A paraneoplastic syndrome is a syndrome (a set of signs and symptoms) that is the consequence of a tumor in the body (usually a cancerous one). It is specifically due to the production of chemical signaling molecules (such as hormones or cytokines) by tumor cells or by an immune response against the tumor. Unlike a mass effect, it is not due to the local presence of cancer cells. Paraneoplastic syndromes are typical among middle-aged to older people, and they most commonly occur with cancers of the lung, breast, ovaries or lymphatic system (a lymphoma). Sometimes, the symptoms of paraneoplastic syndromes show before the diagnosis of a malignancy, which has been hypothesized to relate to the disease pathogenesis. In this paradigm, tumor cells express tissue-restricted antigens (e.g., neuronal proteins), triggering an anti-tumor immune response which may be partially or, rarely, completely effective in suppressing tumor growth and symptoms. Patients then come to clinical attention when this tumor immune response breaks immune tolerance and begins to attack the normal tissue expressing that (e.g., neuronal) protein. The abbreviation PNS is sometimes used for paraneoplastic syndrome, although it is used more often to refer to the peripheral nervous system.
Signs and symptoms Symptomatic features of paraneoplastic syndrome cultivate in four ways: endocrine, neurological, mucocutaneous, and hematological. The most common presentation is a fever (release of endogenous pyrogens often related to lymphokines or tissue pyrogens), but the overall picture will often include several clinical cases observed which may specifically simulate more common benign conditions.
Endocrine The following diseases manifest by means of endocrine dysfunction: Cushing syndrome, syndrome of inappropriate antidiuretic hormone, hypercalcemia, hypoglycemia, carcinoid syndrome, and hyperaldosteronism.
Neurological The following diseases manifest by means of neurological dysfunction: Lambert–Eaton myasthenic syndrome, paraneoplastic cerebellar degeneration, encephalomyelitis, limbic encephalitis, brainstem encephalitis, opsoclonus myoclonus ataxia syndrome, anti-NMDA receptor encephalitis, and polymyositis.
Mucocutaneous The following diseases manifest by means of mucocutaneous dysfunction: acanthosis nigricans, dermatomyositis, Leser-Trélat sign, necrolytic migratory erythema, Sweet's syndrome, Florid cutaneous papillomatosis, pyoderma gangrenosum, and acquired generalized hypertrichosis. Mucocutaneous dysfunctions of paraneoplastic syndromes can be seen in cases of itching (hypereosinophilia), immune system depression (latent varicella-zoster virus in sensory ganglia), pancreatic tumors (leading to adipose nodular necrosis of subcutaneous tissues), flushes (prostaglandin secretions), and even dermic melanosis (cannot be eliminated via urine and results in grey to black-blueish skin tones).
Hematological The following diseases manifest by means of hematological dysfunction: granulocytosis, polycythemia, Trousseau sign, nonbacterial thrombotic endocarditis, and anemia. Hematological dysfunction of paraneoplastic syndromes can be seen from an increase of erythropoietin (EPO), which may occur in response to hypoxia or ectopic EPO production/altered catabolism. Erythrocytosis is common in regions of the liver, kidney, adrenal glands, lung, thymus, and central nervous system (as well as gynecological tumors and myosarcomas).
Other The following diseases manifest by means of physiological dysfunction besides the categories above: membranous glomerulonephritis, tumor-induced osteomalacia, Stauffer syndrome, Neoplastic fever, and thymoma-associated multiorgan autoimmunity. Rheumatologic (hypertrophic osteoarthropathy), renal (secondary kidney amyloidosis and sedimentation of the immunocomplexes in nephrons), and gastrointestinal (production of molecules that affect the motility and secretory activity of the digestive tract) dysfunctions, for example, may relate to paraneoplastic syndromes.
Mechanism The mechanism for a paraneoplastic syndrome varies from case to case. However, pathophysiological outcomes usually arise when a tumor does. Paraneoplastic syndrome often occurs alongside associated cancers as a result of an activated immune system. In this scenario, the body may produce antibodies to fight off the tumor by directly binding and destroying the tumor cell. Paraneoplastic disorders may arise in that antibodies would cross-react with normal tissues and destroy them.
Diagnosis Diagnostic testing in a possible paraneoplastic syndrome depends on the symptoms and the suspected underlying cancer. Diagnosis may be difficult in patients in whom paraneoplastic antibodies cannot be detected. In the absence of these antibodies, other tests that may be helpful include MRI, PET, lumbar puncture and electrophysiology.
Types
A specifically devastating form of (neurological) paraneoplastic syndromes is a group of disorders classified as paraneoplastic neurological disorders (PNDs). These PNDs affect the central or peripheral nervous system; some are degenerative, though others (such as LEMS) may improve with treatment of the condition or the tumor. Symptoms of PNDs may include difficulty with walking and balance, dizziness, rapid uncontrolled eye movements, difficulty swallowing, loss of muscle tone, loss of fine motor coordination, slurred speech, memory loss, vision problems, sleep disturbances, dementia, seizures, and sensory loss in the limbs. The most common cancers associated with PNDs are breast, ovarian, and lung cancers, but many other cancers can produce paraneoplastic symptoms, as well. The root cause is extremely difficult to identify for paraneoplastic syndrome, as there are so many ways the disease can manifest (which may eventually lead to cancer). Ideas may relate to age-related diseases (unable to handle environmental or physical stress in combination with genetic pre-dispositions), accumulation of damaged biomolecules (damages signaling pathways in various regions of the body), increased oxygen free radicals in the body (alters metabolic processes in various regions of the body), etc. . However, prophylactic efforts include routine checks with physicians (particularly those that specialize in neurology and oncology) especially when a patient notices subtle changes in his or her own body.
Treatment Treatment options include:
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