What is genital Crohn disease?
Crohn disease is an inflammatory bowel disease; patients develop granulomas and ulcers in the bowel. Genital Crohn disease describes the skin condition that arises when granulomas affect the genitals and adjacent skin. The skin disease can join up with the bowel disease or be completely separate (in this case it is called metastatic Crohn disease).
Granulomatous genital Crohn disease results in a variety of skin problems, but most often fissures (skin splits).
Who gets genital Crohn disease?
Crohn disease, including genital involvement, can occur at any age; the genital disease is more common in females (a 2:1 ratio).
When genital Crohn disease arises, it is diagnosed at the same time as the intestinal Crohn disease in > 50% of cases. However, it can occur months or even years before the onset of bowel symptoms or at any time afterwards.
Mild genital skin changes such as fissures are relatively common in patients with moderate to severe intestinal Crohn disease. Severe genital disease affects fewer than 8% of people with significant intestinal disease, in the author's experience.
Other skin problems associated with Crohn disease can arise at the same time as granulomatous genital Crohn disease. The most common are:
- Pyoderma gangrenosum
- Orofacial granulomatosis (granulomatous Crohn disease in the mouth or elsewhere on the face)
- Hidradenitis suppurativa
- Erythema nodosum
- Eye inflammation (episcleritis or anterior uveitis)
- Sero-negative arthropathy.
What are the features of genital Crohn disease?
Genital Crohn disease may present with any or all of the following features.
Fissures and erosions
Cracks and erosions arise in the groin creases, around the anus, in between the buttocks, in the folds of the vulva in females and on the foreskin or around the scrotum in males. They are called 'knife-cut' fissures. These fissures and erosions cause soreness or discomfort on urination and may disrupt or prevent normal sexual activity. Full skin thickness ulceration may occur.
Fistulas or tunnels
Fistulas or tunnels may form joining the diseased bowel to the skin. These arise most often when Crohn disease affects the rectum (large bowel). Fistulas may also involve perianal skin, genital skin, the vagina or the vulva.
Genital swelling in Crohn disease is due to Crohn granulomas blocking the lymph vessels. This is known as granulomatous lymphangiopathy or lymphoedema. Females commonly present with swelling of the labia on one or both sides. Males less commonly develop swelling of the penis and scrotum. The lymphoedema tends to get more severe with each flare-up, resulting in distortion of the normal anatomy of the genitals. It can persist long term.
- Skin tags
- Flare-ups of genital and perianal Crohn disease, which may result in painful red papules, plaques or ulcers.
- Secondary bacterial infection or Candida albicans infection
- Pustules and abscesses similar to those seen in hidradenitis suppurativa
How is genital Crohn disease diagnosed?
Genital Crohn disease should be considered as a diagnosis in anyone with a history of inflammatory bowel disease that presents with fissures, ulcers, fistulas and swelling of the genitals.
As skin symptoms can predate bowel disease, genital Crohn disease should also be considered in people with these symptoms that do not have a history of bowel disease; 20–35% of patient with genital Crohn disease do not have gastrointestinal symptoms or disease.
Poor healing is common in Crohn disease. For this reason, biopsies are not always performed. They are useful where there is doubt about the diagnosis or lack of response to treatment.
What is the differential diagnosis of genital Crohn disease?
Other skin conditions affecting the genital area may appear similar to genital Crohn disease. These include:
- Anogenital granulomatosis
- Genital cellulitis and other infections
- Idiopathic genital lymphoedema (with or without obesity)
- Hidradenitis suppurativa
- Pyoderma gangrenosum
- Genital sarcoidosis (another cause of granulomas).
How is genital Crohn disease treated?
Mild Crohn disease is often treated with potent topical corticosteroid ointments or calcineurin inhibitors (tacrolimus ointment or pimecrolimus cream). Tacrolimus should not be applied to ulcerated tissue, as it has been reported to be toxic.
Antiseptic cleansers containing chlorhexidine can reduce secondary infection in any persisting folds or skin fissures. Antibiotics are prescribed for invasive skin infection (cellulitis). Topical antifungal creams and oral antifungal agents are prescribed for a yeast infection (Candida albicans or thrush).
Active genital Crohn disease with lymphoedema requires systemic therapy. This may be incorporated into the treatment regimen for underlying intestinal Crohn disease. Agents used include:
- Oral metronidazole
- TNF-alpha inhibitors such as infliximab or adalimumab (biologic therapies).
Compression underwear, such as is used in sports and cycling, may reduce the lymphoedema. Surgery may be required to remove redundant folds of skin, particularly from the labia minora.
Darvadstrocel, a local administration of expanded adipose-derived stem cells, has been granted marketing authorisation in Europe for the treatment of complex perianal fistula in some circumstances.