Sources of trauma:
(1) occupational (manufacturing, farming, shipping, other)
(2) contact sports
(3) psychiatric disease with self-injury
(4) military service
(5) blunt accidental injury
Clinical history:
(1) repetitive blunt injury and/or pinching
(2) distribution of panniculitis in areas exposed to trauma
Histologic features:
(1) lobular panniculitis with neutrophilic infiltrate in acute lesions
(2) fat necrosis may occur with more intense blunt injury
(3) hemorrhage may be present, which is followed by hemosiderin deposition
(4) foreign body type giant cells, with polarizable material present if foreign material penetrates the epidermis
(5) areas of dystrophic calcification and fibrosis may be present as lesions resolve
(6) blunt injury in the overlying epidermis and dermis
Differential diagnosis:
(1) cellulitis or infectious panniculitis
(2) panniculitis following subcutaneous injections
(3) grease gun granuloma (see paraffinoma)
(4) cold panniculitis
(5) erythema nodosum (with blunt trauma to shins)
Some patients will have more than one cause (mixed panniculitis).
Diagnosis requires:
(1) exclusion of other causes when possible and
(2) documentation of the trauma history.
