Pseudodeficiency of alpha-galactosidase A

Area of Science:

• Biochemistry
• Genetics
• Enzyme kinetics

Background:

• Fabry disease is an X-linked genetic disorder caused by deficient activity of the enzyme alpha-galactosidase A.
• Enzyme replacement therapy and substrate reduction therapy are current treatment options for Fabry disease.
• Genetic variations can lead to reduced enzyme activity without clinical manifestation.

Observation:

• A 51-year-old male presented with apparent alpha-galactosidase A deficiency, similar to Fabry disease patients.
• The individual was clinically healthy, with no symptoms or excess urinary ceramide trihexoside.
• This enzyme deficiency was familial, following X-linked inheritance patterns.

Findings:

• The observed alpha-galactosidase A deficiency was confirmed using both synthetic and natural substrates.
• Kinetic studies in cultured fibroblasts revealed increased Km and enhanced heat stability of the residual enzyme.
• Heterozygous carriers (daughters) and unaffected males (sons) were identified within the family.

Implications:

• This case highlights a genetic pseudodeficiency of alpha-galactosidase A, distinct from pathogenic Fabry disease mutations.
• Understanding such pseudodeficiencies is crucial for accurate genetic diagnosis and counseling.
• Further research into enzyme kinetics and stability can differentiate between disease-causing and benign variants.