LEMS is often associated with lung cancer (50–70%), specifically small-cell carcinoma, making LEMS a paraneoplastic syndrome. Of the people with small-cell lung cancer, 1–3% have LEMS. In most of these cases, LEMS is the first symptom of the lung cancer, and it is otherwise asymptomatic. LEMS may also be associated with endocrine diseases, such as hypothyroidism (an underactive thyroid gland) or diabetes mellitus type 1.<unk>  gravis, too, may happen in the presence of tumors (thymoma, a tumor of the thymus in the chest); people with MG without a tumor and people with LEMS without a tumor have similar genetic variations that seem to predispose them to these diseases. HLA-DR3-B8 (an HLA subtype), in particular, seems to predispose to LEMS.
Lambert–Eaton myasthenic syndrome
Botulism
Congenital myasthenic syndrome
Guillain–Barré syndrome
Tension myositis syndrome
De Quervain syndrome
Nemaline myopathy
Inclusion body myositis