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  icon Rare
  icon Not so common
  icon Common
  icon Low morbidity
  icon Considerable morbidity
  icon Serious

Pyoderma Gangrenosum (PG)

ICD-9: 686.01 ○ ICD-10: L88 Image not available.

  • PG is an idiopathic, either acute or chronic, severely debilitating skin disease.

  • It is characterized by neutrophilic infiltration, destruction of tissue, and ulceration.

  • It occurs most commonly in association with a systemic disease, especially arthritis, inflammatory bowel disease, hematologic dyscrasias, and malignancy, but may also occur alone.

  • Characterized by the presence of painful, irregular, boggy, blue-red ulcers with undermined borders and purulent necrotic bases.

  • There is no laboratory test that establishes the diagnosis.

  • The mainstays of treatment are immunosuppressive or modulating agents.

  • Relapses occur in most patients and there is significant morbidity.


Rare, prevalence unknown. All age groups affected with a peak between 40 and 60 years. Slight preponderance of females.

Etiology and Pathogenesis

Unknown. Although called pyoderma, it does not have a microbial etiology. PG is counted among the neutrophilic dermatoses because of the massive neutrophilic infiltrates within the skin.

Clinical Manifestation

Three Types

Acute. Acute onset with painful hemorrhagic pustule or painful nodule either de novo or after trauma. There is the phenomenon of pathergy, where a needle stick, insect bite, biopsy, or other minimal trauma can trigger a lesion. Chronic: slow progression with granulation and hyperkeratosis. Less painful. Bullous: true blisters often hemorrhagic and associated with hematologic disease.

Skin Lesions

Acute. Superficial hemorrhagic pustule surrounded by erythematous halo; very painful (Fig. 7-1). Breakdown occurs with ulcer formation, whereby ulcer borders are dusky-red or purple, irregular and raised, undermined, boggy with perforations that drain pus (Fig. 7-2). The base of the ulcer is purulent with hemorrhagic exudate, partially covered by necrotic eschar (Fig. 7-3), with or without granulation tissue. Pustules both at the advancing border and in the ulcer base; a halo of erythema spreads centrifugally at the advancing edge of the ulcer (Fig. 7-3). Chronic: lesions may slowly progress, grazing over large areas of the body and exhibiting massive granulation within the ulcer from the outset (Fig. 7-4) and crusting and even hyperkeratosis on the margins (Fig. 7-5). Lesions are usually solitary but may be multiple and form clusters that coalesce. Most common sites: lower extremities (Figs. 7-2 and 7-5) > buttocks > abdomen (Fig. 7-3) > face (Fig. 7-4). Healing of ulcers results in thin atrophic cribriform scars. Bullous: blisters from the outset, often hemorrhagic, followed by ulceration.

Figure 7-1.

Pyoderma gangrenosum The initial lesion is a rapidly enlarging hemorrhagic nonfollicular pustule surrounded by an erythematous halo and is very painful.

Figure 7-2.

Pyoderma gangrenosum Lesions rapidly break down in the center and become boggy, hemorrhagic, and purulent ulcers. Note small abscesses at ...

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