Panniculitis describes a group of inflammatory conditions affecting the panniculus, the layer of fat directly beneath the skin. This subcutaneous fat provides insulation, stores energy, and protects from trauma. When inflamed, it causes various observable signs and internal symptoms. The characteristics of panniculitis vary depending on the underlying cause and type of inflammation.
Recognizing the Signs
Individuals experiencing panniculitis often notice tender, firm nodules or lumps that develop beneath the skin surface. These lesions typically appear as red, warm, and painful areas, ranging in size from small peas to several centimeters in diameter. While they can occur anywhere on the body, common locations include the shins, thighs, and forearms.
The skin overlying these nodules may appear discolored, often red or purplish, and can sometimes break down, leading to an ulcer or an oily discharge if the fat liquefies. Systemic symptoms may also occur, including low-grade fever, general feeling of unwellness, joint pain, muscle aches, and fatigue.
Common Forms and Underlying Factors
Panniculitis is a broad category of distinct disorders, each with unique characteristics and triggers. Conditions are often classified by the primary site of inflammation within the fat lobule (lobular, septal, or mixed patterns) and vasculitis. Many forms are idiopathic, but others link to identifiable factors.
One common form is Erythema Nodosum (EN), presenting as tender, red, warm nodules, mainly on the shins. EN is a septal panniculitis, affecting the connective tissue septa dividing fat lobules. Triggers include streptococcal infections, certain medications (e.g., oral contraceptives, sulfonamides), and systemic diseases like inflammatory bowel disease or sarcoidosis.
Lupus Panniculitis, also known as lupus profundus, is a less common type that occurs in some individuals with systemic lupus erythematosus (SLE). This form often presents with deep, firm nodules or plaques that can lead to atrophy and depressions in the skin as they heal. Inflammation in lupus panniculitis typically involves the fat lobules and can be associated with an autoimmune response targeting fat cells.
Pancreatic Panniculitis is a rare variant linked to diseases of the pancreas, such as pancreatitis or pancreatic cancer. In this condition, pancreatic enzymes released into the bloodstream can digest subcutaneous fat, leading to characteristic oily, red-brown nodules that may ulcerate.
Cold Panniculitis results from exposure to cold temperatures, often seen in infants or young children who have prolonged contact with cold surfaces. This type of panniculitis is characterized by firm, reddish plaques or nodules in areas exposed to cold, such as the cheeks or thighs. The cold temperature causes solidification of the subcutaneous fat, which then triggers an inflammatory response.
Alpha-1 Antitrypsin Deficiency-associated Panniculitis occurs in individuals with a genetic deficiency of the alpha-1 antitrypsin protein. This deficiency can lead to uncontrolled inflammation and destruction of fat tissue, presenting as tender, ulcerating plaques, often on the trunk or proximal extremities.
Diagnostic Approaches
Diagnosing panniculitis accurately often requires a comprehensive approach, as its clinical presentation can mimic other skin conditions. Diagnosis typically begins with a detailed medical history and a thorough physical examination, assessing the appearance, location, and characteristics of the skin lesions. The diagnostic process aims to identify the specific type of panniculitis and, if possible, its underlying cause.
The most definitive diagnostic tool for panniculitis is a skin biopsy. This procedure involves taking a small tissue sample from an affected area, examined under a microscope by a pathologist. Microscopic analysis reveals the specific pattern of inflammation—septal, lobular, or mixed—and the types of inflammatory cells involved.
Blood tests may be performed to support diagnosis and identify underlying conditions. These tests can include inflammatory markers such as erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP), which indicate systemic inflammation. Depending on the suspected cause, specific antibody tests for autoimmune diseases, enzyme levels for pancreatic function, or genetic tests for conditions like alpha-1 antitrypsin deficiency might also be conducted. Imaging studies, such as ultrasound or MRI, are less commonly used but may sometimes help assess the extent of fat involvement or rule out other conditions.
Treatment Strategies
Treatment for panniculitis is individualized, focusing on managing symptoms and addressing any identifiable underlying causes. When an underlying condition is identified, such as an infection or an autoimmune disease, treating that specific condition is often the primary approach. For instance, bacterial infections may require antibiotics, while managing inflammatory bowel disease can help resolve associated Erythema Nodosum.
For symptomatic relief, nonsteroidal anti-inflammatory drugs (NSAIDs) are used to reduce pain and inflammation associated with the nodules. Rest and elevation of affected limbs can also help decrease discomfort and swelling. Local care for skin lesions, especially if they ulcerate, involves wound management to prevent infection and promote healing.
In cases where the panniculitis is severe, persistent, or associated with significant systemic symptoms, stronger medications may be necessary. Corticosteroids, which are anti-inflammatory agents, can be administered orally or sometimes injected directly into the lesions to reduce inflammation. Immunosuppressive therapies, such as methotrexate or azathioprine, may be considered for chronic or recurrent forms of panniculitis that do not respond to other treatments, especially when an autoimmune basis is suspected.