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Presymptomatic diagnosis: metachromatic leukodystrophy or pseudo arylsulphatase A deficiency?
Abstract:
Diagnosis of metachromatic leukodystrophy (MLD) was established in the proband at age 27 months. An examination of the family arylsulphatase A profile revealed that the father and younger sibling, age 2 months, had very low enzyme activities like the proband. The father, in all likelihood, had the pseudo arylsulphatase A deficiency trait, but the sibling could be either pseudodeficient or affected with MLD. The fibroblast cerebroside sulphate loading test confirmed that the father had pseudo arylsulphatase A deficiency. The test also indicated that the sibling was affected with MLD. This was confirmed by clinical evidence of neurological degeneration by 18 months.
Insights
Metachromatic leukodystrophy (MLD) diagnosis was confirmed in a young child using enzyme activity tests. Further testing differentiated between pseudo-deficiency and MLD in family members, aiding accurate diagnosis and management.
Area of Science:
- Biochemistry
- Genetics
- Pediatric Neurology
Background:
- Metachromatic leukodystrophy (MLD) is a rare genetic disorder affecting the nervous system.
- Early diagnosis is crucial for management and understanding disease progression.
- Arylsulphatase A (ARSA) enzyme deficiency is a key indicator of MLD.
Observation:
- A 27-month-old proband was diagnosed with MLD.
- Family screening revealed low ARSA enzyme activity in the father and a 2-month-old sibling.
- The father exhibited pseudo ARSA deficiency, while the sibling's status was initially uncertain.
Findings:
- Fibroblast cerebroside sulphate loading tests confirmed pseudo ARSA deficiency in the father.
- The same test indicated MLD in the sibling.
- Clinical signs of neurological degeneration appeared in the sibling by 18 months.
Implications:
- Accurate differentiation between MLD and pseudo ARSA deficiency is vital for affected families.
- Genetic testing and enzyme assays are essential for precise diagnosis in suspected MLD cases.
- Early identification allows for timely intervention and genetic counseling.