Lung cancer can cause several types of paraneoplastic syndromes, symptoms that can affect areas of the body distant from the tumor and that are not caused by the direct presence of either the tumor or metastases. Paraneoplastic syndromes can be caused by hormones secreted by the tumor, though the mechanism by which cancers cause these syndromes is often unknown. According to the National Institute of Neurological Disorders and Stroke, symptoms of a paraneoplastic syndrome are often the first sign of a cancer.
Endocrine Syndromes
Lung cancer cells can secrete adrenocorticotrophic hormone, or ACTH, which stimulates the adrenals to secrete cortisol in excess of what the body needs. Symptoms include high blood pressure, elevated blood sugar and redistribution of fat, leading to accumulation of fat in the abdomen and between the scapulas. Secretion of parathyroid hormone by the cancer cells leads to hypercalcemia, or elevated levels of calcium in the blood. Symptoms can include nausea and vomiting, muscle weakness, fatigue and confusion.
Lung cancer can cause SIADH, or syndrome of inappropriate antidiuretic hormone. This can lead to hyponatremia, or low blood sodium, which can cause confusion, seizures and coma.
Clotting Disorders
Migratory thrombophlebitis refers to repeated episodes of clotting and inflammation of veins. According to "Harrison's Principles of Internal Medicine," migratory thrombophlebitis can be the initial symptom of lung cancer. Deep vein thrombosis usually occurs in the legs, causing swelling and pain. Pulmonary embolism occurs when a blood clot detaches from the leg and travels through the bloodstream to block the blood supply to the lungs. Symptoms include shortness of breath, chest pain, anxiety and a rapid heart rate. Left untreated, pulmonary embolism can be fatal.
Neurological Syndromes
Paraneoplastic syndromes can affect any part of the nervous system. When the cortex is affected, symptoms can include seizures, memory loss, confusion, agitation and dementia. Spinal-cord involvement can cause muscle rigidity and paralysis. According to "Harrison's Principles of Internal Medicine," involvement of the brain center that controls respiration and of the nerves that control the heart, is a frequent cause of death in patients with paraneoplastic neurological disease.
Lambert-Eaton myasthenic syndrome, or LEMS, a disease similar to mysathenia gravis, is another syndrome caused by lung cancer. In LEMS, transmission between nerves and muscles is disrupted, leading to symptoms that include weakness, double vision, drooping of the eyelids, dry mouth and impotence.
References
- National Institute of Neurological Disorders and Stroke: Paraneoplastic Syndromes
- Mayo Clinic: Hypercalcemia
- "Harrison's Principles of Internal Medicine, 17th Edition"; Antoni Fauci (ed); 2008
