However, atypical clinical features were present in some patients, including normal liver function and Leigh syndrome (subacute necrotizing encephalomyelopathy) seen in association with TRMU mutations and no cardiomyopathy with founder SCO2 mutations.
We report two novel pathogenic SURF1 mutations in a patient with Leigh syndrome and one novel SCO2 mutation in a patient with hypertrophic cardiomyopathy.
Mutations have, however, been identified in several COX assembly factors: SURF1 (Leigh Syndrome), SCO2 (hypertrophic cardiomyopathy), SCO1 (hepatic failure, ketoacidotic coma), and COX10 (encephalopathy, tubulopathy).
All of the patients with mutations in SURF-1 had Leigh syndrome, whereas the 3 patients with SCO2 mutations had a combination of encephalopathy and hypertrophic cardiomyopathy, and the neuropathology did not show the typical features of Leigh syndrome.
The clinical phenotype caused by mutations in human SCO2 differs from that caused by mutations in SURF1, the only other known COX assembly gene associated with a human disease, Leigh syndrome.