Alpha-N-Acetylgalactosaminidase Deficiency Type 2

A very rare mild adult type of NAGA deficiency with the features of angiokeratoma corporis diffusum and mild sensory neuropathy.

Epidemiology

Prevalence of this disorder is not known but less than 20 cases have been reported to date for NAGA deficiency.

Clinical description

This disorder is clinically heterogeneous. Some patients have been reported to have, in addition to angiokeratoma, mild intellectual impairment, but no neurologic signs. Another patient had lymphedema, cardiomegaly, corneal opacity and slight facial coarsening including thick lips, a depressed nasal bridge and an enlarged tip of the nose. Other facultative features consist of tinnitus, hearing loss and vertigo (Meniere disease) (see this term). Pathological characteristics are comprised of vacuolization seen in the blood and dermal cells including the endothelial cells of blood and lymphatic vessels, pericytes, fibrocytes, fat cells, Schwann cells, axons, arrector pili smooth muscle cells, and eccrine sweat gland cells. Vacuolization is most prominent in vascular endothelial cells and the secretory portion of sweat glands.

Etiology

Different causal homozygous mutations of the NAGA gene (22q13.2) have been described in the reported patients. These mutations lead to the dysfunction, instability and rapid degradation of the lysosomal protein, NAGA. Lack of this enzyme activity leads to impaired catabolism and accumulation of undegraded glycoconjugates in the tertiary lysosomes.

Genetic counseling

Transmission is autosomal recessive and genetic counseling is possible.