Panniculitis causes large, tender bumps to form under the skin. They usually occur on the lower legs but can affect other parts of the body.

In this article, learn about the causes and types of panniculitis, as well as how it is treated.

Erythema nodosum is a form of panniculitis. Image credit: James Heilman, MD, (2010, September 18)Share on Pinterest
Erythema nodosum is a form of panniculitis that causes bumps under the skin.
Image credit: James Heilman, MD, (2010, September 18)

Panniculitis is a relatively uncommon skin disorder. It causes large bumps to appear under the skin, usually on the lower legs.

The bumps, also called nodules, are tender to touch and may look red or purple.

Nodules are caused by an inflammation in the layer of fat under the skin. This layer is called the panniculus adiposus and is used for keeping the body warm.

Many types of panniculitis exist, including those caused by infections, cold temperatures, and side effects of medication.

The most common type is erythema nodosum where nodules are found on the shins. This type is most often seen in women and young adults.

The main symptoms of panniculitis include:

  • Large bumps that are tender to touch. The lumps, which may appear red or purple, are located deep underneath the skin and can be several centimeters wide.
  • Bumps on the legs, feet, or arms. Less commonly, bumps may develop on the buttocks, abdomen, and face.
  • Bumps that produce an oily fluid.
  • Bruising in some types of panniculitis.
  • Patches of broken skin called plaques may occur in some types.
  • Signs of general inflammation, including fever, aches and pains, fatigue, and a general feeling of being unwell.

Different types of panniculitis can look similar but have key differences. The exact diagnosis depends on which part of the body is affected and the cause of panniculitis.

A biopsy may be performed during diagnosis, where a sample of a person's skin cells is sent to a lab for evaluation.

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An infection such as tuberculosis or pneumonia may cause panniculitis.

The most common causes of panniculitis are infections, but non-infectious diseases or injuries can also lead to this disorder.

Possible causes of panniculitis include:

  • infections, such as strep throat, tuberculosis, and pneumonia
  • autoimmune disorders, including Crohn's disease, ulcerative colitis, lupus erythematosus, and systemic sclerosis
  • physical causes, such as injury or cold temperatures
  • alpha-1 antitrypsin deficiency, which is an inherited disorder that can cause various lung and liver diseases
  • sarcoidosis is a rare condition involving inflammation of organ and skin tissue
  • some medications, including oral contraceptives and penicillin
  • pregnancy
  • disorders of the pancreas

If the cause is unknown, the condition will be referred to as idiopathic panniculitis.

Although there are many different types of panniculitis, the symptoms are similar in each.

All types are uncommon or rare.

Types of panniculitis include:

  • Erythema nodosum. This is the most common type and refers to bumps and bruises on the shins. A person will also show signs of general inflammation, such as fever and fatigue.
  • Erythema induratum. Bumps are found on the backs of the calves. This type of panniculitis is often related to tuberculosis.
  • Nodular vasculitis. Bumps and inflamed blood vessels occur on the calves and shins.
  • Necrobiosis lipoidica. Bumps and ulcers develop on the lower legs. This type generally affects women with diabetes.
  • Lipodermatosclerosis. A type of panniculitis that is caused by poor vein function in the legs and is linked with obesity. This type is more common in females and older adults.
  • Weber-Christian disease. A relatively severe form of panniculitis that causes general inflammation and organ problems. There is currently no known cause.
  • Pancreatic panniculitis. Caused by pancreas conditions, it is uncommon, affecting just 0.3 to 3 percent of people with pancreas disorders.
  • Lupus erythematosus panniculitis. Caused by lupus, it generally affects the forehead, cheeks, and buttocks but rarely affects the legs.
  • Traumatic panniculitis. This is caused by trauma or injury to the skin.
  • Cold panniculitis. Can occur when skin is exposed to cold temperatures. This type is most common in infants.
  • Gouty panniculitis. In gout, uric acid crystals can build up to cause panniculitis. This often develops in the lower legs and feet.

Medically speaking, the types of panniculitis can be divided into two large groups based on which type of tissue is affected. Inflammations in the fat lobules are called lobular and inflammations in the connective tissue around the fat are called septal.

Most types are both lobular and septal.

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Treatment is not often needed for panniculitis, but in some cases anti-inflammatory drugs may be prescribed.

Panniculitis often resolves without treatment, but certain methods can speed up recovery. The best treatment is to tackle the underlying cause.

If there is no known cause, doctors may treat panniculitis by reducing the inflammation, and in some cases, surgically removing the bumps or affected areas of skin.

Usual treatments for panniculitis include:

  • treating the underlying causes, such as taking antibiotics for infections
  • anti-inflammatory drugs, such as aspirin, naproxen, or ibuprofen
  • compression stockings, which have been shown to help relieve panniculitis symptoms in the legs
  • bed rest to help the body recover
  • corticosteroids
  • surgery to remove the bumps, though this is generally not necessary

The most common form of panniculitis, erythema nodosum, generally resolves without treatment within 2 to 6 weeks. The recovery time depends on the cause of the panniculitis.

Tackling the underlying causes of panniculitis is likely to resolve any related symptoms. After one occurrence, however, there is a chance that this condition can reoccur.

Panniculitis bumps often disappear without any permanent mark, but some types can leave a lasting dent or discoloration on the skin.

A person should talk to a doctor if the bumps do not go away after 6 weeks, if there are lots of bumps, or if symptoms are getting in the way of daily life.