Feline Symmetrical Alopecia

Chapter 52 Feline Symmetrical Alopecia

Alopecia is defined as the absence of hair from skin areas where it is normally present. Feline symmetric alopecia (FSA) is a cutaneous reaction pattern with many possible etiologies; FSA should not be a final diagnosis, and it is important to determine the primary cause for the most appropriate therapy to be instituted.

In order to properly define the clinical problem and formulate an appropriate list of differential diagnosis, it is helpful to further categorize alopecia as follows:

Alopecia in the cat, whether symmetric or asymmetric, is most often associated with varying degrees of pruritus and skin reactivity depending on the underlying disease.


Multiple factors play a role in normal hair follicle development and growth (Table 52-1). Absence or changes in one or more of the factors can alter the normal hair growth process and result in alopecia. The underlying causes of FSA can vary depending on the area or region of the body affected. This chapter focuses on the causes of FSA that are primarily confined to the trunk (dorsum, perineum, caudal thighs, flanks, ventral abdomen, and thorax). The underlying causes of FSA affecting the trunk region have been classified into those that are associated with self-trauma or pruritus (e.g., licking or scratching) and those that are nonpruritic (Table 52-2).


Internal Factors External Factors
Genetic Nutritional
Hormonal Infectious
Immunologic Bacterial
Neoplastic Fungal (dermatophytes)
Stress Parasitic
Physical (traumatic)
Chemical (toxins, drug therapy)

Self-induced (Pruritic) Alopecia

Allergic dermatitis and parasitic infestations are the most common causes of self-induced alopecia. Other cutaneous reaction patterns associated with allergic and parasitic dermatoses are feline miliary dermatitis (see Chapter 53) and eosinophilic granuloma complex lesions (see Chapter 53). Allergic causes of self-induced alopecia in cats typically do not have as strong a regional distribution (i.e., involvement of specific body locations) as is the case in dogs.

Non–self-induced (Nonpruritic) Alopecia

Feline Endocrine Alopecia

This is a disease of unknown cause. It is presumed to result from hormonal imbalances or deficiencies based on the positive response observed following treatment with specific hormones. The condition is characterized by non-pruritic, symmetric hair loss on the perineum, ventral abdomen, and caudal or medial thighs. Although the alopecia may spread to the flanks, lateral thorax, and proximal tail, the dorsum is usually spared. A thinning of the hair, rather than complete baldness, with normal, non-inflamed skin is the classic presentation. Feline endocrine alopecia primarily affects neutered females and males. However, this syndrome has been reported in intact cats.

Significant controversy exists regarding the relationship of hypothyroidism to feline endocrine alopecia. Affected cats usually have normal baseline serum thyroxine (T4) levels; however, serum T4 levels at 6 hours following stimulation with thyroid-stimulating hormone (TSH) have been low compared with TSH stimulation results in normal cats. These findings suggest that some cats with feline endocrine alopecia may have a low thyroid reserve.

Some cats with hyperthyroidism may develop truncal alopecia, although typically the skin lesions of hyperthyroidism are uncommon and more often associated with a dull, greasy, lusterless haircoat.

Feline hyperadrenocorticism is rare; however, spontaneous and iatrogenic Cushing disease can produce FSA of the trunk or pinnae associated with thin hypotonic skin.

Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Feline Symmetrical Alopecia

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