During a medical mission trip to Africa a child was seen with pyoderma gangrenosum on the dermatology ward of a hospital. She has had a long history of pyoderma gangrenosum with ulcerations on her face, neck, and chest (Figure 149-1). The scarring has caused adhesions between the face, neck, and chest.

Pyoderma gangrenosum (PG) is an uncommon ulcerative disease of the skin of unknown origin that affects both children and adults. It is a type of neutrophilic dermatosis.

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  PG occurs in approximately 1 person per 100,000 people of all ages each year.¹

  
  
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  Children account for only 3 to 4 percent of the total number of cases. There is nothing clinically distinctive about pyoderma gangrenosum in children and adolescents other than the age of the patients.²

  
  
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  No racial predilection is apparent.

  
  
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  A slight female predominance may exist.

  
  
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  Predominately occurs in fourth and fifth decade, but all ages may be affected.

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  Etiology is poorly understood.

  
  
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  Pathergy (initiation at the site of trauma or injury) is a common process and it is estimated that 30 percent of patients with PG experienced pathergy.¹

  
  
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  Up to 50 percent of all cases are idiopathic.³

  
  
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  At least 50 percent of cases are associated with systemic diseases such as inflammatory bowel disease, hematologic malignancy, and arthritis.³

  
  
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  It occurs in up to 5 percent of patients with ulcerative colitis and 2 percent of those with Crohn disease (Figure 149-2).^4,5

  
  
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  In one study of 46 patients 18 years of age or younger with pyoderma gangrenosum, an underlying systemic disease was present in 74 percent of the older children, and as in adults it was most commonly ulcerative colitis.²

  
  
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  The lesions tend to affect the lower extremities (Figure 149-3), but infants tend to have ulcers more commonly than adults in the genital and perianal distribution, ⁶ the head and face (Figure 149-1), and the buttocks (Figure 149-4).⁷

  
  
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  Biopsies usually show a polymorphonuclear cell infiltrate with features of ulceration, infarction, and abscess formation.

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  Ulcerative colitis.

  
  
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  Crohn disease.^3,8

  
  
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  Polyarthritis (seronegative or seropositive).

  
  
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  Hematologic diseases/disorders such as leukemia (predominantly myelocytic).

  
  
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  Monoclonal gammopathies (primarily immunoglobulin A).

  
  
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  Psoriatic arthritis and rheumatoid arthritis.

  
  
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  Hepatic diseases (hepatitis and primary biliary cirrhosis).

  
  
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  Immunologic diseases (lupus erythematosus and Sjögren syndrome).

Clinical Features

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  Typically PG presents with deep painful ulcer with a well-defined border, which is usually violet or blue (Figures 149-3 and 149-4). The color has also been described as the color of gun metal. The ulcer edge is often undermined and the surrounding skin is erythematous and indurated. It usually starts as a pustule with an inflammatory base, an erythematous nodule, or a hemorrhagic bulla on a violaceous base. The central area then undergoes necrosis to form a single ulcer.⁸

  
  
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  The lesions are painful and the pain can be severe.³ Patients may have malaise, arthralgia, and myalgia.

  
  
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  Two main variants of PG exist: classic and atypical.³

  
  
  
  
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    Classic PG is characterized by a deep ulceration with a violaceous border that overhangs the ulcer bed.³ These lesions of PG most commonly occur on the legs (Figure 149-3).³

    
    
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    Atypical PG has a vesiculopustular wet component. This is usually only at the border, is erosive or superficially ulcerated, and most often occurs on the dorsal surface of the hands, the extensor parts of the forearms, or the face.³

  
  
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  Other variants:

  
  
  
  
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    Peristomal PG may occur around stoma sites. This form is often mistaken for a wound infection or irritation from the appliance.⁹

    
    
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    Vulvar or penile PG occurs on the genitalia and must be differentiated from ulcerative sexually transmitted diseases (STDs) in adolescents such as chancroid and syphilis.³

    
    
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    Intraoral PG is known as pyostomatitis vegetans. It occurs primarily in patients with inflammatory bowel disease.³