Biotinidase deficiency (BD), biotin metabolism disorder, was first described in 1982 . It is inherited as an autosomal recessive trait.
The incidence of BD in the world is approximately 1/60.000 new-borns . Clinical manifestations include neurological abnormalities (seizures, ataxia, hypotonia, developmental delay, hearing loss and vision problems like optic atrophy), dermatological abnormalities (seborrhoeic dermatitis, alopecia, skin rash, conjunctivitis, candidiasis, hair loss), neuromuscular abnormalities (motor limb weakness, spastic paresis, myelopathy), metabolic abnormalities (ketolactic acidosis, organic aciduria, hyperammonaemia) [1–6]. Besides, respiratory problems (apnoea, dyspnoea, tachypnoea, laryngeal stridor) and immune deficiency findings (prolonged or recurrent viral/fungal infections) are associated with BD [1,3,4]. Hypotonia and seizures are the most common clinical features [4,7].
Treatment with 5-10mg of oral biotin per day results rapidly in clinical and biochemical improvement. However, once vision problems, hearing loss, and developmental delay occur, these problems are usually irreversible even if the child is on biotin therapy . Moreover, BD can lead to coma and death if the child is not treated . In some children, especially after puberty, the biotin dose is increased from 10mg per day to 20mg per day. A child with profound BD has less than 10% of mean normal serum biotinidase activity, whereas a child with partial BD has 10%–30% of mean normal serum biotinidase activity. BD can be identified by new-born screening. The BD gene is located on chromosome 3, gene locus 3p25.1 .
The age of clinic presentation varies from 1 week to 12 years or adulthood [9,10]. Two asymptomatic adults with profound BD have been reported . As BD is associated with VACTERL syndrome, annular pancreas and vascular ring malformation was reported in the literature [12,13], but they are almost certainly coincidental.