Pelizaeus-Merzbacher disease

James Garbern MD PhD (Dr. Garbern of the University of Rochester is a consultant for Genzyme, Lundbeck, and Stemcells, Inc.)
Raphael Schiffmann MD, editor. (Dr. Schiffmann, Director of the Institute of Metabolic Disease at Baylor Research Institute, received research grants from Amicus Therapeutics, Protalix Biotherapeutics, and Shire.)
Originally released April 7, 1995; last updated December 31, 2009; expires December 31, 2012
Notice: This article has expired and is therefore not available for CME credit.

This article includes discussion of Pelizaeus-Merzbacher disease, PMD, and Sudanophilic leukodystrophy. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

Pelizaeus-Merzbacher disease and the allelic disorder spastic paraplegia 2 (SPG2) are hereditary leukodystrophies caused by mutations of the proteolipid protein 1 (PLP1) gene. The clinical syndromes range from the severe connatal Pelizaeus-Merzbacher disease syndrome, characterized by congenital hypotonia, nystagmus, and stridor, to an uncomplicated spastic paraparesis syndrome. Mutations of the PLP1 gene on the X chromosome include deletion, duplication, triplication, and quadruplication of the entire gene, as well as intragenic mutations and complex rearrangements of the gene and neighboring loci. The nature of the mutation plays an important role in determining the cellular effects on oligodendrocytes, disease severity, and pattern of inheritance. In this article, the author describes the clinical features and complex molecular genetics of Pelizaeus-Merzbacher disease and spastic paraplegia 2.

Historical note and terminology

Pelizaeus-Merzbacher disease has historically been subdivided into clinical variants based on the age of onset and severity of clinical signs. "Classical" Pelizaeus-Merzbacher disease is the most common presentation and is that described by Pelizaeus (Pelizaeus 1885) and Merzbacher (Merzbacher 1910). The "connatal" form of Pelizaeus-Merzbacher disease was described later and denotes clinically evident onset within the first few weeks of life and a more severe syndrome (Seitelberger 1954). Seitelberger described a “transitional” form of Pelizaeus-Merzbacher disease that was intermediate in clinical severity between connatal and classical disease (Seitelberger 1970). In 1964, Zeman and colleagues pointed out that Pelizaeus-Merzbacher disease is a dysmyelinating, rather than a demyelinating, entity and stressed the importance of clinical observation and the familial nature of the disorder rather than strict pathological criteria to define the condition (Zeman et al 1964). They also hypothesized that the defect in Pelizaeus-Merzbacher disease affected a myelin proteolipid. Saugier-Veber and colleagues discovered that some families with X-linked spastic paraparesis have PLP1 mutations (Saugier-Veber et al 1994). It must be noted that these syndromes overlap.

Notes on nomenclature. Gene names are italicized, whereas the protein names or abbreviations are not. The PLP1 gene was previously called the PLP1 gene but was renamed after discovery of a similar gene that was named PLP2. The protein is still abbreviated PLP, however. Historically, the numbering of PLP1 amino acids began with the glycine because the initiation methionine is post-translationally excised. The numbering of nucleotides has followed this convention in the past but should now conform to more accepted conventions, with numbering starting at the initiation codon and initiation methionine, as specified by the Human Genome Variation Society.

The content you are trying to view is available only to logged in, current MedLink Neurology subscribers.

If you are a subscriber, please log in.

If you are a former subscriber or have registered before, please log in first and then click select a Service Plan or contact Subscriber Services. Site license users, click the Site License Acces link on the Homepage at an authorized computer.

If you have never registered before, click Learn More about MedLink Neurology  or view available Service Plans.