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Background:
Cytochrome C Oxidase deficiency is a rare inherited metabolic disorder characterized by deficiency of the enzyme cytochrome C oxidase,an essential enzyme that is active in the oxidative phosphorylation.It is clinically heterogeneous, ranging from isolated myopathy to severe multisystem presentation.Acute disseminated encephalomyelitis(ADEM) is a monophasic polysymptomatic inflammatory condition of the CNS that principally involves the white matter although the grey matter may also be affected.

Case report:

A 6 years old boy, product of a consanguineous marriage with history of progressive weakness and convulsions noted at 2 years of age in his sister who died at the age of 5 years with no definite diagnosis.At the age of 2 years, he presented with fever, encephalopathy, and seizures, proceeded by varicella skin infection. Diagnosed as ADEM based on MRI.He showed slow recovery but remain with poor speech, and ataxic gait. At 4 years of age he developed the 2^nd episode of ADEM, admitted in coma state and ventilated for 10 weeks. Progressive neurologic decline, and frequent myoclonic seizures were noted despite full support with immunosuppressive therapy, antiviral treatment, antiepileptic drugs, and megavitamins.MRI showed generalized cortical swelling and abnormal high signal intensity diffusely involving cerebral cortex, cerebellum,and deeper gray matter.He remained in vegetative state with spastic quadriplegia.Muscle biopsy showed reduction of cytochrome C oxidase activity and abnormal accumulation of mitochondria at subsarcolemmal membrane.

Conclusion:
This case serves as a reminder of the clinical heterogeneity of cytochrome C oxidase deficiency,and physician should consider a broader differential diagnosis for ADEM.

Cytochrome C oxidase deficiency, Complex IV, Mitochondrial disorders, acute disseminated encephalomyelitis, MRI, Children.