Crohn skin disease

Crohn disease is an inflammatory bowel disease that involves inflammation of the small intestine. This can cause pain, fever, constipation, diarrhoea and weight loss. Extraintestinal features are common in Crohn disease and include arthritis, skin problems, inflammation in the eyes or mouth, gallstones and kidney stones. It affects about 1 in 300 Europeans and has peak onset in the teens and 20s.

Skin lesions are often seen in patients with Crohn disease. When granulomatous lesions of Crohn disease involve sites other than the gastrointestinal tract then the disease is then termed metastatic Crohn disease.

What are the signs and symptoms?

Skin involvement occurs in about 40% of patients with Crohn disease. Often the involvement is an extension of the intestinal disease and presents as skin tags, swelling, fissures and abscesses around the perineal and perianal region. Painful vulval or scrotal ulceration may occur. However, any part of the skin can be affected.

Lesions may present as spots or plaques found on the trunk, arms and legs, and they may be mildly itchy. In some cases distinctive dermatoses are present. These include:

• Pyoderma gangrenosum
• Neutrophilic dermatosis / Sweet syndrome, typically with pustules
• Pyodermatitis-pyostomatitis vegetans, a purulent erosive dermatosis characterised by snail-track ulcers
• Erythema multiforme
• Erythema nodosum
• Acneiform eruptions including nodulocystic acne, hidradenitis suppurativa and folliculitis
• Palisaded neutrophilic and granulomatous dermatitis
• Necrotizing and granulomatous small vessel vasculitis.

Occasionally, skin lesions may occur before any signs or symptoms of the intestinal disease.

Oral involvement occurs in 8-9% of Crohn disease and includes:

• Gingival or mucosal swelling
• Cobblestoning of the buccal mucosa
• Aphthous ulcers
• Mucosal tags
• Angular cheilitis
• Granulomatous cheilitis

Skin complications of Crohn disease

*	*	*
Episcleritis *	Granulomatous cheilitis	Oral disease Image supplied by Tami Yap
* Images from: Sheikh A, Aldameh A, Symmans P, Hill A. New Zealand Medical Journal. 2006;119(1247). URL: http://www.nzma.org.nz/journal/119-1247/2363/ (with permission)

Secondary skin eruptions

Crohn disease affecting the gut may lead to malnutrition. Iron deficiency and vitamin deficiencies may present as skin or oral ulceration, persistent infections or pellagra.

Drugs prescribed for Crohn disease may also lead to adverse effects on the skin.

Diagnosis of Crohn skin disease

Skin biopsy of the lesion is performed. Under microscopy, the presence of non-caseating granulomas similar to those found in intestinal Crohn disease supports the diagnosis of Crohn skin disease. In patients with no intestinal disease whose skin biopsy come up with non-caseating granulomas, a thorough gastrointestinal history and systemic work-up should be performed.

The presence of anti-Saccharomyces cerevesiae (ASCA) antibodies in the blood are very suggestive of Crohn disease, with 60% sensitivity and 90% specificity.

* Granuloma on skin pathology

What is the treatment of Crohn skin disease?

Treatment for Crohn skin disease is palliative not curative. Treatment of the intestinal manifestations usually improves the skin lesions. These may include oral corticosteroids, intralesional steroids, antibiotics such as metronidazole, methotrexate, azathioprine, sulfasalazine and new anti tumour necrosis factor agents such as infliximab and adalimumab.