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Panniculitis

Author: Dr Amy Stanway, Dermatology Registrar, Waikato Hospital, Hamilton, New Zealand, 2002. Updated by A/Prof Amanda Oakley, February 2016.


What is panniculitis?

Panniculitis refers to a group of conditions that involve inflammation of subcutaneous fat. Despite having very diverse causes, most forms of panniculitis have the same clinical appearance. The diagnosis is established by a skin biopsy, as there are characteristic microscopic features depending on the cause. The most common form of panniculitis is erythema nodosum.

Panniculitis is classified as mostly septal panniculitis or mostly lobular panniculitis depending on the site of the most intense microscopic inflammation. Most types of panniculitis have both septal inflammation (early) and lobular inflammation (later). Further classification is based on whether or not there is subcutaneous vasculitis, and the type of inflammation noted (neutrophils, lymphocytes, histiocytes, granulomas).

Classification of panniculitis

Mostly septal panniculitis with vasculitis

Mostly septal panniculitis without vasculitis

Mostly lobular panniculitis with vasculitis

Mostly lobular panniculitis without vasculitis

Neutrophilic panniculitis

What are the clinical features of panniculitis?

Panniculitis presents typically with:

  • Thickened and firm nodules and plaques
  • Erythematous or pigmented overlying skin
  • Pain and tenderness.

Sometimes, lesions resolve to leave localised subcutaneous atrophy (lipodystrophy).

Associated symptoms of fever, malaise and arthralgia are common.

Panniculitis

How is panniculitis diagnosed?

Panniculitis is diagnosed and classified by a combination of clinical features, biopsy findings and microbiological culture. Sometimes other investigations are necessary (such as chest X-ray in erythema nodosum and alpha-1 antitrypsin levels).

The histopathology may show the inflammation to be lobular, septal or mixed, with or without vascular damage, and predominantly neutrophils, lymphocytes or granulomatous.

What is the treatment of panniculitis?

Treatment of panniculitis includes:

What is the outcome of panniculitis?

The outcome depends on the underlying cause of the inflammation. After an inflammatory phase of weeks to months, panniculitis often settles down. It may recur. Some forms of panniculitis do not leave a mark, but destructive forms of panniculitis tend to leave a permanent dent in the skin.

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References

  • Wick MR. Panniculitis: A summary. Semin Diagn Pathol. 2016 Dec 27. pii: S0740-2570(16)30110-1. doi: 10.1053/j.semdp.2016.12.004. [Epub ahead of print] PubMed PMID: 28129926. PubMed.

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