Higher white blood cell counts indicate infection. Mild anemia may be present. Electrolytes values may be abnormal with severe skin and mucous membrane involvement. These values are useful to guide fluid and electrolyte therapy. BUN and creatinine tests are indicated to screen for renal involvement and dehydration in cases of EM major requiring hospitalization.
Sedimentation rate is elevated but nonspecific.
Cultures are indicated in severe cases of EM major and should be obtained from blood, sputum, and mucosal lesions. No specific imaging studies are necessary in most cases. Chest x-ray may be useful in cases with respiratory symptoms or signs, particularly if an underlying pulmonary infection is suspected. Skin biopsy may be performed in equivocal cases when diagnosis is in doubt, particularly in absence of target lesions. Pathological findings include a predominantly inflammatory pattern characterized by a lichenoid infiltrate, which is high density and rich in T cells, and epidermal necrosis that mainly affects basal layer.