Biotinidase deficiency

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Biotinidase deficiency is a rare autosomal recessive condition in which the body is unable to break down the conjugated form of biotin (vitamin B7), resulting in low levels of bioavailable biotin, and clinical biotin deficiency.

Epidemiology

Profound deficiency (<10% of normal level) is estimated at ~1:100,000 of newborns. Profound or partial deficiency (<30% of normal level) is estimated at ~1:60,000 newborns.

Clinical presentation

Symptoms usually present in infancy with :

  • lethargy
  • anorexia
  • hypotonia
  • developmental delay
  • alopecia
  • seborrheic dermatitis
  • conjunctivitis and mucositis
  • erythematous rash
  • seizures
  • ataxia
  • lactic acidemia

In the long term if untreated, hearing loss and optic atrophy can also occur .

Radiographic features

In biotinidase deficiency in children the neuroimaging findings are relatively non-specific .

CT
  • diffuse cerebral and white matter atrophy
  • dilation of the ventricles and extra-axial CSF spaces
MRI
  • T1:
    • diffuse or patchy signal abnormalities within cerebral and cerebellar white matter
    • subcortical cyst formation
  • T2: 
    • same changes as above
    • signal abnormalities of the spinal cord may also be seen
  • DWI: areas of restricted diffusion within the signal abnormalities
  • MR spectroscopy:
    • sometimes elevated lactate
    • reduced NAA

Treatment and prognosis

Improves with megadoses of supplemental biotin, which helps with diagnosis.

Biotinidase deficiency meets the major criteria for newborn screening in multiple countries.

Differential diagnosis

See also