Pyoderma gangrenosum is a chronic, neutrophilic, progressive skin necrosis of unknown etiology often associated with systemic illness and sometimes skin injury.
Etiology is unknown, but pyoderma gangrenosum can be associated with various systemic illnesses, including vasculitis, gammopathies, RA, leukemia, lymphoma, hepatitis C virus infection, SLE, sarcoidosis, polyarthritis, Behçet disease, hidradenitis suppurativa, and especially inflammatory bowel disease. It is thought to be mediated by an abnormal immune response. Most patients are age 25 to 55. It can manifest in various subtypes.
Pathophysiology of pyoderma gangrenosum is poorly understood but may involve problems with neutrophil chemotaxis. IL-8 is overexpressed in lesions. Ulcerations of pyoderma gangrenosum occur after trauma or injury to the skin in about 30% of patients; this process is termed pathergy.
Most often, pyoderma gangrenosum begins as an inflamed erythematous papule, pustule, or nodule. The lesion, which may resemble a furuncle or an arthropod bite at this stage, then ulcerates and expands rapidly, developing a swollen necrotic base and a raised dusky to violaceous border. An undermined border (ie, loss of underlying support tissue at the border) is common, if not pathognomonic. Systemic symptoms such as fever and malaise are common. The ulcers can coalesce to form larger ulcers, often with cribriform or sieve-like scarring.
Symptoms and signs can vary with the subtype:
Ulcerative (classic) subtype: In this most common subtype, ulcers form as described above, most commonly on the lower extremities or trunk, particularly the buttocks and perineum.
Bullous (atypical) subtype: This less common subtype often develops in patients with hematologic disorders. Lesions usually begin as bullae that erode, becoming superficial ulcers. The arms and face are most often involved.
Pustular subtype: This subtype tends to develop during exacerbations of inflammatory bowel disease. Painful pustules develop, surrounded by erythema. Arthralgias are common.
Vegetative (superficial granulomatous pyoderma) subtype: In this subtype, a single, indolent, mildly painful plaque or superficial ulcer develops, most often on the head or neck. The border is not undermined and the base is not necrotic.
Pyoderma gangrenosum can also develop at other sites, such as around a stoma in patients who have inflammatory bowel disease (peristomal pyoderma gangrenosum), on the genitals (genital pyoderma gangrenosum), or in sites other than the skin, such as the bones, cornea, CNS, heart, intestine, liver, lungs, or muscle (extracutaneous pyoderma gangrenosum).
Diagnosis is clinical and is a diagnosis of exclusion after other causes of ulceration have been ruled out. Expansion of ulceration after surgical debridement strongly suggests pyoderma gangrenosum. Biopsies of lesions are not often diagnostic but may be supportive; 40% of biopsies from a leading edge show vasculitis with neutrophils and fibrin in superficial vessels.
Patients who have bullous (atypical) pyoderma gangrenosum should be monitored with periodic clinical assessment and CBC for development of a hematologic disorder.
Wound healing can be promoted with moisture-retaining occlusive dressings for less exudative plaques and absorptive dressings for highly exudative plaques. Wet-to-dry dressings should be avoided. Topical therapy with high-potency corticosteroids or tacrolimus can help with superficial and early lesions.
For more severe manifestations, prednisone 60 to 80 mg po once/day is a common first-line therapy. TNF-alpha inhibitors (eg, infliximab, adalimumab, etanercept) are effective, particularly in patients who have inflammatory bowel disease. Cyclosporine 3 mg/kg po once/day is also quite effective, particularly in rapidly progressive disease. Dapsone, azathioprine, cyclophosphamide, methotrexate, clofazimine, thalidomide, and mycophenolate mofetil have also been used successfully. Antimicrobials such as minocycline have also been used for vegetative (superficial) pyoderma gangrenosum.
Surgical treatments are avoided because of the risk of wound extension.
Pyoderma gangrenosum is often associated with a systemic disorder and is probably immune-mediated.
There are several subtypes; the ulcerative subtype (ie, necrotic base and raised violaceous border with undermined edge on a lower extremity, buttock, or perineum) is most common.
Diagnose pyoderma gangrenosum clinically.
Optimize wound care and avoid surgical debridement.
Use topical potent corticosteroids or tacrolimus to treat early lesions and use systemic corticosteroids, TNF-alpha inhibitors, or other anti-inflammatories or immunosuppressants to treat more severe manifestations.