Neuraminidase deficiency, commonly known as sialidosis, is a lysosomal storage disorder, characterized by a deficiency of the enzyme alpha-N-acetyl neuraminidase (sialidase). Sialidosis is classified into two main forms based on the phenotypic features. Type I sialidosis is typified by symptoms of myclonic epilepsy, visual problems, ataxia, and most characteristically, the presence of macular cherry red spots in the second or third decade of their life. This form of the disease is often referred to as cherry red spot-myoclonus syndrome. Sialidosis type II is a more severe form of the disease, typically present with an earlier onset of disease. In fact, type II sialidosis can present in a congenital or an infantile form; both proving fatal before the third year of life. The most severe form of the disease occurs in utero, resulting in still birth or death within a few months after birth. Typical symptoms of sialidosis in infants include flat nasal bridge, puffy eyelids, enlargement of the gums and tongue, and occasionally skeletal malformations. Older children may show tremors, impaired vision, seizures, hypotonia, and mental retardation.
No cure is available for sialidosis. Treatment is aimed at the clinical features presented. Seizures are difficult to control with anti-convulsant medications. The myoclonus often interferes with walking.