DGUOK

Mitochondrial DNA Depletion Syndrome 3

Clinical Characteristics
Ocular Features: 

Nystagmus, disconjugate eye movements, and "optic dysplasia" have been noted.

Systemic Features: 

Infants feed poorly which is frequently associated with vomiting, failure to thrive, and growth delay.  They are hypothermic, hypoglycemic, and often jaundiced with signs of liver failure noted between birth and 6 months of age and death by approximately 1 year of age.  Hepatosplenomegaly is present early with abnormal liver enzymes, cholestasis, steatosis, and hepatocellular loss followed by cirrhosis with portal hypertension.  Metabolic acidosis, hyperbilirubinemia, hypoalbuminemia, and hypoglycemia are often present.  Mitochondrial DNA depletion in the liver approaches 84-90%.

All patients have encephalopathic signs with evidence of cerebral atrophy, microcephaly, hypotonia.  Hyperreflexia may be present and some infants have seizures.  Muscle tissue, however, has normal histology and respiratory chain activity.

Genetics

This disorder results from homozygous or compound heterozygous mutations in the DGUOK gene (2p13).

The same gene is mutated in PEOB4 (617070).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

There is no effective treatment.  Liver transplantation in one infant was unsuccessful.  

References
Article Title: 

External Ophthalmoplegia, Progressive, with mtDNA Deletions, AR 4

Clinical Characteristics
Ocular Features: 

Patients have adult onset (6th to 7th decade of life) and progressive ptosis and external ophthalmoplegia of variable severity.

Systemic Features: 

There is a great deal of clinical heterogeneity in this condition.  Some patients have adult onset proximal and limb girdle progressive muscle weakness.  Other individuals complain of exercise-induced muscle pain and increased weakness.  Dysphagia and dysphagia may be present.  More widespread signs such as peripheral neuropathy, hearing impairment, cortical atrophy, and liver disease are variably present.  

Genetics

Compound heterozygous mutations in the DGUOK (deoxyguanosine kinase) gene (2p13) have been identified in this disorder.  Multiple deletions in the mitochondrial DNA of skeletal muscle have been found as well.    

Biallelic mutations in the DGUOK gene also cause more widespread disease as evidenced in the mitochondrial DNA depletion syndrome MTDPS3 (251880). 

A similar condition, External Ophthalmoplegia, Progressive, with mtDNA Deletions, AR 3, (617069) is caused by mutations in the TK2 gene.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Ptosis surgery may be of benefit.

References
Article Title: 
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