Cancer-induced retinal hypersensitivity

What are the earliest indications of cancer? What prompts an apparently healthy person to suspect that 'something may be wrong'? The first manifestations may involve a growing awareness of neuronal dysfunction, such as headaches, dizziness, physical degeneration or vision abnormalities. While denial may extend the time between the patient's appreciation of the health hazard, particularly if the indications are subtle, a sudden decline in vision may be one of the most readily perceived, and provide the strongest stimulation to seek medical help. Cancer-induced neuropathies are rare but provide much information on the genesis of a defined group of autoimmune reactions, and the biological mechanisms involved. The secondary effects of neoplasia, collectively termed paraneoplasia, are often the first indication of cancer. Sudden weight loss is one of the most recognised early signs, and is known to result from biochemical effects on tissues distant from the site of the growth. More recently, immunologic phenomena have been implicated in a series of different paraneoplasia. Examples, such as Lambert-Eaton myasthenic syndrome (LEMS), paraneoplastic cerebellar degenerations (PCD) and cancer-associated retinopathy (CAR) can be identified immunologically through the detection of autoantibody reactions with defined proteins. Interest in the clinical significance of paraneoplastic-associated immunologic reactions increased following the recognition of their strong disease association; PCD patients produce autoantibodies reactive with brain proteins, LEMS patients with muscle components and CAR patients with ocular antigens. Blood tests designed to detect these unusual autoantibody reactions are now in commercial use to identify different forms of paraneoplasia, sometimes before the neoplasm responsible has been identified. The cause of paraneoplasia-related autoimmune reactions has, in some cases, been traced to the patient's cancer, an immunologic connection based upon research findings and published reports of biopsies and cultures that actively express the key proteins involved in cancer-associated organ-specific hypersensitivity.