Sarah Leigh edited their review of gene: PEX6: Added comment: Arthrogryposis maybe over looked in patients with Peroxisome biogenesis disorder 4A (Zellweger) (OMIM:614862) and Peroxisome biogenesis disorder 4B (OMIM:6148630), as these conditions are characterized by a severe phenotype and premature death in some cases. If this is the case, for Peroxisome biogenesis disorder 4B (OMIM:614863), Falkenberg et al (PMID: 29220678) have identified Allelic Expression Imbalance (AEI) as a mechanism responsible for the condition. Affected patients (7 unrelated cases) were monoallelic for rs61753230 (c.2578C>T, p.Arg860Trp) and rs144286892 (c.∗442_445 delTAAA), with these variants being on the same chromosome (cis). It would appear that rs144286892 causes the over expression of the allele that it is on, resulting in over expression of rs61753230. The unaffected parents analysed were monoallelic for rs61753230 and biallelic for rs144286892, resulting in overexpression of both rs61753230 and wild type alleles (PMID: 29220678). Experimental evidence revealed that rs61753230 has a dominant-negative effect on the function of the PEX1- PEX6 complex in peroxisomal matrix protein import (PMID: 29220678).; Changed mode of pathogenicity: Other; Changed mode of inheritance: BOTH monoallelic and biallelic, autosomal or pseudoautosomal