Summary

Alpha-N-acetylgalactosaminidase (NAGA) deficiency is a lysosomal storage disease classified among the oligosaccharidoses or glycoproteinoses. The prevalence remains unknown: only about twelve cases from eight families have been reported. The disorder is clinically heterogeneous. An infantile form (Schindler disease) was initially reported in two brothers: onset occurred by the end of the first year with progressive hypotonia, extra-pyramidal signs and rapid psychomotor regression (myoclonic epileptic seizures, spastic quadriplegia, blindness, loss of contact with the outer world). A possible association with another cause of neuroaxonal dystrophy has been discussed. A few adult cases have been reported with angiokeratomas similar to those found in Fabry disease and moderate intellectual deficit(Kanzaki disease). Intermediate forms have also been observed with behavioural disturbances, epileptic seizures and variable psychomotor retardation. The syndrome is transmitted as an autosomal recessive trait. The causative gene is located on 22q13 and several mutations have been identified. The biological diagnosis is made upon finding a characteristic profile on chromatography of urinary oligosaccharides, and is confirmed by the measurement of NAGA activity in leucocytes, fibroblasts, amniocytes, or the trophoblast. Treatment remains symptomatic.

Expert reviewer(s)

• Dr Roseline FROISSART
• Dr Irène MAIRE