Fatty Layer or Nodule Under the Skin in Dogs

The lesions seen in panniculitis can vary in location and number, with most presenting as either soft or firm, sometimes resulting in a painful lump. Panniculitis has been seen both as a localized condition and as a generalized problem over areas of the body. Relatively uncommon, nodules under the skin are most often found on the trunk, footpads, neck, and chest. What may first appear to be a harmless lump could lead to further complications as the lesion begins to grow and weep. In addition, any lump found on your pet should be investigated to rule out the cause or chances of malignancy. There is a breed disposition to fatty nodules under the skin. Panniculitis has been documented most in Dachshunds, with Poodles and Collies also considered at risk. SNP is mainly seen in the German Shepherd breed, although the Chihuahua, Dalmatian, Pomeranian, Brittany Spaniel, and Australian Shepherd are also known to be predisposed.

The inflammation of subcutaneous fat appearing as nodules under the skin is defined in veterinary terms as panniculitis. When there is no known infectious cause, the nodules are classified as sterile nodular panniculitis (SNP). 

The incidence of a fatty layer or nodule appearing on the skin is characterized by the following signs.

• A soft or firm nodule under the skin
• The lesions may move freely
• The skin eventually becomes ulcerated
• There will be a drainage of oily, yellow-brown, reddish or clear fluid
• The nodules may or may not cause pain to the touch
• There can be hair loss in the area
• The lesions are usually found on the trunk
• A lesion that appears to be healing will always leave a scar

Systemic reasons for the panniculitis will often cause fever, lethargy, loss of appetite and depression.

Types

Panniculitis is the occurrence of bumps in the fatty tissue under the skin, brought on by infection such as bacteria.

Sterile Nodular Panniculitis is the formation of single or multiple nodules caused by noninfectious agents like an autoimmune disease.

The tissue around the nodule is being damaged to a degree that will cause extensive scarring and may take a considerable amount of time to heal, even with treatment. Causes are varied; this can only stress the importance of having your pet checked by the veterinarian, to rule out a serious disease or infection that may be brewing concurrently with the skin problem.

Infectious panniculitis

• Bacteria like Actinobacillus
• Fungal infection such as Pythium spp.
• Parasites and protozoa (for example Giardia and coccidiosis)
• Virus

Non infectious panniculitis (SNP)

• Lupus erythematosus
• As a result of injection
• As a result of vaccine (reaction to rabies antigen)
• Liver disease
• Trauma
• Chronic pressure on skin
• Decreased blood supply to area of skin
• Burns
• Pancreatic disease
• Vitamin E deficiency
• Drug reaction

There are studies underway investigating a possible genetic link.

A case of panniculitis can often be diagnosed by the clinical presentation when the veterinarian examines your pet. However, further diagnostics will be done to determine if there is an underlying cause for the fatty layer and nodules. Inform the veterinarian of recent vaccines, health issues or problems that your pet may have encountered in the past. If your canine companion is on medication of any type, give the name of the drug as well as the reason for the prescription.

A dermatological examination will include testing which will involve fine needle aspirate or skin biopsy. Histopathology of the tissue is an accurate way to determine the type of nodule (infectious or noninfectious). Samples of the tissue will be removed by excision and examined under the microscope. This method can rule out diseases like cancer and look for causes like bacteria or fungus. Additionally, standard blood tests (complete blood count and serum biochemistry) will be included in the process as they are good indicators of your pet’s overall health.

Treatment can vary greatly due to the extensive list of causes for fatty layer or nodule under the skin. Of great importance is the treatment of infection such as a fungal invasion because many complications can arise that can make your furry family member sicker. If an infection is left untreated, irreversible damage to the skin can occur and the infection can spread throughout the body. Parasites can cause continued aggressive complications if not eradicated.

If there is an underlying illness responsible for the panniculitis, it must be addressed. For instance, pancreatic or liver complications will need to be corrected in view of the fact that your dog’s health will continue to decline and face consistent damage to vital organs. It should be noted, too that remedying a concurrent disease will often clear up the nodules.

Some treatments that may be administered are glucocorticoid drugs, immunosuppressive therapy (as in systemic lupus erythematosus), antibiotics and antifungals for bacterial, parasitic or fungal invasions, and oral vitamin E alongside dietary management for nutritional deficiencies. In the case of a solitary nodule, excision by surgery may be the protocol choice.

Follow-up visits with the veterinarian will be necessary. The lesions will need to be examined to see if the chosen form of therapy is working. Results may be seen in as little as a week in some cases while others can take several weeks to a couple of months to be resolved. It is important that you prevent your pet from irritating the lesions by excessive licking or biting at the wound or surgical site. Keep in contact with the veterinarian between visits, communicating any concerns you may have about the healing process without delay.