What Are Paraneoplastic Syndromes?
Paraneoplastic syndromes are a group of rare conditions that occur in people with cancer. They’re characterized by clinical manifestations that aren’t dependent on the local or systemic effects of the malignant tumor or its metastasis.
These syndromes can affect all the systems of the human body, so the different signs and symptoms will depend on the organ affected. They’re part of any type of cancer, but are more frequently associated with lung, breast, ovarian, uterine, and blood cancers.
In some cases, they’re detected prior to the diagnosis of the malignant tumor or during its evolution. It’s estimated that about 8% of cancer patients suffer from them.
What causes paraneoplastic syndromes?
Paraneoplastic syndromes aren’t related to local invasion or compression by the malignant tumor. Nor are they caused by the presence of metastases.
They are thought to be caused by an abnormal production of substances that will depend on the primary malignant tumor or by a cross-reaction between healthy tissue and tumor tissue. This cross-reaction causes an erroneous immune system response against non-diseased organs.
These substances behind paraneoplastic syndromes may be hormones, growth factors, antibodies, peptides, or cytokines.
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Classification of paraneoplastic syndromes
The clinical manifestations of paraneoplastic syndromes will depend on the human body system affected. The focus may be on the endocrine system, skin, blood, nervous system, or joints. There may also be kidney involvement.
There are systemic or general clinical manifestations given by fever, night sweats, lack of appetite and significant weight loss. They aren’t linked to any one system, but come from the release of agents associated with the exacerbated inflammatory or immune response.
The glandular system is affected in paraneoplastic syndromes by the production of biologically active substances. Among the most notorious and recurrent signs are the following:
- Cushing’s syndrome (due to hypercortisolism caused by increased ACTH). In this case, there’s excess cortisol that causes increased blood glucose, decreased potassium, high blood pressure, central obesity, and a puffy face.
- Inappropriate secretion of antidiuretic hormone. Causes low sodium levels and manifests with headaches, weakness, memory impairment, seizures, and even a coma.
- Increased calcium (hypercalcemia). It has a high mortality, up to 50%. It’s the product of several mechanisms, mainly linked to the secretion of parathyroid hormone by tumor cells.
- Carcinoid syndrome. Due to the release of serotonin, histamine, catecholamines, prostaglandins, and vasoactive peptides. Causes head and neck edema, abdominal pain, diarrhea, bronchospasm, facial erythema, wheezing, and heart and lung failure.
- Hypersecretion of various hormones, such as prolactin, gonadotrophin and calcitonin.
- Alterations in water and electrolyte balance. Secondary to hormone production or diarrhea caused by the secretion of biologically active substances.
- Arterial hypertension. Due to abnormal secretion of adrenaline and noradrenaline or due to excess cortisol.
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On the skin, the signs are both varied and numerous. Among the most common are pruritus (itching) and erythroderma (reddening of the skin and mucous membranes). Both are the result of hypereosinophilia, mastocytosis, and the presence of biologically active substances.
In addition, pigmented or keratotic lesions are often present, such as the acanthosis nigricans (dark, velvety areas in folds), generalized dermal melanosis (due to melanocyte proliferation), and seborrheic keratoses (spots with serous discharge).
Blood problems due to paraneoplastic syndromes are usually diagnosed after the identification of the malignant tumor. They involve a wide range of manifestations, including the following:
- Chronic anemia associated with cancer and hemolytic anemia
- Red cell aplasia
- Disseminated intravascular coagulation
- Venous thrombosis
Neurological signs are the product of immune system activity on neural tissue. Depending on the organ affected, symptoms can range from cognitive and personality disturbances to difficulty with motor coordination.
In cases of neurological paraneoplastic syndromes, they usually account for up to 70% of the first manifestations of a tumor.
In some cases, there’s the involvement of the central nervous system due to diffuse inflammation (called encephalomyelitis). Peripheral nerves are also involved and may cause Guillain-Barré syndrome.
Autonomic nervous system involvement is evidenced by positional hypotension, neurogenic bladder, esophageal and intestinal movement disorders and cardiac arrhythmias. There may also be manifestations of myopathy, spontaneous eye movements, and myasthenia gravis.
Joints are rarely affected in paraneoplastic syndromes. There may be arthritis, periostitis, fasciitis, osteomalacia, migratory polyarthritis, or the presence of painful joint swellings (hypertrophic osteoarthropathy).
Treatment and prognosis of paraneoplastic syndromes
There’s no specific treatment for these syndromes, because they depend on the system involved. It must begin with control of the underlying cancer and, in some cases, drugs to suppress immune action are required.
Paraneoplastic syndromes are very varied. In many cases, they’re the first clinical manifestation of the tumor, so their timely diagnosis leads to the identification of the underlying malignant process.It might interest you...