Pelizeaus-Merzbacher Disease
Patient Information
Characteristics
Background and History
This disorder belongs to a group of neurodegenerative disorders called leukodystrophies in which there is a deterioration of the nerve covering known as myelin. It is named after a German neurologist, Friedrich Christoph Pelizaeus, and a German psychiatrist, Ludwig Merzbacher who separately reported the features of this disease at about the beginning of the 20th century.
Clinical Correlations
Similar to many heritable disorders, Pelizaeus-Merzbacher disease has a variable presentation. It is an X-linked condition affecting primarily males. In severe cases, the onset is evident within a week or two of birth with unsteadiness, floppy muscles, weakness, breathing difficulties, and even seizures. To-and-from movements of the eyes are a useful diagnostic sign even at this early sign. Later, the muscles become stiff and more spastic and balance is poor. Infants affected early and severely may never speak or walk, whereas those more mildly affected may acquire these skills only to lose them later. Cognitive delays are common. Survival to the sixth decade of life is common but those with the most severe form of disease may not live beyond the second decade.
Female carriers are usually neurologically normal but some have mild gait or motor problems.
Genetics
Inheritance
This is an X-linked recessive condition in which only males have the full spectrum of disease. Mothers who are carriers can expect that half their male children will be affected.
Pedigree
X-linked recessive, carrier mother
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the mother, she usually does not have the disease since the normal X chromosome without the mutation neutralizes the mutation in the abnormal X chromosome. However, half her sons will inherit the mutation-containing X chromosome and therefore have the X-linked disease. Half the daughters will inherit the mutation-bearing X chromosome and are usuallly healthy 'carriers'.
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the mother, she usually does not have the disease since the normal X chromosome without the mutation neutralizes the mutation in the abnormal X chromosome. However, half her sons will inherit the mutation-containing X chromosome and therefore have the X-linked disease. Half the daughters will inherit the mutation-bearing X chromosome and are usuallly healthy 'carriers'.
Diagnosis and Prognosis
There is no effective treatment for this disorder. Some measure of seizure control can be achieved with medications. Infants and children with breathing difficulties may benefit from placement of a breathing tube. Some patients require a feeding tube to maintain adequate nutrition.
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