This is a rare neurological disorder with primary symptoms of muscle stiffness (spasticity), balance problems, slurred speech, and movement difficulties. It is part of a large group of such conditions with similar features that are often overlapping making diagnosis difficult. Only a small number of families (less than 10) have been reported.
Symptoms of slurred speech and difficulty walking are often evident in the first two decades of life. Difficulties with balance and stiffness in the legs (spasticity) are slowly progressive and the arms may also become spastic. The eyes usually have a constant horizontal back and forth movement known as nystagmus. Tremors and purposeless movements are sometimes seen. Cognition and mental function are normal in the majority of individuals. Most patients remain ambulatory throughout their lives.
This is an autosomal recessive condition in which mutations must be present in both of a specific pair of genes before the symptoms appear. The parents, who each carry only one mutated gene (carriers), are clinically normal but confer a risk of 25% for this disorder to each of their children.
A neurologist is most likely to make this diagnosis. Although all of the signs and symptoms are slowly progressive, most patients remain mobile and are able to care for themselves throughout their lives. Physical and speech therapy might be helpful.