Discuss the approach to use when attempting to diagnose an “unknown” case of panniculitis. - Careful history and physical examination are of greatest importance, emphasizing the location of the eruption, as well as its timing in relation to any possible drug ingestion, infection, or trauma.
- Laboratory studies should be guided by the clinical history but might include cultures of distant sites (e.g., for possible streptococcal pharyngitis in erythema nodosum), antinuclear antibody determination (to rule out lupus panniculitis), or measurement of a-1 antitrypsin levels (for evaluation of proteinase inhibitor–deficiency panniculitis).
- Skin biopsy can be of tremendous benefit, and recognition of established microscopic patterns of disease can be complemented by special stains and polarization microscopy.
- Immunohistochemistry can be useful in selected cases where malignancy is a possibility, and x-ray microanalysis is a specialized test that can be used to determine the identity of foreign material in cases of traumatic panniculitis.
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