Some paraneoplastic syndromes, such as cachexia, leucocytosis, hypercalcaemia and hyperglycaemia, are common. They result from the systemic effects of hormones, or other agents, produced by tumours and/or their metastases. In some cases, dermatological signs may also result from the action of hormones, or other factors, produced by neoplastic cells. Feline paraneoplastic alopecia is one of the feline cutaneous syndromes associated with internal malignancies.
This syndrome has been described in old cats in association with visceral tumours, which include pancreatic adenocarcinoma and bile duct carcinoma, as well as hepatic, splenic and intestinal tumours, with, or without, metastases. The direct relationship between the neoplasm and the cutaneous lesions has been established by resolution of the skin lesions in response to surgical excision of the tumour, and their subsequent recurrence with metastatic disease.
Many cats are presented only once the cutaneous signs have appeared. History soon reveals other non-specific signs that many owners may have attributed to old age. Generally, the condition is non-pruritic in its early stages, but with time and secondary infections the cat may exhibit pruritus.
The cutaneous signs, which usually begin acutely, include a bilaterally symmetrical alopecia, involving the ventrum (Figure 1) and the limbs (Figure 2). As the lesions progress, the skin develops a shiny glistening appearance, together with erythema and some pigmentary macules. The hair is easily epilated. The footpads may also become dry and scaly and can fissure. Generally, affected cats show nonspecific signs such as anorexia, lethargy, vomiting and weight loss, with abdominal pain and distension.
Secondary complications can occur, with concurrent bacterial and Malassezia infections being common. Haematology and biochemical parameters are generally unremarkable, or they may show non-specific signs. The histopathological examination of skin biopsies reveals marked atrophy of the hair follicles and adnexal structures and follicular telogenisation. In addition, the stratum corneum may be thin or absent. The sebaceous glands are generally unaffected. Investigations into where the tumour is located, and the extent of the neoplasia, require ultrasonography and exploratory surgery.
Prognosis is generally poor due to the aggressive nature of the tumour. Surgical excision may prolong the survival time, but the lesions can recur with metastatic disease.
The differential diagnosis for the condition includes secondary bacterial and/or Malassezia dermatitis, iatrogenic or spontaneous hyperadrenocorticism, telogen efﬂuvium, metabolic epidermal necrosis (also known as superficial necrolytic erythema) and demodicosis.
Although the relationship between the tumour and the cutaneous lesions has been established, the pathogenic mechanism for the marked follicular and adnexal atrophy is not known. Cytokines, or other agents, secreted by the neoplastic cells may be responsible for the effect on the hair follicle cycle.
- Usually present with recent history of alopecia
- Usually non-pruritic
- Usually present with easily epilating hair
- Usually have shiny, glistening skin
- Usually patients are older cats with signs of weight loss and intermittent vomiting, which owners attribute to old age
- Has a poor prognosis