Can brucellosis mimic tuberculosis?

Can Brucellosis Present or Mimic Tuberculosis?

Yes, brucellosis frequently mimics tuberculosis with remarkable clinical, laboratory, and radiological overlap, making differentiation extremely challenging, particularly in regions where both diseases are endemic. 1

Clinical Overlap

The clinical presentations of brucellosis and tuberculosis share multiple features that make differentiation difficult:

Constitutional Symptoms

• Chronic fever occurs in approximately 65% of brucellosis patients, often with evening temperature rises (34%) and night sweats (16%), which are classic TB symptoms 1
• Significant weight loss affects 25% of brucellosis patients, mimicking the wasting syndrome typical of tuberculosis 1
• Productive cough is present in 40% of brucellosis cases, despite normal respiratory examination findings, creating confusion with pulmonary TB 1
• Approximately 28% of brucellosis patients present with at least three classic TB symptoms simultaneously 1

Physical Examination Findings

• Hepatosplenomegaly occurs in 25-47% of brucellosis cases, which can also be seen in disseminated TB 1, 2
• Lymphadenopathy is present in 15-22% of brucellosis patients, overlapping with TB lymphadenitis 1, 2
• The combination of fever, organomegaly, and lymphadenopathy creates a clinical picture indistinguishable from extrapulmonary TB 1

Laboratory Mimicry

Inflammatory Markers

• Markedly elevated ESR (>50 mm/hr) occurs in 25% of brucellosis cases, with 16% exceeding 100 mm/hr, levels typically associated with active TB 1
• Hypergammaglobulinemia is present in 25% of brucellosis patients, another feature commonly seen in chronic TB 1

Hematologic Abnormalities

• Anemia affects 57% of brucellosis patients 2
• Both leucopenia (15%) and leucocytosis (15%) can occur, similar to TB 2
• Thrombocytopenia is present in 34% of cases 2

Histopathologic Confusion

• Non-caseating granulomas appear in bone marrow biopsies in approximately 9% of brucellosis cases, which can be misinterpreted as TB, though TB typically shows caseating granulomas 1
• Lymph node biopsies may show granulomatous inflammation in both diseases 1

Pleural Involvement

When brucellosis affects the pleura (though rare), it is remarkably difficult to differentiate from tuberculous pleurisy:

• Pleural fluid analysis shows exudative effusions with lymphocyte predominance, decreased glucose concentration, and elevated adenosine deaminase (ADA) levels, all classic features of TB pleurisy 3
• The British Thoracic Society notes that TB pleurisy may mimic other conditions with complex septated effusions on ultrasound 4

Extrapulmonary Manifestations

Focal complications of brucellosis are particularly difficult to distinguish from extrapulmonary TB:

Vertebral Osteomyelitis

• Both diseases cause vertebral involvement with similar radiologic appearances 5
• Clinical presentation with back pain, fever, and elevated inflammatory markers is identical 5

Meningitis/Meningoencephalitis

• Subacute or chronic meningitis occurs in both diseases 5
• CSF findings may overlap significantly 6

Arthritis

• Both cause chronic arthritis affecting large joints 7
• Brucellosis can cause septic arthritis of the knee with fever, requiring definitive exclusion of infection 7

Abdominal Involvement

• Liver and splenic abscesses occur in both diseases 5
• The World Society of Emergency Surgery notes that abdominal TB has variable, non-specific presentation that may mimic other infectious diseases 4

Critical Clinical Pitfall

The most dangerous consequence of this overlap is the potential for developing drug-resistant tuberculosis when brucellosis is misdiagnosed as TB:

• Rifampicin is used in both brucellosis and TB treatment regimens 6
• If brucellosis is mistakenly treated as TB monotherapy or with inadequate regimens, this can lead to rifampicin-resistant TB 1
• It is essential to definitively rule out tuberculosis in all cases of suspected or proven brucellosis before initiating antimicrobial therapy 1

Diagnostic Approach

When to Suspect Brucellosis Over TB

• History of contact with unpasteurized dairy products or infected animals (present in 65% of brucellosis cases) 2
• Occupational exposure to livestock, as recommended by the CDC for prevention strategies 6
• Geographic location in brucellosis-endemic regions 6

Definitive Differentiation

• Blood or body fluid cultures using BACTEC method remain the gold standard for brucellosis diagnosis 2
• Brucella agglutinins with titers ≥1:320 are considered significant 2
• Multiplex real-time PCR targeting both organisms simultaneously has 93% sensitivity, 100% specificity, and 96% accuracy for differential diagnosis, representing the most rapid and reliable method 8, 5
• Conventional microbiological methods for both diseases are time-consuming and have significant limitations 8, 5

Geographic Considerations

In countries like India and other regions where both diseases are endemic, rapid, sensitive, and highly specific diagnostic methods are required to make early diagnosis and prevent resistance 2. The overlap in clinical presentation, laboratory findings, and even histopathology makes empiric treatment decisions particularly hazardous in these settings 1.