Panniculitis (inflammation of the subcutaneous fat) is a relatively uncommon condition that usually presents with inflammatory nodules or plaques. A wide variety of subtypes of panniculitis exist, including panniculitides related to infection, external insults, malignancy, and inflammatory diseases (table 1).
The diagnosis of panniculitis can be challenging because different forms of panniculitis may present with similar clinical findings and many types of panniculitis are rare. A careful clinical assessment that includes an evaluation of patient risk factors, lesion distribution, and associated clinical findings (eg, ulceration, sclerosis, atrophy) can provide valuable clues for diagnosis.
Although histopathologic examination of the affected area can be of benefit, interpretation of the biopsy findings must be approached with discretion. In the absence of careful clinical correlation and thorough consideration of the clinical and pathologic differential diagnoses, an incorrect diagnosis may be selected.
The approach to the recognition and diagnosis of panniculitis will be discussed here. The clinical features and management of specific forms of panniculitis are reviewed in greater detail separately.
The term panniculitis refers to a group of inflammatory disorders in which the primary site of inflammation is in the subcutaneous fat. In contrast, inflammatory disorders that mainly involve the overlying dermis or underlying fascia and incidentally extend into the nearby subcutaneous fat are not considered types of panniculitis.