What is Panniculitis?
Panniculitis is a group of inflammatory diseases that affect the subcutaneous fat tissue. It often presents as tender, red nodules or plaques and can be associated with systemic symptoms such as fever, malaise, and weight loss. Histologically, panniculitis is characterized by inflammation of the subcutaneous adipose tissue and can be classified based on the predominant inflammatory infiltrate and the pattern of fat necrosis.
How is Panniculitis Classified?
Panniculitis is generally classified into two main types:
septal panniculitis and
lobular panniculitis. Septal panniculitis primarily involves the connective tissue septa that divide the fat lobules, while lobular panniculitis involves the fat lobules themselves. Each type can further be subdivided based on the presence of vasculitis.
What are the Histological Features of Septal Panniculitis?
In septal panniculitis, histological examination reveals inflammation along the septa of the fat lobules. The inflammatory infiltrate is often composed of lymphocytes, histiocytes, and sometimes
neutrophils. The hallmark of septal panniculitis is the absence of significant fat lobule involvement, although secondary involvement can occur. An example of septal panniculitis is
erythema nodosum, which is typically characterized by a mixed inflammatory infiltrate without vasculitis.
How is Vasculitis Involved in Panniculitis?
Vasculitis can be a component of both septal and lobular panniculitis. When present, it typically involves small vessels and can lead to more extensive tissue damage. The presence of vasculitis can complicate the clinical picture and often requires a different therapeutic approach. Histologically, vasculitis is identified by the presence of fibrinoid necrosis of vessel walls, endothelial swelling, and inflammatory cells within and around the vessel walls.
What are the Common Causes of Panniculitis?
The etiology of panniculitis can be diverse, ranging from infections and trauma to autoimmune diseases and malignancies. Common infectious causes include bacterial, fungal, and mycobacterial infections. Autoimmune diseases such as lupus erythematosus and
rheumatoid arthritis can also lead to panniculitis. Additionally, panniculitis can be associated with systemic diseases like sarcoidosis and specific conditions such as
Weber-Christian disease.
How is Panniculitis Diagnosed?
The diagnosis of panniculitis often involves a combination of clinical evaluation, imaging studies, and histopathological examination. A skin biopsy is essential for definitive diagnosis and should include both the dermis and subcutaneous tissue to adequately assess the inflammatory process. Special stains and immunohistochemical techniques may be employed to identify specific pathogens or immune complexes.
What are the Treatment Options for Panniculitis?
Treatment of panniculitis depends on the underlying cause. For infectious panniculitis, appropriate antimicrobial therapy is required. Inflammatory and autoimmune causes may respond to systemic corticosteroids, immunosuppressive agents, or biologics. Supportive care, including pain management and wound care, is also important. In some cases, treatment of the underlying systemic disease can lead to resolution of panniculitis.
Conclusion
Panniculitis represents a complex group of disorders with varied etiologies and histological presentations. Understanding the histopathological features is crucial for accurate diagnosis and effective treatment. By integrating clinical, histological, and sometimes molecular data, healthcare providers can better manage this challenging condition.
