G73.3Myasthenic syndromes in other diseases classified elsewhere

G73.3 is the ICD-10-CM diagnosis code for Myasthenic syndromes in other diseases classified elsewhere. It belongs to category G73 (disorders of myoneural junction and muscle in diseases classified elsewhere), block G70-G73 (diseases of myoneural junction and muscle) and chapter 6 (diseases of the nervous system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within G73, choose G73.3 (Myasthenic syndromes in other diseases classified elsewhere) only when documentation doesn't support a more specific option: Lambert-Eaton syndrome in neoplastic disease (G73.1) and myopathy in diseases classified elsewhere (G73.7).

Code first underlying disease, such as: neoplasm (C00-D49) and thyrotoxicosis (E05.-).

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 056 (Degenerative Nervous System Disorders with MCC, relative weight 2.2655) and DRG 057 (Degenerative Nervous System Disorders without MCC, relative weight 1.2838), 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.

It is a manifestation code, so it describes the effect of an underlying disease and can't be the principal diagnosis. Code the underlying condition first.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 358.1 (Myasthenic syndromes in diseases classified elsewhere).