The peroxisome biogenesis disorders (PBDs) neonatal adrenoleukodystrophy (NALD) and infantile Refsum disease (IRD) represent the milder manifestations of the ZELLWEGER SYNDROME SPECTRUM. Most patients survive to adolesence and affected children experience HYPOTONIA but are able to achieve developmental milestones. In addition, craniofacial features are similar to but less pronounced than in Zellweger syndrome. Patients also may experience SEIZURES. and have renal cysts. In contrast to ZS, they may also develop SENSORINEURAL HEARING LOSS and RETINITIS PIGMENTOSA. Caused by mutations in the PEX genes. OMIM: 601539
