What is sialidosis?

Sialidosis is a genetic neurodegenerative disease. The hallmark of this group of disorders is a slow but progressive deterioration of brain function. There are actually four categories of genetic neurodegenerative disorders: sphingolipidoses, neuronal ceroid lipofuscinoses, adrenoleukodystrophy, and sialidosis. These may be distinguished from one another based on head CT, head MRI, nerve conduction velocities, visual evoked potentials, auditory evoked potentials, electroretinography, and to a lesser extent, EEG's. When needed, skin, conjunctival, and nerve biopsies can help pinpoint the diagnosis.

Sialidosis is divided into sialidosis type I and sialidosis type II. These conditions are caused by a missing enzyme (called sialidase or alpha-neuraminidase) that results in the accumulation of sialic acid in the nerve cells. Type I is usually first noted in teenagers who develop visual changes and abnormal movements. Type II can show up in infants and toddlers.

One of the most interesting developments in the treatment of sialidosis happened by accident. In Japan, two children who were missing the key enzyme (sialidase) began producing it when they got Epstein Barr virus! Further research is now underway regarding the therapeutic possibilities of this fortuitous occurrence (J Neurol Sci, Jul 1995).

Currently, researchers are also trying to understand the possible roles that bone marrow transplantation and gene therapy may play in treating these conditions.