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Delayed-onset profound biotinidase deficiency
B Wolf1, R J Pomponio, K J Norrgard
1Department of Human Genetics, Medical College of Virginia/Virginia Commonwealth University, Richmond 23298, USA.
Insights
Biotinidase deficiency can manifest later in childhood or adolescence with limb weakness and vision issues. This rare genetic disorder requires consideration in older children presenting with these neurological and ophthalmological symptoms.
Area of Science:
- Biochemistry
- Genetics
- Pediatrics
Background:
- Biotinidase deficiency typically presents in infancy or early childhood.
- Characteristic symptoms include developmental delay, seizures, and skin rashes.
- Late-onset presentations are less common but documented.
Purpose of the Study:
- To describe late-onset biotinidase deficiency in older children and adolescents.
- To highlight atypical clinical manifestations in this patient group.
- To emphasize the importance of considering biotinidase deficiency in the differential diagnosis of later-onset neurological and visual symptoms.
Main Methods:
- Case series describing four patients with late-onset biotinidase deficiency.
- Clinical evaluation including neurological and ophthalmological examinations.
- Genetic analysis to identify mutations in the BTD gene.
Main Results:
- Four patients presented with symptoms in late childhood or adolescence.
- Common symptoms included motor limb weakness, spastic paresis, and ocular abnormalities (visual acuity loss, scotomata).
- Identical mutations were found in these patients as in early-onset cases, suggesting variable expressivity.
Conclusions:
- Biotinidase deficiency should be considered in the differential diagnosis of older children and adolescents with unexplained limb weakness, spasticity, or eye problems.
- Late-onset presentations can mimic other neurological disorders.
- Genetic analysis is crucial for confirming the diagnosis regardless of symptom onset age.
Abstract:
Children with biotinidase deficiency usually exhibit symptoms at several months to years of age. We describe four children who had symptoms later in childhood or during adolescence; they had motor limb weakness, spastic paresis, and eye problems, such as loss of visual acuity and scotomata, rather than the more characteristic symptoms observed in young untreated children with the disorder. These older children each have different mutations, but they are the same as those of children who have exhibited symptoms at an early age. Biotinidase deficiency should be considered in older children who suddenly experience limb weakness and/or spastic paresis and eye symptoms.