Panniculitis

What is panniculitis?

Panniculitis refers to a group of conditions characterised by inflammation of the fat layer below the skin (sub-cutaneous fat). It can be localised to a particular part of the body or involve larger areas.

Panniculitis may present as thickening or hardening of the skin. Frequently there are tender or painful nodules, most often on the legs. There is usually also reddening or darkening of the skin.

What causes panniculitis?

A wide range of conditions may cause panniculitis including potentially life-threatening conditions such as lupus, pancreatic disease and alpha-1 anti-trypsin deficiency. Panniculitis may also be a reactive process and may occur at a result of infections or intake of certain drugs. There may be an associated vasculitis (inflammation of blood vessels) as well.

Two of the most common causes of panniculitis, erythema nodosum and lipodermatosclerosis are discussed below.

Erythema nodosum

The most common acute panniculitis is erythema nodosum (EN) which appears as tender, hard lumps typically over the front of the shins.

EN is more common in women and typically does not form ulcers. EN is not a disease but a reaction pattern to an underlying condition, a drug or an infection.

The eruption generally lasts 3 to 6 weeks but in some cases becomes chronic. It recurs frequently.

EN is best treated with supportive care using aspirin, bed rest and compression.  Because damaged fat is very slow to heal, it can take weeks to assess the response to treatment and often months before the lesions totally resolve.

Lipodermatosclerosis

Lipodermatosclerosis (LDS) means hardening (sclerosis) of fat (lipo-) and skin (-dermato). This condition is seen in late stages of venous disease (varicose veins or deep vein thrombosis). The area just below the calf muscle goes very hard and pigmented and takes on a woody texture. In extreme cases the leg appears as an inverted champagne bottle.

People with varicose veins should be aware of the long-term risks of not treating varicose veins and seek help before LDS occurs. Once LDS occurs, treating the underlying veins may prevent LDS from progressing into ulceration but does not necessarily make the skin feel normal again. In other words, when LDS happens, it is permanent in most cases.

How is panniculitis diagnosed?

Multiple biopsies of skin and fat are often required to identify the underlying condition. Diagnosis is frequently difficult as it requires adequate tissue to be obtained for analysis. A variety of blood tests and other investigations may be required.

The presence of panniculitis may represent an underlying disease and other specialists may need to be involved in planning management and treatments. Investigations may be required to exclude, more serious, underlying conditions such as sarcoidosis, scleroderma, lupus or leprosy.

How is panniculitis treated?

Treatment is directed towards the underlying cause of the condition. Symptoms may be treated with rest and elevation, compression hosiery and analgesics and/or anti-inflammatories.

Panniculitis may wax and wane and may take months to years to resolve despite active treatment.

This information has been written by Clinical Associate Professor Kurt Gebauer
Updated 03 March 2016