Metabolic Study in a Boy with Biotinidase Deficiency

Overview

A 12-month-old boy was referred to the metabolic centre because of a 4-week history ofvomiting, diarrhoea, progressive muscular hypotonia, mycotic skin infection and partialalopecia. He had severe metabolic acidosis compensated by hyperventilation (pCO2 17 mmHg).Laboratory investigations revealed hyperlactacidaemia (9.7 mmol/l) and hyperalaninaemia(830 mmol/l). Increased excretion of 3-OH-isovaleric acid (925mg/g creatinine) and lactic acid (11 496 mmol/mol creatinine) were found in urine.Biotinidase deficiency was suspected because of concomitant neurologic abnormalities,dermatological symptoms and metabolic disturbances. The diagnosis of biotinidasedeficiency was confirmed by enzymatic assay in plasma (biotinidase activity 0.4 nmolPABA/min/ml, controls 5.5 - 10.2 nmol PABA/min/ml). Activity of biotidinase in parents,brother and in three other relatives were between 17 - 70% of controls. Within severaldays after beginning of treatment with biotin (20 mg/day) total clinical recovery andnormalisation of hyperlactacidaemia were observed. Up to now the boy’s psychomotordevelopment is normal, only MR study of the brain carried out 9 months after the beginningof treatment showed the same cortical atrophy as before therapy. Although the incidence ofbiotinidase deficiency is estimated at 1 per 40 000 births, to our knowledge this is thefirst case in the Czech Republic and only the second one in the region of the formerCzechoslovak Republic. We suppose that some children with biotinidase deficiency are lostunrecognised. Children with treated biotinidase deficiency have a good prognosis, but aprolonged follow-up is necessary.

Key words:
biotionidase deficiency, lactic acidosis