Biotinidase deficiency (Multiple carboxylase deficiency)
Incidence
Approx. 80 - 100 cases reported. Some 10 cases in Saudi Arabia. AR disorder, occur 1/40.000. The gen for biotinidase is in chromosome 3p25.
Clinical Characteristics
Progresive neuro Sx, death in 20%. Seizures in most patients, at least 75% of cases. In > 50% alopecia, skin rash. Optic atrophy 25-50%. Frequent hearing loss. Persistent laryngeal stridor may be an early sign. Any infant with seizures should be tested for biotinidase deficiency.
Precipitants
no
Provocation Tests
Biotin loading (3.5 mg/kg/d or 10 mg/d in a single dose) suppresses the excretion of related organic acids within days in biotin-responsive types (holocarboxylase synthetase mutants and biotinidase deficiency). Remember that Multiple Carboxylase Deficiency includes Holocarboxylase synthetase and Biotinidase Deficiencies.
Diagnostic Procedures
EB-serum, biotinidase levels in serum. Tandem MS in blood.