A rare case of long-term paraesthesia diagnosed as a paraneoplastic syndrome by anti-SOX1 antibody determination

Abstract

Paraneoplastic syndromes (PS) are a rare presentation of cancer, most commonly associated with small cell lung cancer (SCLC), breast cancer and haematologic malignancies. The diagnosis of PS is challenging because it could affect multiple organ systems and it may present before the tumour is visible by imaging. We report a malignant tumour diagnosed in a male patient who referred long-term paraesthesia and proximal muscle strength loss. After ruling out common causes of polyneuropathy, the anti-SOX1 antibody gave light to the diagnosis. A pulmonary opacity in the upper right lobe was observed in the chest X-ray and a pulmonary tumour was later confirmed by CT scan. The biopsy of the cervical lymphadenopathy determined an SCLC, which caused a PS called Lambert-Eaton myasthenic syndrome (LEMS). Our case raises awareness of a rare PS presentation, which can be diagnosed by specific antibodies, allowing early diagnosis and treatment of lung cancer.

Keywords: immunology; lung cancer (oncology); neurooncology; oncology.

Figure 1

Chest X-ray at diagnosis. Posteroanterior projection (A) and lateral projection (B).

Figure 2

CT shows the 45 mm lymphadenopathy in the axial view (A) and the pulmonary tumour in the right upper lobe of the coronal view (B).

Figure 3

CT scan shows the lymphadenopathy surrounding the right pulmonary artery in the coronal view (A) and the sagittal view shows the compression of the superior vena cava by the pulmonary tumour (B).

Figure 4

Electromyography displays a post-maximum voluntary contraction facilitation (A), a null sympathetic skin response (B) and a decremented response to slow repetitive stimuli 3 Hz (C). Arrows indicate the pathological response to stimuli.