Lambert-Eaton syndrome in disease classified elsewhere

This code represents Lambert-Eaton Myasthenic Syndrome (LEMS) when it is a secondary manifestation of a non-neoplastic underlying disease. LEMS is an autoimmune disorder characterized by muscle weakness due to impaired acetylcholine release at the neuromuscular junction. This specific code is used when the primary condition causing LEMS is not cancer.

Use this code when documentation clearly indicates LEMS as a paraneoplastic syndrome associated with a non-cancerous condition, such as another autoimmune disease. This code is appropriate when the physician explicitly states "Lambert-Eaton syndrome in disease classified elsewhere" or similar phrasing, linking LEMS to a non-malignant primary diagnosis.

• Always sequence the underlying non-neoplastic disease first, followed by this code.
• Carefully review documentation to differentiate between LEMS associated with cancer (G73.1) and LEMS associated with other diseases.
• Do not code with G73.1 (Lambert-Eaton syndrome in neoplastic disease) as per Excludes1 note.