Chapter 37: Pyoderma Gangrenosum

AT-A-GLANCE

• Pyoderma gangrenosum (PG) is an uncommon, neutrophilic inflammatory skin condition, which classically presents as a painful nodule, plaque, or pustule that enlarges and breaks down to form a progressively enlarging ulcer with raised, undermined, violaceous borders and a surrounding zone of erythema. Healing PG lesions develop a cribriform appearance.

• PG tends to occur and recur in areas of trauma because of the pathergic phenomenon, where trauma or irritation can induce flaring of PG.

• PG most often occurs in association with systemic inflammation, and most reported cases have an associated underlying disease (such as inflammatory bowel disease, monoclonal gammopathy, hematologic disease, inflammatory arthritis, malignancy, hidradenitis suppurativa, etc); however, PG may precede these disorders. PG has also been reported in association with genetic mutations and syndromes, such as the pyogenic arthritis, pyoderma gangrenosum, and acne (PAPA) syndrome, or without an identifiable underlying disease.

• PG most commonly presents as the classic ulcerative variant, but may also arise as bullous, pustular, or vegetative variants. Clinical features of different variants sometimes overlap in individual patients but usually one variant dominates the clinical picture.

• There is no laboratory test or investigation that establishes the diagnosis of PG with certainty. The histopathologic findings are not diagnostic but can be supportive of the diagnosis of PG in the appropriate clinical setting and are essential to rule out alternative diagnoses.

• Specified criteria (see “Diagnostic Algorithm” section) suggest the diagnosis of PG, but other conditions (particularly infection, vascular disease, and malignancy) must be excluded.

• The mainstays of management are systemic immunosuppressive agents together with appropriate local and topical therapy.

• Classic ulcerative PG is a chronic condition. Complete healing usually requires months of treatment; maintenance therapy is necessary in many and relapses are common. Significant morbidity and mortality are experienced by patients with ulcerative and bullous PG.