Small cell lung cancer with peripheral neuropathy as the first symptom: Two case reports.

Background: Small cell lung cancer (SCLC) is the most malignant type of lung cancer. Even in the latent period and early stage of the tumor, SCLC is prone to produce distant metastases with complex and diverse clinical manifestations. SCLC is most closely related to paraneoplastic syndrome, and some cases present as paraneoplastic peripheral neuropathy (PPN). PPN in SCLC appears early, lacks specificity, and often occurs before diagnosis of the primary tumor. It is easy to be misdiagnosed as a primary disease of the nervous system, leading to missed diagnosis and delayed diagnosis and treatment.

Case summary: This paper reports two cases of SCLC with limb weakness as the first symptom. The first symptoms of one patient were rash, limb weakness, and abnormal electromyography. The patient was repeatedly referred to the hospital for limb weakness and rash for > 1 year, during which time, treatment with hormones and immunosuppressants did not lead to significant improvement, and the condition gradually aggravated. The patient was later diagnosed with SCLC, and the dyskinesia did not worsen as the dermatomyositis improved after antineoplastic and hormone therapy. The second case presented with limb numbness and weakness as the first symptom, but the patient did not pay attention to it. Later, the patient was diagnosed with SCLC after facial edema caused by tumor thrombus invading the vein. However, he was diagnosed with extensive SCLC and died 1 year after diagnosis.

Conclusion: The two cases had PPN and abnormal electromyography, highlighting its correlation with early clinical indicators of SCLC.