Paraneoplastic disorders
From Felipedia
Paraneoplastic syndromes (PNS) are non-metastatic complications of cancer in cats. They can affect all parts of the body, including the skin, bone, muscle, immune system, individual organs and nervous system and are thought to be immunologically mediated and are unrelated to metabolic or nutritional disorders, infection, stroke, or complications of therapy (eg, chemotherapy).
Although the exact pathogenesis is unclear, similarities between antigens expressed by tumours and neural tissues may lead to effects against neural tissue by immune cells targeting the tumour[1].
Contents |
Clinical signs
- Paraneoplastic syndromes affecting the CNS are rare in animals, but lack of awareness may have led to a low detection rate. Clinical signs suggest of neuropathies may allude to primary pulmonary or hepatic neoplasia. Paraneoplastic myasthenia gravis (MG) has been reported in dogs, but not as yet in cats.
- Humoral hypercalcemia of malignancy (HHM). This is rare in cats (compared with dogs) and is often caused by carcinomas. Neoplastic tissue secretes parathyroid hormone-related protein (PTHrP), resulting in hypercalcemia due to osteoclastic bone resorption and renal tubular reabsorption of calcium. HHM rarely causes clinical signs.
- Paraneoplastic dermatoses associated with metastatic tumors (e.g. bile duct carcinoma, thymoma, pheochromocytoma, mammary adenocarcinoma, pulmonary adenocarcinoma). Often present as paraneoplastic alopecia; symmetrical, non-pruritic hair loss, often ventral abdominal regions.
- Hyperviscosity syndrome secondary to lymphosarcoma.
- Skin diseases
- - Acquired cutaneous hyperfragility syndrome, sometimes associated with hyperadrenocorticism, usually caused by benign pituitary adenomas. Can also be idiopathic in origin. These cases often present with hyperelasticity and easily torn skin, Other signs are often present such as PU/PD, concurrent diabetes mellitus and lethargy.
- - Pancreatic paraneoplastic alopecia
- - Paraneoplastic exfoliative dermatitis
- - Superficial necrolytic dermatitis
The pathogenesis of paraneoplastic neuropathies is uncertain, although some forms may be related to molecular mimicry[2].
Diagnosis
Diagnosis of paraneoplastic syndromes is a combination of many factors; older cats (over 10 years usually), clinical history alluding to vague symptoms of weight loss, inappetance etc. Progressive alopecia, distal tumors suggestive of primary neoplasia elsewhere.
Blood results, chest Xrays and full physical examination often suggest concurrent neoplasia in these cases. In paraneoplastic syndromes, a normochromic, normocytic, non-regenerative anemia is commonly found, presumably as a consequence of neoplastic myelophthisis.
Treatment
Prognosis in most cats is poor due to age-related non-responsiveness to chemotherapy. Palliative therapy is usually indicated.
