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Sterile Nodular/Granulomatous Dermatoses in Cats

Sterile nodular/granulomatous dermatoses are diseases in which the primary lesions or masses of tissue, are solid, elevated, and greater than one centimeter in diameter. These nodules are usually the result of an infiltration of inflammatory cells into the skin and be a reaction to interal or external stimuli.

Symptoms and Types

• Nodular dermatofibrosis
• Calcinosis circumscripta
• Malignant histiocytosis

Causes

• Amyloidosis (a waxy protein deposit, or amyloid, in the body)
• Reaction to foreign body
• Spherulocytosis (disease of red blood cells)
• Idiopathic sterile granuloma and pyogranuloma
• Calcinosis circumscripta (skin stones, similar to calcinosis cutis)
• Malignant histiocytosis (abnormally spreading immune-type cells)
• Cutaneous histiocytosis (immune-type cells spreading to skin)
• Sterile panniculitis (inflammation of the skin)
• Nodular dermatofibrosis (bumps filled with excess elastic skin material which accompanies kidney disease)
• Cutaneous xanthoma (a benign skin problem, involving immune cell infiltration usually accompanies hyperlipoproteinemia or diabetes mellitus)

Diagnosis

Your veterinarian will perform a thorough physical exam on your cat, with a blood chemical profile, a complete blood count, an electrolyte panel and a urinalysis. You will need to provide a thorough history of your cat's health leading up to the onset of symptoms.

The physical exam should include a dermatologic exam, during which skin biopsies for histopathology can be taken to determine if structural changes have occurred in the tissue. Skin scrapings will also be examined microscopically and cultured for bacteria, mycobacteria and fungi.

Treatment

Most of these skin disorders can be treated on an outpatient basis, unless they have reached a severe stage. A few of these disorders, such as malignant histiocytosis, amyloidosis, and nodular dermatofibrosis, are almost always fatal. Cats with calcinosis cutis may need to be hospitalized for sepsis and intense topical therapy.

Some of the other forms of dermatoses with nodules or granulomas are discussed below:

• Amyloidosis: no known therapy, unless the lesion is solitary and can be surgically removed
• Spherulocytosis: the only effective treatment is surgical removal
• Foreign body reactions are best treated by removal of the offending substance if possible
• For hair foreign bodies, the cat should be placed on softer bedding and topical therapy with keratolytic agents should be initiated. Many cats with hair foreign bodies also have secondary deep bacterial infections that need to be treated with both topical and systemic antibiotics
• Malignant histiocytosis: no effective therapy. It is rapidly fatal
• Calcinosis cutis: underlying disease must be controlled if possible. Most cases require antibiotics to control secondary bacterial infections. Hydrotherapy and frequent bathing in antibacterial shampoos minimize secondary problems. If lesions are extensive, serum calcium levels should be monitored closely
• Calcinosis circumscripta: surgical excision is the therapy of choice in most cases
• Sterile panniculitis: single lesions can be removed surgically
• Nodular dermatofibrosis: no therapy for most cases, because the cystadenocarcinomas are usually bilateral
• For the rare unilateral case of cystadenocarcinoma or a cystadenoma, removal of the single affected kidney may be helpful
• Cutaneous xanthoma: correction of the underlying diabetes mellitus or hyperlipoproteinemia is usually curative

Living and Management

Your veterinarian will prescribe medication dependent upon your cat's diagnosis and condition. Bloodwork and a urinalysis will need to be performed every six months if your cat is taking long-term glucocorticoids. If your cat is taking dimethylsulfoxide for calcinosis cutis, bloodwork should be performed every 1-2 weeks to monitor calcium levels until they are regulated.