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Published on: October 21, 2014
Saposin B-Deficient Metachromatic Leukodystrophy Mimicking Acute Flaccid Paralysis
Priyanka Madaan1, Prashant Jauhari1, Biswaroop Chakrabarty1
1Department of Pediatrics, Child Neurology Division, All India Institute of Medical Sciences, New Delhi, India.
Abstract:
Metachromatic leukodystrophy (MLD) is a rare sphingolipid storage disorder caused by arylsulfatase A (ARSA) deficiency, resulting in central and peripheral demyelination. However, an uncommon form of MLD caused by saposin B deficiency is also described (around 10 mutations reported till date). MLD is a systemic disorder affecting the central and peripheral nervous system, gall bladder, and kidneys. Acute flaccid paralysis as the initial clinical presentation is previously known in ARSA-deficient MLD. Hereby, we report a child with acute flaccid paralysis with brain magnetic resonance imaging showing nonspecific periventricular leukodystrophy. He had progressive cognitive decline with gall bladder polyposis. ARSA levels were within normal limits. Leukodystrophy gene panel revealed a homozygous pathogenic deletion (Lys227del variant) in prosaposin (PSAP) gene. Hence, a final diagnosis of saposin B-deficient MLD was established. The index case highlights the importance of clinical and electrophysiological clues in the diagnosis of such atypical presentations of MLD.
Insights
Metachromatic leukodystrophy (MLD) can present atypically. This case reveals saposin B deficiency as a cause of MLD, emphasizing diagnostic clues for rare neurological disorders.
Area of Science:
- Neurology
- Genetics
- Rare Diseases
Background:
- Metachromatic leukodystrophy (MLD) is a rare sphingolipidosis typically caused by arylsulfatase A (ARSA) deficiency.
- It leads to central and peripheral nervous system demyelination, also affecting other organs.
Observation:
- A child presented with acute flaccid paralysis, cognitive decline, and gall bladder polyposis.
- Brain MRI showed nonspecific periventricular leukodystrophy, and ARSA levels were normal.
Findings:
- Genetic analysis identified a homozygous pathogenic deletion in the prosaposin (PSAP) gene, confirming saposin B-deficient MLD.
- This highlights an uncommon MLD subtype caused by saposin B deficiency.
Implications:
- This case underscores the importance of considering genetic testing for saposin B deficiency in MLD presentations.
- Clinical and electrophysiological findings are crucial for diagnosing atypical MLD cases, especially when ARSA levels are normal.
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