Paraneoplastic Syndromes

58 Paraneoplastic Syndromes



Astrid Nielssen



1. What is a paraneoplastic syndrome?

Paraneoplastic syndromes are various regional and systemic physiologic, metabolic, and anatomic alterations that arise as a consequence of an underlying neoplastic disease. Examples of some abnormalities that can arise from a malignancy include hypercalcemia, hyperviscosity, hyperhistaminemia, hypoglycemia, inappropriate secretion of antidiuretic hormone, hypertrophic osteopathy, fever, and cachexia. Signs of the paraneoplastic syndrome may be what actually prompt veterinary evaluation in the first place, and not signs directly associated with the tumor itself. Persistence or recurrence of the signs associated with a paraneoplastic syndrome may also be indicative of treatment failure and tumor regrowth.


2. Why is hypercalcemia sometimes identified in the canine cancer patient?

Cancer is the most common cause of hypercalcemia in the dog, and can be seen as a consequence of a wide variety of neoplasms, including most commonly lymphosarcoma. The mechanisms by which tumors produce hypercalcemia are incompletely understood and can vary, but can include increased bone resorption or increased gut and renal calcium absorption caused by production of parathyroid hormone or a parathyroid hormone-like protein (PTHrp), prostaglandins, calcitriol, and osteoclast-activating factor or osteoclast activating factor–like agents. Clinical signs are often associated with the renal effects of hypercalcemia and can include polyuria and polydipsia. Other clinical signs can include inappetence, vomiting, constipation, bradycardia, hypertension, muscle weakness, and neurologic signs including coma and seizures resulting from the effects of the high calcium levels on the gastrointestinal, cardiovascular, and neurologic systems. Treatment is directed at the underlying malignancy and, depending on the severity of the hypercalcemia, supportive treatments aimed at lowering serum calcium levels including saline diuresis, furosemide treatment, and prednisone administration; calcitonin and pamidronate may be indicated.


3. What is hyperviscosity syndrome?

Hyperviscosity syndrome is seen as a result of poor circulation due to increased protein levels or cell concentrations in the blood. Increased protein levels can be seen with neoplasms such as a multiple myeloma. Increased cell concentrations can be seen in such clonal disorders as leukemias and polycythemia vera. Hyperviscosity syndrome can result in an increased cardiac workload and compromised renal function as a result of poor perfusion. Central nervous system (bizarre behavior, seizures), and ophthalmic symptoms (tortuous retinal vessels, retinal hemorrhage, retinal detachment) can also be seen as a result of hypoxia. Hyperglobulinemias can also result in bleeding disorders as a result of the excessive protein levels inhibiting platelet function or functioning as coagulation factor inhibitors. Definitive treatment is directed at the underlying neoplasm. Supportive therapy to decrease viscosity such as parenteral fluid therapy, plasmapheresis and phlebotomy (in cases of polycythemia vera) may also be indicated.

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Jul 31, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on Paraneoplastic Syndromes

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