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The other variants ( types III - VI ) , which have sometimes been categorized as Pelizaeus - Merzbacher disease , may represent mutations in genes encoding other structural myelin proteins or proteins critical to myelination . .
 Pelizaeus - Merzbacher disease
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease 
Text: {0} 
Answer:
 Pelizaeus - Merzbacher disease