A novel Refsum-like disorder that maps to chromosome 20

Neurology. 2009 Jan 6;72(1):20-7. doi: 10.1212/01.wnl.0000333664.90605.23. Epub 2008 Nov 12.

Abstract

Objective: Clinical and genetic characterization of a neurologic disorder resembling Refsum disease in a Norwegian consanguineous family.

Methods: The affected individuals comprise a brother and sister and their third cousin. The family comes from a small island community and genealogic studies showed that both sets of parents are descendants of a man born in 1585. Based on the hypothesis that this is an autosomal recessive disease and that the patients were homozygous for the same mutation (identical by descent), we used homozygosity mapping to define the genetic locus of this disorder.

Results: This slowly progressive disorder starts in childhood with signs of peripheral neuropathy (pes cavus, tendoachilles contracture). Hearing loss and cataract become evident in the third decade. Subsequently, patients develop a disorder of gait due to the combination of ataxia and spasticity, and a pigment retinopathy. While the clinical picture is reminiscent of Refsum disease, affected individuals have normal phytanic and pristanic acid levels in plasma, as well as normal enzymatic activity for alpha-oxidation. We mapped the disease to a 15.96 Mb region on chromosome 20 (20p11.21-q12), containing approximately 200 genes (maximum lod score = 6.3). Sequencing of 23 candidate genes failed to demonstrate detrimental sequence variants.

Conclusions: Our findings show that the clinical syndromes that include Refsum disease are more heterogeneous than previously recognized. We have chosen to report the clinical features and mapping of this novel disorder in the hope that this will permit identification of other families and thus proper genetic characterization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Chromosome Mapping / methods*
  • Chromosomes, Human, Pair 20 / genetics*
  • DNA Mutational Analysis
  • Family Health*
  • Female
  • Genetic Linkage
  • Genotype
  • Humans
  • Iron-Binding Proteins / genetics
  • Male
  • Middle Aged
  • Norway
  • Refsum Disease / genetics*
  • Refsum Disease / physiopathology
  • Trinucleotide Repeat Expansion / genetics

Substances

  • Iron-Binding Proteins
  • frataxin