ICD-10-CM 2027
ICD-10 code for Myasthenic syndrome
From the official ICD-10-CM alphabetic index entry “Syndrome › myasthenic”. Page updated September 29, 2026.
About coding Myasthenic syndrome
The ICD-10-CM code for Myasthenic syndrome is G70.9 (Myoneural disorder, unspecified). The official index lists 4 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on G70.9.
Within G70, choose G70.9 (Myoneural disorder, unspecified) only when documentation doesn't support a more specific option: myasthenia gravis (G70.0), toxic myoneural disorders (G70.1), congenital and developmental myasthenia (G70.2) and other specified myoneural disorders (G70.8).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 073 (Cranial and Peripheral Nerve Disorders with MCC, relative weight 1.5779) and DRG 074 (Cranial and Peripheral Nerve Disorders without MCC, relative weight 1.0173), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific Myasthenic syndrome codes (official index)
- in
- diabetes mellitus
- endocrine disease NEC E34.9 — Endocrine disorder, unspecified
- neoplastic disease D49.9 — Neoplasm of unspecified behavior of unspecified site
- thyrotoxicosis (hyperthyroidism) E05.90 — Thyrotoxicosis, unspecified without thyrotoxic crisis or storm
- with thyroid storm E05.91 — Thyrotoxicosis, unspecified with thyrotoxic crisis or storm
Common questions about Myasthenic syndrome ICD-10 codes
What is the ICD-10 code for Myasthenic syndrome?
- G70.9 — Myoneural disorder, unspecified. More specific codes apply when the documentation supports them: E34.9, D49.9, E05.90, E05.91.
Is G70.9 billable?
- Yes. G70.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can G70.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict G70.9 as a principal diagnosis.
Is G70.9 a CC or MCC?
- No. G70.9 is neither a CC nor an MCC under MS-DRG v44.0.