ICD-10 Code E88.42 – MERRF Syndrome (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code E88.42 – MERRF syndrome
What it is
E88.42 identifies myoclonic epilepsy with ragged-red fibers, a rare inherited mitochondrial disorder. It affects energy-producing cells and commonly involves the nervous system and muscles.
Clinical signs
Typical features include myoclonus, epilepsy, muscle weakness, and exercise intolerance. Some patients also have ataxia, hearing loss, or other neurologic findings; clinical features vary, so refer to documentation.
When to use this code
Use E88.42 when the provider documents MERRF syndrome or myoclonic epilepsy with ragged-red fibers. Apply it for confirmed diagnoses, genetic or biopsy-supported cases, or clear specialist assessment in the record. Check documentation if the note only says mitochondrial disease.
Do not use for
Do not use this code for nonspecific seizures, isolated myopathy, or other mitochondrial disorders without documented MERRF. If the diagnosis is uncertain, check documentation rather than assuming E88.42.
Coding tip
Code E88.42 only when the record names MERRF or its full equivalent; otherwise, verify the exact mitochondrial diagnosis.