Diagnostic Considerations
Tuberculosis (TB) is well known for its ability to masquerade as other infectious and disease processes. For example, congenital TB can mimic congenital syphilis or cytomegalovirus (CMV) infection. Along with the differentials listed in the next section, conditions with a presentation that may resemble pulmonary TB include the following:
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Blastomycosis
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Tularemia
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Actinomycosis
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Mycobacterium avium-intracellulare infection
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M chelonae infection
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M fortuitum infection
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M gordonae infection
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M kansasii infection
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M marinum infection
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M xenopi infection
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Squamous cell carcinoma
Conditions to be included in the differential diagnosis of extrapulmonary TB include the following:
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Blastomycosis
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Tularemia
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Actinomycosis
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Hidradenitis suppurativa
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Eosinophilic granuloma
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M avium-intracellulare infection
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M chelonae infection
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M fortuitum infection
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M gordonae infection
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M kansasii infection
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M marinum infection
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M xenopi infection
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Endemic syphilis
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Erythema induratum (nodular vasculitis)
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Erythema nodosum
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Leishmaniasis
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Leprosy
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Cat scratch disease
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Syphilis
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Syringoma
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Rheumatoid arthritis
Dermatologic differential diagnosis
Diagnosis of skin infection with M tuberculosis involves the following:
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Differentiate primary-inoculation TB from ulceroglandular complexes and mycobacterioses
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Differentiate TB verrucosa cutis from diseases such as North American blastomycosis, chromoblastomycosis, iododerma and bromoderma, chronic vegetative pyoderma, verruca vulgaris, verrucous carcinoma, verrucous atypical mycobacterial infection, and verrucous lupus vulgaris
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Differentiate miliary TB of the skin (which appears as small, noncharacteristic, erythematous, papular or purpuric lesions) from drug reactions
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Differentiate scrofuloderma from suppurative lymphadenitis with sinus-tract formation, such as blastomycosis or coccidioidomycosis
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Differentiate TB cutis orificialis from glossitis, apotheosis, and deep fungal infections
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Differentiate lupus vulgaris from lupoid rosacea, deep fungal or atypical mycobacterial infection, chronic granulomatous disease, granulomatous rosacea, and Wegener granulomatosis
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Differentiate erythema induratum from nodular panniculitides (eg, Weber-Christian disease) and nodular vasculitides (eg, syphilitic gumma, nodular pernio)
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Differentiate papulonecrotic tuberculid from other papulonecrotic entities, such as leukocytoclastic vasculitis, lymphomatoid papulosis, papular eczema, and prurigo simplex with neurotic excoriation
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Differentiate lichen scrofulosorum from keratosis spinulosa, lichenoid sarcoid, and lichenoid secondary syphilis
Differential Diagnoses
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Acid-fast bacillus smear showing characteristic cording in Mycobacterium tuberculosis.
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This radiograph shows a patient with typical radiographic findings of tuberculosis.
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This is a chest radiograph taken after therapy was administered to a patient with tuberculosis.
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Anteroposterior chest radiograph of a young patient who presented to the emergency department (ED) with cough and malaise. The radiograph shows a classic posterior segment right upper lobe density consistent with active tuberculosis. This woman was admitted to isolation and started empirically on a 4-drug regimen in the ED. Tuberculosis was confirmed on sputum testing. Image courtesy of Remote Medicine (remotemedicine.org).
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Lateral chest radiograph of a patient with posterior segment right upper lobe density consistent with active tuberculosis. Image courtesy of Remote Medicine (remotemedicine.org).
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Pulmonary tuberculosis with air-fluid level.
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Under a high magnification of 15549x, this scanning electron micrograph depicts some of the ultrastructural details seen in the cell wall configuration of a number of Gram-positive Mycobacterium tuberculosis bacteria. As an obligate aerobic organism, M. tuberculosis can only survive in an environment containing oxygen. This bacterium ranges in length between 2-4 microns, with a width between 0.2-0.5 microns. Image courtesy of the Centers for Disease Control and Prevention/Dr. Ray Butler.
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Numerous acid-fast bacilli (pink) from a bronchial wash are shown on a high-power oil immersion.
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Necrotizing granuloma due to tuberculosis shown on low-power hematoxylin and eosin stain. There is central caseous necrosis and a multinucleated giant cell in the central left. Mixed inflammation is seen in the background.
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This chest radiograph shows asymmetry in the first costochondral junctions of a 37-year-old man who presented with cough and fever. Further clarification with computed tomography is needed.
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Axial noncontrast enhanced computed tomography with pulmonary window shows a cavity with an irregular wall in the right apex of a 37-year-old man who presented with cough and fever (same patient as above).
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Coronal reconstructed computed tomography image shows the right apical cavity in a 37-year-old man who presented with cough and fever (same patient as above).
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This posteroanterior chest radiograph shows right upper lobe consolidation with minimal volume loss (elevated horizontal fissure) and a cavity in a 43-year-old man who presented with cough and fever.
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Axial chest computed tomography without intravenous contrast with pulmonary window setting shows a right apical thick-walled cavity and surrounding lung consolidation in a 43-year-old man who presented with cough and fever (same patient as above).
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Coronal reconstructed computed tomography image shows the consolidated, partially collapsed right upper lobe with a cavity that is directly connected to a bronchus in a 43-year-old man who presented with cough and fever (same patient as above).
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The posteroanterior chest radiograph shows a large cavity with surrounding consolidation in the lingular portion of the left upper lobe in a 43-year-old man who presented with cough and hemoptysis. There are also a few nodular opacities in the right mid-lung zone.
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Axial chest computed tomography without intravenous contrast with pulmonary window setting through the mid-chest shows a large, irregular-walled cavity with nodules and air-fluid level and two smaller cavities in a 43-year-old man who presented with cough and hemoptysis (same patient as above). Small, patchy peripheral opacities are also present in the left lower lobe. In the right mid-lung, nodular opacities are in a tree-in-bud distribution, suggestive of endobronchial spread.
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Coronal reconstructed computed tomography image shows the lingular cavity with irregular nodules and right mid-lung nodular opacities in a 43-year-old man who presented with cough and hemoptysis (same patient as above).
