Pyoderma Gangrenosum

Pyoderma gangrenosum is an uncommon, ulcerating condition of the skin. It was first described in 1930. The aetiology is unknown. At least half of the cases are associated with other diseases, especially inflammatory bowel disease. In about 30% of patients it follows trauma and this is called pathergy.

There are two variants of this disease. The classic form usually appears on the legs but an atypical and more superficial variation can occur on the hands. Other tissues may be involved with sterile, neutrophilic abscesses. Hence it would seem to be an inflammatory condition but not the result of infection. The other sites to be involved include the heart, the central nervous system, the alimentary canal, the eyes, the liver, the spleen, bones, and lymph nodes.

The age of onset of both classic and atypical disease is similar but the classical is more likely to be associated with other disease. It more often affects the lower limb whilst atypical tend to affect the upper limb. The classic tends to heal slightly faster. The mean healing times for classic and atypical are 11.5 and 9 months respectively but the range is wide.¹

The incidence is about 1 person in 100,000 per year. The peak incidence is in the 4th and 5th decades with 3 or 4% occurring in children. In childhood there is often underlying disease.² There is a slight female preponderance.

History

• The lesion starts as a small, red papule or pustule before becoming larger and ulcerating.
• A prominent complaint is pain in the lesion.
• There may be arthralgia and malaise.
• Ask about systemic disease, especially inflammatory bowel disease. It may be pre-existing or it may present at the same time as the lesions.

Examination

• The classic form has deep ulceration with a violaceous border that overhangs the ulcer bed.
• They are usually on the legs but can occur elsewhere.
• The atypical variation is vesiculopustular. It is eroded or superficially ulcerated. It usually occurs on the dorsal surface of the hands, the extensor parts of the forearms, or the face.
• It can occur around stoma sites, usually related to inflammatory bowel disease. This may easily be mistaken for a wound infection or irritation from the stoma bag.
• It may sometimes occur on the genitalia and a sexually transmitted disease may be suggested by such an appearance.
• An intraoral form, named pyostomatitis vegetans, is usually limited to patients with inflammatory bowel disease.³

• Venous ulceration
• Acute febrile neutrophilic dermatosis (Sweet syndrome)
• Behcet's Disease
• Syphilitic chancre
• Tuberculosis
• Churg-Strauss Syndrome or polyarteritis nodosa
• Ecthyma
• Herpes simplex
• Squamous cell carcinoma
• Mycosis fungoides
• Antiphospholipid syndrome
• Dermatitis artefacta

• FBC, ESR check for general inflammatory disease
• U&E, creatinine
• LFTs
• Urinalysis: Protein may be present in myeloma or systemic lupus erythematosis
• VDRL and autoantibody screen, including antiphospholipid antibodies
• Wound swabs and skin biopsy with culture are usually required but biopsy sites may heal poorly
• Doppler studies may be necessary to check vascular integrity
• Bone marrow examination may be indicated
• Bowel investigations are unlikely to be rewarding unless the history points to it

• Ulcerative colitis
• Crohn's disease
• Seronegative arthritis or seropositive arthritis. This may include psoriatic arthropathy.
• Hepatitis and primary biliary cirrhosis
• Monoclonal gammopathies, usually IgA and IgA myeloma
• Systemic lupus erythematosis and Sjögren's disease

The evidence base of management is poor as this is a rare condition and so it is difficult to conduct RCTs.

Where there is an underlying disease it should be treated and this may improve the skin lesions too. Topical therapy is generally aimed at suppressing the inflammatory process:

• General wound care and dressings.
• Very potent topical steroids creams may be effective for small lesions.
• Systemic corticosteroids are the usual treatment and usually at very high doses, perhaps starting at up to 120mg per day. Pulsed steroids are traditionally the first line of treatment but ciclosporin may be better.⁴ It can be used with or without steroids.
• Other treatments include ciclosporin, azathioprine, dapsone, tacrolimus, cyclophosphamide, thalidomide and tumour necrosis factor-alpha (TNF-α) inhibitors have all been tried. Chlorambucil is steroid sparing.⁵
• Other topical treatments include 2% sodium cromoglicate solution, nitrogen mustard, and 5-aminosalicylic acid.
• Topical tacrolimus⁶ and pimecrolimus that are immune modifiers may be useful. Infliximab has been used.⁷
• Hyperbaric oxygen may be valuable, especially in difficult cases.⁸
• In children the face and genital areas are more often affected than in adults but treatment is similar and steroids are usually effective.⁹

Surgery is best avoided as healing is poor. Sometimes total colectomy for ulcerative colitis will put the disease into remission. It may occur in a stoma.

Incorrect diagnosis may lead to skin grafting and even the harvest site is liable to break down.

Failure of early diagnosis and effective treatment may lead to amputation of the affected limb or life-threatening infection and septicaemia.

• Most cases do well but recurrences may occur
• Residual scarring of lesion is usual
• Many patients improve with immunosuppressive therapy
• Some patients have a refractory course and multiple therapies fail. They are very difficult to manage.
• Patients with arthritis tend to be more refractory to treatment¹⁰
• If there is pathergy, protection of the skin from trauma may prevent a recurrence