Disorders of peroxisome assembly and function

Kimberly A Chapman MD PhD (

Dr. Chapman of George Washington University and Children’s National Rare Disease Institute has no relevant financial relationships to disclose.

)
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 Sanofi Genzyme.)
Originally released December 28, 1993; last updated March 11, 2019; expires March 11, 2022

This article includes discussion of disorders of peroxisome assembly and function, disorders of peroxisome assembly, peroxisomal polyenzymopathies, group 1 peroxisomal disorders, disorders of peroxisome biogenesis, generalized peroxisomal disorders, disorders of peroxisome assembly, Zellweger syndrome, cerebrohepatorenal syndrome, neonatal adrenoleukodystrophy, rhizomelic chondrodysplasia punctate, and X-linked adrenoleukodystrophy. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

The peroxisome biogenesis disorders are a heterogeneous group of rare autosomal recessive diseases. The underlying defect is the failure to form functional peroxisomes, resulting in deficiencies of multiple enzymes targeted to this organelle and progressive, multisystem diseases. Two clinical categories of disease are distinguished, Zellweger spectrum and rhizomelic chondrodysplasia punctata spectrum. The author describes the 2 clinical spectra of peroxisome assembly defects and highlights the marked strides in understanding the molecular pathology. In addition, the author reviews some commonly confused single enzyme peroxisomal disorders.

Key points

 

Peroxisomal assembly and biogenesis disorder can present with:

 

• Neuronal abnormalities (ie, migration defects and germinal cysts, polyneuropathy, ataxia, and leukodystrophy)

 

• Retinal abnormalities (ie, dystrophy) and hearing loss (sensorineural)

 

• Bone formation abnormalities

 

• Liver dysfunction

 

• Nonfamilial features (including high forehead, epicanthal folds, micrognathia, very large fontanelles, and shallow supraorbital ridges)

 

• Age of onset often corresponds with severity.

Historical note and terminology

Peroxisomes are single-layer lipid biolayer organelles found in the cytosol that play a role in beta oxidation and reduction of reactive oxygen species, among other things, by their ability to contain oxidases and catalase.

Microbodies were first described in mouse kidney by Rhodin in 1958 and these purified microbodies from rat liver were then found to be active in peroxide-linked oxidation reactions, leading to the name "peroxisomes" (Lazarow and Moser 1995). The ubiquitous presence of these single-membraned organelles, their role in fatty acid oxidation, and their absence in patients with Zellweger syndrome (Goldfischer et al 1973) stimulated interest in peroxisome biology. A reliable assay for peroxisome dysfunction based on elevated serum very long-chain fatty acids defined a new category of human metabolic disease (Moser et al 1999).

The failure to assemble normal peroxisomes and the impaired ability to import peroxisome matrix proteins result in multiple deficiencies of peroxisomal enzymes (peroxisome biogenesis and assembly disorder). Disorders of peroxisome assembly can be divided into 2 classes: the Zellweger syndrome spectrum and rhizomelic chondrodysplasia punctata. The peroxisome biogenesis disorders may affect the brain, retina, craniofacies, kidney, and skeleton (Zellweger 1987; Brown et al 1993; Lazarow and Moser 1995).

Zellweger spectrum is defined by the clinical disorders of Zellweger syndrome, neonatal adrenoleukodystrophy, and infantile Refsum disease, and is characterized as severe, intermediate, and mild. These disorders were described before the relationship to peroxisome deficiency was known and thus the terms do not relate directly to the underlying gene defect.

The genes associated to these disorders are referred to as the PEX genes. In order to determine the genes involved in the peroxisome biogenesis disorders, patient fibroblast cell lines were collected and fused for biochemical complementation. This approach defined at least 13 complementation groups, each predicted to represent a different gene defect (Moser et al 1995). Many PEX genes were subsequently identified by screening human cDNA libraries (Dodt et al 1996). PEX genes encode proteins referred to as peroxins. In sum, 12 PEX genes are associated with Zellweger spectrum disorders (ranging from mild to severe in phenotype) (Steinberg et al 2004; Steinberg et al 2019). In contrast, rhizomelic chondrodysplasia type 1 is associated exclusively with a defect in the PEX7 gene (Braverman et al 1997).

A variety of historic labels have been ascribed to the Zellweger spectrum (cerebrohepatorenal syndrome, hyperpipecolic acidemia). In addition, some patients initially diagnosed with Usher syndrome or Leber congenital amaurosis due to their physical characteristics but were later shown to have assembly defects (Ek et al 1986; Raas-Rothschild et al 2002). Others have been diagnosed with Krabbe disease, spinal muscular atrophy type 1 (Baumgartner 1998), or Prader-Willi syndrome due to their severe hypotonia and were found to have peroxisomal disorders. Still others were initially thought to have Down syndrome based on facial features and decreased tone until normal karyotype was obtained and further testing done.

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