Acanthosis Nigricans

This is a rare disease of melanosis type with seen exclusively in Dachshunds. It begins with subtle symmetrical hyperpigmentation in the armpits. The early lesions then progress slowly to hair loss. Greasy, smelly debris accumulate in more severely affected dogs. The abdomen, groin, chest, anal area, forelimbs and hock may all be involved.

The term "acanthosis nigricans" also has been used generically to describe clinical skin reaction pattern which is characterized by visually similar lesions and is seen in a variety of breeds. Acanthosis nigricans is similar to chronic hyperplastic dermatitis, particularly due to allergy, but may be less inflamed.

Diagnosis

A careful history and physical examination is performed to identify an underlying cause. Skin scrapings are performed to rule out demodicosis, especially in young dogs. Impression smears are useful to identify bacterial and Malassezia infections.

Affected animals should not be bred in order to avoid possible propagation of the defect, in the event that there is an inheritable basis.

Treatment of Acanthosis Nigricans

Primary acanthosis nigricans in Dachshunds is not curable. Early cases may respond to shampoo therapy and local topical glucocorticoids, for example, betamethasone valerate ointment. As lesions progress, more aggressive systemic therapy may be useful. In secondary acanthosis nigricans, the lesions will spontaneously resolve after identification and correction of the underlying cause. However, this will not occur if secondary bacterial and yeast pyodermas are not treated appropriately.

Vitamin E has been successfully used in the treatment of a variety of skin diseases including discoid and systemic lupus erythematosus, dermatomyositis, and epidermolysis bullosa simplex. Vitamin E is rarely successful alone in the management of these conditions, but offers a relatively nontoxic aid to therapy.

Chronic Hyperplastic Dermatitis

Chronic hyperplastic dermatitis, sometimes referred to as "dermatitis reaction", is seen primarily in the dog. The main signs of this condition is intense itch and self-trauma. Crusting is another common feature. Chronic allergy is the most common cause. It may look like other chronic skin diseases such as pyoderma or cornification disorders.

Use of Betamethasone

Betamethasone is an anti-inflammatory (corticosteroid) drug which depresses the formation, release, and activity of elements involved in inflammation, such as prostaglandins, kinins, and histamine. This drug may cause immune suppression. Prolonged use of steroids may promote the development of cataracts and glaucomas.

References:

1. Lowell Ackerman. Owner's Guide to Dog Health.
2. Peter J. Ihrke, Emily J. Walder, Verena K. Affolter, and Thelma Lee Gross. Skin Diseases of the Dog and Cat.
3. The Merck Veterinary Manual. Acanthosis Nigricans: Introduction.