Lupus panniculitis (LP), also known as lupus profundus, is a chronic inflammatory condition that targets the subcutaneous fat layer directly beneath the skin. This autoimmune condition causes localized damage to the body’s fatty tissue. LP is a relatively rare manifestation of lupus erythematosus. As a subtype of cutaneous lupus erythematosus, LP can occur independently or in conjunction with other forms, such as Discoid Lupus Erythematosus (DLE) or Systemic Lupus Erythematosus (SLE).
Clinical Presentation and Physical Characteristics
The defining feature of lupus panniculitis is the presence of firm, indurated, and often tender nodules that develop deep within the subcutaneous tissue. These palpable lesions range in size from a pea to several centimeters across. They frequently appear on areas where fat is most prominent, including the proximal upper arms, thighs, buttocks, and face.
The skin overlying these deep nodules may appear normal, or it can present with redness, inflammation, or classic lesions of DLE. These painful nodules typically follow a cycle of flare-ups and periods of remission. Severe inflammation can sometimes cause ulceration, where the skin breaks open.
When the active inflammatory phase subsides, the damaged fat tissue is reabsorbed. This process leads to the formation of depressed, hardened areas in the skin contour. These physical changes are a direct result of the destructive inflammation and highlight the need for prompt management.
Confirming the Diagnosis
Diagnosing lupus panniculitis requires a combination of clinical suspicion and laboratory confirmation because its presentation can mimic other types of inflammation in the fat tissue. The most definitive step in the diagnostic process is performing a deep skin biopsy of the affected lesion. Due to the depth of the inflammation, an excisional biopsy is often preferred over a standard punch biopsy to ensure an adequate sample of the subcutaneous fat is obtained.
Under the microscope, the characteristic histological pattern is a lymphocytic lobular panniculitis. This means the inflammation is concentrated primarily within the fat lobules, consisting of a dense infiltration of immune cells, including lymphocytes and plasma cells. Specific findings also include hyaline fat necrosis and the presence of lymphoid nodules, which help distinguish LP from other forms of panniculitis.
Blood tests can provide supportive evidence for a lupus diagnosis. For example, tests for Antinuclear Antibodies (ANA) may be positive, although this is not specific to LP, and a negative ANA test does not rule out the condition.
Management and Therapeutic Approaches
The primary goal of managing lupus panniculitis is to suppress the inflammation to relieve symptoms and prevent the irreversible loss of subcutaneous fat. Treatment often follows a stepwise approach, adjusting therapy based on the extent and severity of the lesions.
For lesions that are localized and not widespread, the initial therapeutic strategy may involve the use of corticosteroids. Corticosteroids can be delivered directly into the lesions through intralesional injection to concentrate the anti-inflammatory effect at the site of disease activity.
For more extensive or persistent disease, systemic therapy becomes necessary to control the underlying autoimmune process. Antimalarial medications, particularly hydroxychloroquine, are considered the first-line systemic treatment for LP. If the disease proves refractory, meaning it does not respond adequately to antimalarials, a physician may escalate treatment to stronger immunosuppressive agents such as methotrexate, azathioprine, or mycophenolate mofetil.
Relationship to Systemic Lupus and Long-Term Outcomes
Lupus panniculitis is a manifestation of chronic cutaneous lupus erythematosus, representing a relatively small fraction of all cutaneous lupus cases. It can be the first sign of a lupus disorder, or it may occur in individuals who already have a diagnosis of DLE or SLE. The activity of LP lesions does not always directly mirror the activity or severity of any coexisting systemic lupus.
The most significant and long-lasting consequence of LP is lipoatrophy, which is the permanent destruction and loss of the subcutaneous fat tissue. As the active inflammatory nodules heal, they leave behind depressed, cup-shaped areas on the skin surface.
This resulting disfigurement and permanent scarring can significantly impact a patient’s quality of life, especially when the lesions occur on the face or other highly visible areas. Treatment for established lipoatrophy may require cosmetic interventions, such as soft tissue fillers or autologous fat grafting, to restore contour to the depressed areas. Addressing the underlying inflammation early remains the most effective strategy to minimize these permanent physical changes.