Clinical Pearls for Differentiating Disseminated Granulomatous Diseases

Geographic and Exposure History

The American College of Physicians suggests that geographic exposure is the single most important initial differentiator and should guide the entire diagnostic approach 1
Histoplasmosis is endemic to Ohio and Mississippi River valleys, with occupational exposure to bird/bat droppings, or cave exploration 3, 4, 1
Tuberculosis is associated with recent travel to or residence in TB-endemic regions, close contact with active TB cases, or congregate living settings 1
Brucellosis is linked to occupational exposure to livestock, consumption of unpasteurized dairy products, or endemic regions 5, 1
Leishmaniasis is associated with travel to endemic areas or sandfly exposure 5, 6
Sarcoidosis has a higher incidence in northern Europeans and African Americans, with no specific exposure pattern 7, 1

Brucellosis is characterized by an undulating fever pattern with profound sweats and arthralgias, which is highly characteristic 5, 1
TB and Histoplasmosis typically present with chronic fever, night sweats, weight loss, and extreme fatigue lasting weeks to months 5, 4, 1
Leishmaniasis (visceral) presents with chronic fever, weight loss, splenomegaly, pancytopenia, hypoalbuminemia, and elevated acute inflammatory markers 5, 6
Lymphoma is associated with B symptoms (fever, night sweats, weight loss) plus painless lymphadenopathy 1
Sarcoidosis may be asymptomatic or present with Löfgren's syndrome, which is pathognomonic 7, 1

Sarcoidosis is characterized by bilateral hilar adenopathy with perilymphatic nodules and upper lobe predominance 7, 1, 2
TB/Histoplasmosis typically show necrotizing granulomas with cavitation, tree-in-bud pattern, and upper lobe predominance 3, 4, 1, 2
Lymphoma is associated with bulky mediastinal adenopathy, extranodal masses, and anterior mediastinal involvement 1

TB is characterized by robust, frequent necrotizing granulomas with central caseous necrosis and AFB stain positive 1, 2
Histoplasmosis shows large acellular necrotizing granulomas with GMS/PAS stains positive for small intracellular yeast forms 3, 4, 1, 2
Brucellosis is associated with non-caseating granulomas, similar to sarcoidosis, but with positive cultures or serology 1
Sarcoidosis is characterized by well-formed, non-necrotizing granulomas in perilymphatic distribution with minimal surrounding lymphocytic inflammation 7, 1, 2
Lymphoma shows a monoclonal B-cell population on immunohistochemistry, flow cytometry shows clonality, and absence of true granulomas 1

The American Thoracic Society recommends that mycobacterial testing, including sputum/tissue AFB smear and culture, should be performed first 1
Fungal testing, including urine and serum antigen for Histoplasma, should be performed simultaneously 3, 4, 1
Brucellosis testing, including blood cultures and serology, should be performed if there is exposure history 1, 5
Leishmaniasis testing, including bone marrow aspiration and serology, should be performed if there is geographic exposure 5, 8
Sarcoidosis-specific testing, including serum ACE level and CD4/CD8 ratio in BAL fluid, should be performed only after excluding infection 7, 2

The Infectious Diseases Society of America warns that necrotizing granulomas can occur in sarcoidosis variants, not exclusively in infections 2
Negative AFB stain does not exclude TB, and culture and molecular testing are required 2
Immunocompromised patients have atypical presentations of all these diseases with higher dissemination risk 5, 6
Leishmaniasis in HIV patients may present with atypical skin lesions, and parasites can be found in unusual sites 5, 6
Brucellosis granulomas are non-caseating, indistinguishable from sarcoidosis histologically, and diagnosis requires positive culture or serology 1