Pelizaeus-Merzbacher spectrum disorder null syndrome UMLS:C5439441 Orphanet:280234 MEDGEN:1740046 Pelizaeus-Merzbacher disease, null syndrome GARD:0017292 The null syndrome is part of the Pelizaeus-Merzbacher disease (PMD) spectrum and is characterized by mild PMD features associated with demyelinating peripheral neuropathy. PLP1 null syndrome icd11.foundation:1663254692 MONDO:0017225