZATIONS

National Organization for Rare Disorders (NORD). PO Box 8923, New Fairfield, CT 06812-8923. (203) 746-6518 or (800) 999-6673. Fax: (203) 746-6481. <http://www.rarediseases.org>.

WEBSITES

"Biotinidase." Online Mendelian Inheritance in Man. <http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=253260> (May 24, 2001).

Thibodeau, D. L., and B. Wolf. "Biotinidase Deficiency. A Booklet for Families and Professionals." <http://views.vcu.edu/biotin>.

Tyler for Life Foundation Home Page. <http://www.tylerforlife.com/biotinidase.htm>.

Sallie Boineau Freeman, PhD