Alpha-N-acetylgalactosaminidase deficiency

Alpha-N-acetylgalactosaminidase (NAGA) deficiency, also known as Schindler disease or Kanzaki disease, is a rare autosomal recessive lysosomal storage disorder caused by mutations in the NAGA gene located on chromosome 22q13.2. The enzyme alpha-N-acetylgalactosaminidase is responsible for cleaving terminal alpha-N-acetylgalactosamine residues from glycoconjugates. When this enzyme is deficient, glycopeptides and oligosaccharides accumulate in lysosomes throughout the body, leading to progressive cellular dysfunction. Three clinical forms have been described. Type I (Schindler disease, infantile form) is the most severe, presenting in infancy with progressive neurological deterioration including neuroaxonal dystrophy, seizures, cortical blindness, spasticity, and profound psychomotor regression. Type II (Kanzaki disease, adult form) is milder, presenting in adulthood with angiokeratoma, mild intellectual impairment, peripheral neuropathy, and lymphedema. Type III is an intermediate form with variable neurological involvement. The nervous system is the primary organ system affected, particularly in the infantile form, while the skin, peripheral nerves, and lymphatic system are more prominently involved in the adult form. There is currently no specific or curative treatment for alpha-N-acetylgalactosaminidase deficiency. Management is supportive and symptomatic, focusing on seizure control, physical therapy, and management of complications. Genetic counseling is recommended for affected families. Research into enzyme replacement therapy and other therapeutic approaches is ongoing but no approved disease-specific therapies exist at this time.

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