Pelizaeus-Merzbacher disease is divided into classic and severe (connatal) types. Although these two types differ in severity, their symptoms can overlap.Classic Pelizaeus-Merzbacher disease is the more common type. Within the first year of life, those affected with classic Pelizaeus-Merzbacher disease typically experience weak muscle tone (hypotonia), involuntary movements of the eyes (nystagmus), and delayed development of motor skills such as crawling or walking. As the child gets older, nystagmus may improve, but other movement disorders develop, including muscle stiffness (spasticity), problems with movement and balance (ataxia), and involuntary jerking (choreiform movements). Cognitive abilities may be impaired, but speech and language are usually present.
Severe or connatal Pelizaeus-Merzbacher disease is the more severe of the two types. Symptoms are usually present at birth or develop in the first few weeks of life. Features include nystagmus, problems feeding, a whistling sound when breathing, progressive spasticity leading to joint deformities (contractures) that restrict movement, speech difficulties (dysarthria), ataxia, and seizures. Children often have short stature and poor weight gain. Those affected with connatal Pelizaeus-Merzbacher disease don't walk or develop effective use of their upper limbs. Verbal expression is usually severely affected, but comprehension may be significant.
The Human Phenotype Ontology (HPO) provides the following list of features that have been reported in people with this condition. Much of the information in the HPO comes from Orphanet, a European rare disease database. If available, the list includes a rough estimate of how common a feature is (its frequency). Frequencies are based on a specific study and may not be representative of all studies. You can use the MedlinePlus Medical Dictionary for definitions of the terms below.
|Signs and Symptoms||Approximate number of patients (when available)|
|Abnormal pyramidal signs||90%|
|Cerebral cortical atrophy||90%|
|Decreased body weight||90%|
|Limitation of joint mobility||90%|
|Progressive spastic quadriplegia||90%|
|Reduction of oligodendroglia||75%|
|Abnormality of the urinary system||50%|
|Abnormality of visual evoked potentials||50%|
|Delayed speech and language development||50%|
|Failure to thrive||50%|
|Neurological speech impairment||50%|
|Recurrent respiratory infections||50%|
|Congenital laryngeal stridor||7.5%|
|X-linked recessive inheritance||-|
Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.
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