Succinate dehydrogenase A deficiency
SDHA deficiency

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Description from OMIM

Mitochondrial complex II deficiency is an autosomal recessive disorder with a highly variable phenotype. Some patients have multisystem involvement of the brain, heart, muscle, liver, and kidneys resulting in death in infancy, whereas others have only isolated cardiac or muscle involvement with onset in adulthood and normal cognition. Measurement of complex II activity in muscle is the most reliable means of diagnosis; however, there is no clear correlation between residual complex II activity and severity or clinical outcome. In some cases, treatment with riboflavin may have clinical benefit (summary by Jain-Ghai et al., 2013).



Prevalence of clinical parameters (%)







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Number of patients in the reference Percent affected patients (Between 0 and 1, eg. 0.1 = 10%)
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List of symptoms



Symptom/sign Organ system Percent affected Pubmed id Added on(yyyy-mm-dd) Edit/add reference
Spasticity nervous 100 % 19465911 2013-04-11
Leukodystrophy nervous 100 % 19465911 2013-04-11
Succinate accumulation nervous 100 % 19465911 2013-04-11
Dystonia nervous 100 % 19465911 2013-04-11
Short stature multi 71 % 19465911 2013-04-11
Developmental delay nervous 50 % 23322652 2013-04-12
Hypotonia nervous 50 % 23322652 2013-04-12
Myopathy skeletal 40 % 23322652 2013-04-12
Optic atrophy nervous 40 % 23322652 2013-04-12
Ataxia nervous 38 % 23322652 2013-04-12
Developmental delay nervous 29 % 19465911 2013-04-11
Lactate accumulation nervous 17 % 19465911 2013-04-11
Hearing loss nervous 14 % 19465911 2013-04-11
Vomiting digestive 14 % 19465911 2013-04-11
Cerebellar atrophy nervous 14 % 23322652 2013-04-12



List of references:


SDHAF1, encoding a LYR complex-II specific assembly factor, is mutated in SDH-defective infantile leukoencephalopathy.
Daniele Ghezzi, Paola Goffrini, Graziella Uziel, Rita Horvath, Thomas Klopstock, Hanns Lochm├╝ller, Pio D'Adamo, Paolo Gasparini, Tim M Strom, Holger Prokisch, Federica Invernizzi, Ileana Ferrero, Massimo Zeviani,

We report mutations in SDHAF1, encoding a new LYR-motif protein, in infantile leukoencephalopathy with defective succinate dehydrogenase (SDH, complex II). Disruption of the yeast homolog or expression of variants corresponding to human mutants caused SDH deficiency and failure of OXPHOS-dependent growth, whereas SDH activity and amount were restored in mutant fibroblasts proportionally with re-expression of the wild-type gene. SDHAF1 is the first bona fide SDH assembly factor reported in any organism.

Nature genetics - Jun 2009



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,

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.

American journal of medical genetics. Part A - Feb 2013