Lab

• Elevated ESR
• CBC: Mild leukocytosis
• Antistreptolysin titers maybe elevated.
• Throat culture (usually negative because the infection typically resolves before lesions appear)
• Stool culture and leukocytes, if indicated
• Skin testing for mycobacteria, if indicated
• Drugs that may alter lab results: Antecedent antibiotics may affect cultures.

Imaging
CXR for hilar adenopathy or infiltrates related to sarcoidosis or tuberculosis

Diagnostic Procedures/Other
Deep skin excisional biopsy including subcutaneous fat; rarely necessary.

Pathological Findings

• Septal panniculitis
• Neutrophilic infiltrate in septa of fat tissue, early in course
• Fibrosis, paraseptal granulation tissue, lymphocytes, and multinucleated giant cells predominate late in course
• Lower dermis/subcutis involvement and septal fibrosis may occur.