Mononeuropathy multiplex as a first manifestation of renal cell carcinoma: a case report

The neurologic symptoms that appear due to paraneoplastic syndrome may give manifestations of undiagnosed tumor, and give an opportunity for early detection and treatment of it. CASE PRESENTATION: Here the authors present a case of a 54-year-old woman who suffered from rapidly progressive muscle weakness, accompanied by right third cranial nerve palsy. CLINICAL DISCUSSION: The nerve conduction study consistent with multiple mononeuropathy, and laboratories revealed undiagnosed diabetes mellitus but elevated erythrocyte sedimentation rate and the rapid progression prompted for additional investigations. Brain MRI, repetitive nerve stimulation, lumbar puncture, and paraneoplastic panel were all negative. Computed tomography scan with contrast for the abdomen showed a right renal mass consistent with renal cell carcinoma. The tumor was removed and steroids and intravenous immunoglobulin was started but without any clinical improvement because of the late presentation. CONCLUSION: Patients with renal cell carcinoma can present with paraneoplastic syndromes but multiple mononeuropathy are extremely rare. It is crucial to investigate for all possible causes of neuropathy and not attributing it to a new discovered diabetes in the presence of clinical and laboratory red flags such as rapid progression and elevated erythrocyte sedimentation rate.