Skin Bumps (Granulomatous Dermatoses) in Dogs

Granulomatous dermatosis is a skin disorder that involves small lesions on the skin with a particular nodular appearance, called granulomas. Granulomas on the skin are generally raised and have a surface that appears grainy to the naked eye. When examined under a microscope a unique cellular pattern can be discerned that identifies the sample as a granuloma. Granulomatous dermatosis can originate in several different ways, and treatment and prognosis for this malady are dependent on the underlying condition.

Granulomatous dermatosis is a skin disorder that involves small raised lesions on the skin with a particular nodular appearance, called granulomas.

Granulomatous dermatoses are most obviously characterized by small inflammatory lesions that have a nodular appearance. These lesions, called granulomas, can appear on any surface of the body. The granulomas themselves have a distinctive cellular pattern that can be distinguished through microscopic inspection. The symptoms related to granulomatous dermatosis condition:

• Bald patches
• Itching
• Raised or ulcerated bumps on the skin (granuloma)
• Redness of the skin
• Scabbing
• Swelling
• Tenderness 
• Thickening of patches of skin
• Weeping from lesions

Diseases which affect other areas of the body as well as the skin may show additional symptoms.

Types

There are several disorders and diseases that can cause granulomas, or that have granulomatous dermatitis as a symptom. This is a sampling of the types of diseases and disorders with granulomas.

Eosinophilic granuloma

• A rare disease in canines associated with unusual reactions to insect bites

Lick granuloma

• This is a granulomatous condition of the skin caused or worsened by a dog compulsively licking a specific spot on their body until a granuloma develops

Juvenile cellulitis (puppy strangles)

• A relatively rare condition occurring in puppyhood that eventually causes skin granulomas, especially on the face and legs

Sarcoidosis

• A multisystemic disease that results in the formulation of granulomas that can affect many bodily organs, including the skin

Because granulomatous dermatoses can arise from a large number of disorders, the causes can be quite diverse.

• Allergy or sensitivity whereby eosinophilic granuloma and flea allergy dermatitis can both ultimately lead to areas of granulomatous dermatosis
• Autoimmune disorders like lupus and pemphigus are autoimmune disorders that can affect the skin and cause granulomatous dermatosis to occur
• Bacterial such as one of the better known bacterial diseases of the skin, leprosy, which often presents with both simple ulcerated nodules and granulomas 
• Behavioral issues such as lick granuloma can be a behavioral issue, although your veterinarian will want to do tests to ensure there isn’t a medical component involved 
• Dermal irritant which can be a skin irritation from chemicals such as bleach or fertilizer and can lead to lesions that become granulomatous in nature
• Fungal invasion like blastomycosis and ringworm which are both fungal diseases that can result in dermal granulomas

In order to make an accurate diagnosis, your veterinarian will start by asking you about your dog, including any medical history or health concerns, current and previous medications, onset of symptoms, and diet and activity levels. A physical examination of the granulomas and the surrounding tissues will also be done, and they will also want to get a sample of the tissue so that it can be examined more closely. A complete blood count, biochemistry profile, skin scraping and urinalysis are also likely to be done at this time as well. 

Under a microscope, the granulomatous lesions will show a unique cellular pattern. Diagnosing the granuloma itself is usually quite simple once the sample is viewed microscopically, but diagnosing what caused the granuloma can prove to be more elusive. Tests to diagnose the original cause could include biopsy of skin samples, fungal cultures, bacterial cultures, intradermal allergy tests, and x-rays.

Treatment methods for granulomatous dermatoses are as varied as the causes of the disorder itself. Bacterial origins will most often be treated with antibiotics in pill form or as a topical solution, and your veterinarian is likely to offer antifungal treatment options of ointments, oral medication, and shampoos for fungal infestations. The medications for fungal disorders are often prescribed for longer periods of time than the antibiotic medication as they can be particularly stubborn to eradicate. Specialized topical treatments such as antihistamines or steroids may be used as well for reactions to irritants to your dog’s skin.

Autoimmune disorders, which may manifest with granulomas on both the skin and other surfaces, are treated corticosteroids to reduce any inflammation and with chemotherapy, using cytotoxic drugs to suppress the immune system. Dogs tolerate chemotherapy better than most humans and only around 5% require hospitalization from the treatment itself. Some breeds (English Sheepdog, Lhasa Apso, Maltese, Schnauzer, Shih Tzu, and Poodle) are more prone to hair loss. If the underlying condition caused internal granulomas that are interfering with optimal health, surgery may be required to remove the tissue as well.

The prognosis for your pet is dependent on the underlying cause. It is essential to follow your veterinarian’s instructions regarding any medications and continue them for the full amount of time that is recommended, even if symptoms appear to be under control. If your companion is treated using cytotoxic medication (chemotherapy) your veterinarian will probably want to do regular checks on your dog’s liver and kidney enzyme levels. Pets are often sent home the same day after chemotherapy, and although most of the drug is metabolized within just a few hours, some remnants of it can remain in the blood for a few days. It is important to use gloves when dealing with bodily fluids, and maintain good hand washing hygiene. Children, pregnant and nursing women and immunocompromised adults should avoid contact with the bodily fluids during that time.