Mutations in SDHD lead to autosomal recessive encephalomyopathy and isolated mitochondrial complex II deficiency

J Med Genet. 2014 Mar;51(3):170-5. doi: 10.1136/jmedgenet-2013-101932. Epub 2013 Dec 23.

Abstract

Background: Defects of the mitochondrial respiratory chain complex II (succinate dehydrogenase (SDH) complex) are extremely rare. Of the four nuclear encoded proteins composing complex II, only mutations in the 70 kDa flavoprotein (SDHA) and the recently identified complex II assembly factor (SDHAF1) have been found to be causative for mitochondrial respiratory chain diseases. Mutations in the other three subunits (SDHB, SDHC, SDHD) and the second assembly factor (SDHAF2) have so far only been associated with hereditary paragangliomas and phaeochromocytomas. Recessive germline mutations in SDHB have recently been associated with complex II deficiency and leukodystrophy in one patient.

Methods and results: We present the clinical and molecular investigations of the first patient with biochemical evidence of a severe isolated complex II deficiency due to compound heterozygous SDHD gene mutations. The patient presented with early progressive encephalomyopathy due to compound heterozygous p.E69 K and p.*164Lext*3 SDHD mutations. Native polyacrylamide gel electrophoresis and western blotting demonstrated an impaired complex II assembly. Complementation of a patient cell line additionally supported the pathogenicity of the novel identified mutations in SDHD.

Conclusions: This report describes the first case of isolated complex II deficiency due to recessive SDHD germline mutations. We therefore recommend screening for all SDH genes in isolated complex II deficiencies. It further emphasises the importance of appropriate genetic counselling to the family with regard to SDHD mutations and their role in tumorigenesis.

Keywords: SDHD; complex II deficiency; encephalopathy; mitochondrial disorder; succinate dehydrogenase.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Child
  • Electron Transport Complex II / deficiency*
  • Fatal Outcome
  • Female
  • Genes, Recessive / genetics*
  • Humans
  • Metabolism, Inborn Errors*
  • Mitochondrial Diseases*
  • Mitochondrial Encephalomyopathies*
  • Molecular Sequence Data
  • Mutation / genetics*
  • Sequence Alignment
  • Succinate Dehydrogenase / genetics*

Substances

  • Electron Transport Complex II
  • Succinate Dehydrogenase

Supplementary concepts

  • Mitochondrial Complex II Deficiency