Myasthenic syndromes in diseases classified elsewhere

This code represents myasthenic syndromes that are secondary manifestations of other underlying diseases, rather than primary autoimmune myasthenia gravis. These syndromes involve impaired neuromuscular transmission, leading to muscle weakness and fatigue, but are directly attributable to another classified condition.

Use this code when documentation clearly links myasthenic symptoms to an underlying systemic disease, such as certain cancers (e.g., Lambert-Eaton myasthenic syndrome associated with small cell lung cancer), autoimmune disorders, or drug-induced conditions. The primary underlying disease must also be coded.

• Always code the underlying disease first, followed by this code to indicate the myasthenic syndrome as a manifestation.
• Distinguish carefully from primary autoimmune myasthenia gravis (358.0), which is not secondary to another condition.
• Ensure documentation specifies the "myasthenic syndrome" and its association with a "disease classified elsewhere."