Complex II deficiency-A case report and review of the literature

Shailly Jain-Ghai*, Jessie M. Cameron, Almundher Al Maawali, Susan Blaser, Nevena Mackay, Brian Robinson, Julian Raiman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

64 Citations (Scopus)


Complex II deficiency is a rare cause of mitochondrial respiratory chain defects with a prevalence of 2-23%. It is exclusively nuclear encoded and functions in the citric acid cycle by oxidizing succinate to fumarate and in the mitochondrial electron transport chain (ETC) by transferring electrons to ubiquinone. Of the four subunits, SDHA and SDHB are catalytic and SDHC and SDHD are anchoring. Mutations in SDHA and SDHAF1 (assembly factor) have been found in patients with CII deficiency and a mitochondrial phenotype. We present a patient with CII deficiency with a previously undescribed phenotype of dilated cardiomyopathy, left ventricular noncompaction, failure to thrive, hypotonia, and developmental delay. Also, a comprehensive review of 36 cases published in the literature was undertaken. The results show that CII deficiency has a variable phenotype with no correlation with residual complex activity in muscle although the phenotype and enzyme activities are comparable within a family. For some, the condition was fatal in infancy, others had multisystem involvement and some had onset in adulthood with mild symptoms and normal cognition. Neurological involvement is most commonly observed and brain imaging commonly shows leukoencephalopathy, Leigh syndrome, or cerebellar atrophy. Mutations in SDHAF1 are associated with leukoencephalopathy. Other organ systems like heart, muscle, and eyes are only involved in about 50% of the cases but cardiomyopathy is associated with high mortality and morbidity. In some patients, riboflavin has provided clinical improvement.

Original languageEnglish
Pages (from-to)285-294
Number of pages10
JournalAmerican Journal of Medical Genetics, Part A
Issue number2
Publication statusPublished - Feb 2013
Externally publishedYes


  • Complex II
  • Mitochondrial disorder
  • SDHA
  • SDHAF1
  • Succinate dehydrogenase

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)


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