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A Rare and Treatable Cause for Unexplained White Matter Lesions: Partial Biotinidase Deficiency 

Clinical Genetics and Therapeutics
  • Primary Categories:
    • Clinical- Pediatric
  • Secondary Categories:
    • Clinical- Pediatric
Introduction
We report an unusual cause of a cerebral peduncle MRI lesion in a teenager with well-controlled idiopathic generalized epilepsy. To date, only a handful of cases exist on partial biotinidase deficiency. Our objective is to highlight the clinical presentation and increase awareness of this disorder to facilitate early diagnosis and improve neurological outcomes.

 

Case Presentation
A 14-year-old previously healthy girl was diagnosed with idiopathic generalized epilepsy. Her physical exam was non-focal including symmetric reflexes in the extremities and a thorough motor and sensory examination. 

 

Diagnostic Workup
As part of her epilepsy evaluation, MRI brain showed a hyperintense FLAIR signal in the right cerebral peduncle with no abnormal postcontrast enhancement. Given her physical exam and MRI brain findings, she was evaluated for neurofibromatosis type 1 (NF1). Whole exome sequence revealed compound heterozygosity for two pathogenic variants in the BTD gene suggesting a diagnosis of partial biotinidase deficiency.

Treatment and Management
Her regimen included Keppra (750mg twice daily) and Biotin (5mg daily). No further seizure episodes were observed, although the relationship to her epilepsy is unknown. 

Outcome and Follow-Up
Repeat MRI brain at 8 months showed an interval decrease in both signal intensity and size. Repeat MRI brain at 12 months pending.

Discussion
This report showcases a rare but treatable cause for unexplained MRI lesions. Prior cases have reported both white matter lesions within the brain and spinal cord (Gowda et al., 2020). In cases of unexplained white matter lesions, we encourage consideration of genetic testing of the BTD gene as partial deficiency may be missed on newborn screening due to its significant residual enzyme activity and treatment may reverse identified lesions and prevent further complications (Bhat et al., 2015). 

Conclusion
This report highlights partial biotinidase deficiency as a cause of white matter lesions in the brain. Genetic testing is crucial since treatment with biotin may reverse lesions as observed in our patient and previous case reports. Areas for future research include evaluating the risks and benefits of expanding newborn screens to include partial biotinidase deficiency, investigating the long-term neurodevelopmental outcomes with early treatment, and studying genetic and phenotypic variability. 

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