Alopecia

Abstract

PHOTOS 1-3: Alopecia is abnormal hair loss or failure of hair to grow and occurs in a variety of conditions. Alopecia areata causes patchy alopecia. Alopecia areata is the result of cellular and humoral immune response against hair follicle antigens. It is a spontaneously occurring, non pruritic focal to multifocal condition. The patchy areas of alopecia may give the coat a moth eaten appearance. Hyperpigmentation (melanoderma) may develop in the alopecic skin. In dogs with multicoloured coats the alopecia may first occur in the pigmented areas. The lesions occur most commonly on the head, neck and legs. Facial lesions are usually bilaterally symmetrical. Alopecia areata is diagnosed via dermatohistopathology. There is no specific treatment for alopecia areata and spontaneous hair regrowth may be seen. Hair that regrows may be permanently white. PHOTOS 4-10: Alopecia X is an uncommon condition in dogs that may be due to local follicular receptor dysregulation, hyperadrenocorticism, growth hormone deficiency, adrenal sex hormone imbalance or excessive production of androgenic steroids. It usually occurs in dogs between 2 and 5 years of age and occurs in Chow Chows, Pomeranians, Keeshonds, Samoyeds, Alaskan Malamutes, Siberian huskies and miniature poodles. Hair loss is seen from the neck, tail, caudodorsum, perineum and caudal thighs. The alopecia becomes generalized over the trunk but the head and front limbs are spared. Hair loss is bilaterally symmetrical and the remaining hairs epilate easily. The alopecic skin may become hyperpigmented, thin and hypotonic with or without secondary seborrhoea and superficial pyoderma. Diagnosis is via dermatohistopathology and ACTH stimulation test. A variety of medical therapies are available to stimulate hair regrowth. Neutering intact dogs may induce hair regrowth. Canine hypothyroidism is a more common condition in dogs which also causes alopecia. Alopecia on the bridge of the nose is an early symptom of this condition. The hair coat may be dull, dry and brittle with bilaterally symmetrical alopecia that spares the extremities. The alopecic skin may be hyperpigmented and thickened. Secondary yeast infections of seborrheic skin are common.

REFERENCES: PHOTOS 1-10: Medleau, L & Hnilica, KA 2006, ‘Small animal dermatology: a color atlas and therapeutic guide’, 2nd ed., Saunders Elsevier, St. Louis, pp.241-249, 269.