Cutaneous Manifestations of Brucellosis
Brucellosis presents with cutaneous manifestations in approximately 1-14% of cases, most characteristically as a disseminated violet-erythematous papulonodular eruption, though ulcerative lesions, maculopapular rashes, and erythema nodosum-like lesions can also occur. 1, 2
Primary Cutaneous Presentations
Most Common Pattern
- Disseminated violet-erythematous papulonodular eruption is the most frequent cutaneous manifestation, occurring in approximately 74% of patients with skin involvement (20 of 27 cases in the largest prospective series) 2
- These lesions appear during the initial episode or during relapse of the disease 2
- The eruption is widespread and distinctive in appearance, helping differentiate brucellosis from other systemic infections 2
Other Documented Patterns
- Erythema nodosum-like lesions occur in approximately 11% of patients with cutaneous brucellosis 2
- Maculopapular rash can be the main presenting clinical feature, often accompanied by fever 1, 3
- Ulcerative lesions represent a rare but significant cutaneous manifestation that should prompt consideration of brucellosis, particularly in endemic areas 4
- Leukocytoclastic vasculitis has been documented on histopathology in patients with diffuse maculopapular rash 1
Histopathologic Features
The skin biopsy findings are relatively characteristic and support the diagnosis:
- Dermal inflammatory infiltrate composed of lymphocytes and histiocytes in a perivascular and periadnexal arrangement 2
- Focally granulomatous appearance with loose granuloma formation including giant cells 3, 2
- Occasional extension to subcutaneous fat 2
- These findings suggest hematogenous spread as the most important pathogenic mechanism 2
Clinical Context and Diagnosis
When to Suspect Cutaneous Brucellosis
- Any patient presenting with rash and fever in endemic areas should have brucellosis in the differential diagnosis 3
- History of consuming unpasteurized dairy products or occupational exposure to animals strengthens suspicion 5, 6
- The combination of characteristic skin lesions with systemic symptoms (fever, lymphadenopathy, hepatosplenomegaly) should prompt serologic testing 5
Diagnostic Confirmation
- Skin cultures can be positive for Brucella species (positive in 50% of attempted cases in one series) 2
- Blood cultures remain the gold standard, with positive results in the majority of cases with cutaneous manifestations 1, 2
- Standard tube agglutination test provides serologic confirmation 3
Treatment Response
- Cutaneous lesions heal quickly with standard antibiotic treatment (doxycycline 100 mg every 12 hours plus rifampicin 600 mg every 24 hours for 6 weeks) 6, 4
- The rapid resolution of skin findings with appropriate antimicrobial therapy supports the diagnosis retrospectively 4
Key Clinical Pitfall
The rarity of cutaneous manifestations (affecting only 1-14% of brucellosis patients) means they are often overlooked in the differential diagnosis of fever and rash. 1 However, when present, these skin findings can be the presenting feature that leads to diagnosis, particularly the characteristic violet-erythematous papulonodular pattern. 2 Failure to consider brucellosis in endemic areas or in patients with appropriate exposure history can delay diagnosis and treatment.