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Infection-induced panniculitis
J W Patterson1, P C Brown, A H Broecker
1Department of Pathology, Medical College of Virginia, Richmond 23298.
Abstract:
We evaluated the histopathologic findings in 15 cases of panniculitis due to infection. Organisms were identified by special staining in 14 cases, and in 6 of these the etiologic agent was confirmed by culture studies. In one additional case, lesional culture was positive despite negative special staining. Eight cases were caused by gram positive or gram negative bacteria, 2 by atypical mycobacteria, 2 by Nocardia, and 3 by fungi (Candida and Fusarium species). Most patients had conditions or were receiving therapies predisposing to immunosuppression, but at least 2 individuals had no other major medical problems. There were some variability in microscopic findings and overlap with established forms of panniculitis; 3 cases (2 due to bacteria and 1 to Fusarium) resembled acute, "neutrophilic" erythema nodosum, and evidence of vasculitis was seen in septicemias due to Pseudomonas, Nocardia, and Fusarium. Nevertheless, several distinctive features associated with infectious panniculitis of diverse etiologies included: epidermal alterations such as acanthosis and parakeratosis; dermal edema with a diffuse or perivascular neutrophilic infiltrate; and mixed septal-lobular panniculitis with neutrophilic infiltration, vascular proliferation and hemorrhage, and necrosis. Infection should be suspected in virtually any case of panniculitis, particularly when occurring in an immunosuppressed patients, but the microscopic features enumerated above should arouse particular suspicion of an infectious process.
Insights
Infectious panniculitis can mimic other forms but presents with distinct histopathologic features. Suspect infection in panniculitis cases, especially in immunosuppressed patients, based on these microscopic findings.
Area of Science:
- Dermatopathology
- Infectious Diseases
Background:
- Panniculitis, inflammation of subcutaneous fat, can arise from various causes.
- Infectious agents are an underrecognized cause of panniculitis.
- Histopathologic evaluation is crucial for diagnosing the etiology of panniculitis.
Purpose of the Study:
- To characterize the histopathologic findings in infectious panniculitis.
- To identify features that distinguish infectious panniculitis from other forms.
- To emphasize the importance of considering infection in panniculitis cases.
Main Methods:
- Retrospective review of 15 cases of panniculitis with identified infectious agents.
- Histopathologic examination including special stains.
- Microbiologic culture studies for etiologic confirmation.
Main Results:
- Infectious agents identified in 14/15 cases by special stains and 6/15 by culture.
- Common causes included bacteria (8), atypical mycobacteria (2), Nocardia (2), and fungi (3).
- Distinctive features included epidermal alterations, dermal edema with neutrophilic infiltrate, and mixed septal-lobular panniculitis with vasculitis and necrosis.
Conclusions:
- Infectious panniculitis exhibits characteristic histopathologic features that can suggest an infectious etiology.
- Microscopic findings such as epidermal changes, neutrophilic infiltrate, and vasculitis warrant suspicion for infection.
- Infectious causes should be considered in all panniculitis cases, particularly in immunocompromised individuals.