Tuberculosis !

Tuberculosis is a bacterial infection spread through the air that mainly affects the lungs but can reach almost any organ, including the spine and lymph nodes.

Updated 2026-10-30

Structures involved

Tap one to see what it is and open it in 3D.

In biochemistry

Microorganisms that cause it

In immunology

In histology

In embryology

Tetracyclines and aminoglycosides

In the clinical exam

Lymph node examination

In physiology

CSF and the blood–brain barrier

Why it happens

Show 3 more

What it is

An infection caused by Mycobacterium tuberculosis, spread through the air, that mainly affects the lungs but can involve almost any organ, including the spine, lymph nodes and meninges.

Who gets it

One of the leading infectious causes of death worldwide. It remains a public-health problem in Colombia and Latin America, especially in prisons, poor urban areas, Indigenous communities and people with HIV. In shanty towns of Callao, Peru, 9% of 2,666 household contacts aged 15 or older developed tuberculosis over about 10 years of follow-up (2002–2016).

Causes

Mycobacterium tuberculosis complex
Airborne droplet nuclei from a person with active pulmonary TB
Reactivation of latent infection
Rarely: M. bovis from unpasteurized milk

Risk factors

HIV infection
Close contact with a person with active TB
Diabetes, malnutrition, smoking, alcohol use
Immunosuppressive drugs, including TNF inhibitors and corticosteroids
Crowded settings: prisons, shelters
Young children and older adults

Pathophysiology

Inhaled bacilli are taken up by alveolar macrophages and survive inside them. Cell-mediated immunity forms granulomas with caseous necrosis that usually contain the infection (latent TB). If immunity weakens, bacilli multiply, cavities form in the lung and bacilli spread through blood or lymph to other organs.

Classification

Latent TB infection
Active pulmonary TB
Extrapulmonary TB: lymph node, pleural, spinal (Pott disease), meningeal, abdominal, genitourinary
Miliary (disseminated) TB
Drug-susceptible versus drug-resistant (MDR, XDR)

Symptoms and signs

Cough for more than two weeks, sometimes with blood
Fever, night sweats and weight loss
Fatigue and loss of appetite
Lymph node TB: painless, matted neck nodes that may drain (scrofula)
Pott disease: back pain, local tenderness, spinal deformity (gibbus)
Meningeal TB: subacute headache, fever, confusion, cranial nerve palsies

Diagnosis

Clinical: Prolonged cough, fever, night sweats and weight loss, especially with TB contact or HIV; extrapulmonary forms suspected by the organ involved.
Tests: Sputum smear microscopy, culture and rapid molecular tests (nucleic acid amplification) that also detect rifampicin resistance. Tuberculin skin test or interferon-gamma release assay for latent infection. Biopsy or fluid sampling (node, CSF, pleura) for extrapulmonary TB; HIV test for everyone.
Imaging: Chest X-ray: upper-lobe infiltrates, cavities, hilar nodes, effusion or miliary pattern. MRI of the spine in Pott disease (vertebral and disc destruction, paraspinal or psoas abscess); brain MRI in meningeal TB.

Differential diagnosis

Lung cancer
Bacterial pneumonia or lung abscess
Lymphoma
Spinal metastases or pyogenic spondylodiscitis
Fungal infections (histoplasmosis, paracoccidioidomycosis)
Sarcoidosis

Goal of treatment

Cure the infection with a full course of combination therapy, prevent drug resistance, stop transmission and preserve organ function, especially of the spine and brain.

Treatment

Medical: Drug-susceptible TB: several months of combined first-line antituberculosis drugs (isoniazid, rifampicin, pyrazinamide and ethambutol), with longer courses for meningeal and spinal TB as guidelines advise.
Follow-up: Directly observed therapy, sputum checks and follow-up for drug toxicity, especially of the liver.
Medical: Drug-resistant TB: regimens of second-line drugs guided by resistance testing, under specialist care.
Medical: TB meningitis: corticosteroids are added to reduce inflammation.
Surgical: Pott disease: surgery for spinal cord compression, instability, deformity or abscess drainage when drugs alone are not enough.

Drugs for this condition

Complications

Drug-resistant TB
Spinal deformity and paraplegia (Pott disease)
Hydrocephalus, stroke and lasting neurological damage (TB meningitis)
Massive hemoptysis and lung scarring
Pleural empyema
Adrenal insufficiency

Prognosis

Drug-susceptible TB is curable in most patients who complete treatment. Outcomes are worse with drug resistance, HIV, late diagnosis and meningeal disease.

Prevention

BCG vaccine at birth, which mainly protects young children from severe forms (miliary TB and TB meningitis)
Early diagnosis and complete treatment of active cases
Contact tracing and preventive treatment of latent infection
Ventilation and infection control in health care and crowded settings
HIV testing and ART

Test yourself

Think of the answer, then tap the question to see it.

What is Pott disease and which part of the spine does it usually affect?

Tuberculous spondylitis: infection of the vertebrae and discs, most often the lower thoracic and upper lumbar spine, which can cause gibbus and cord compression.

What does BCG vaccination mainly protect against?

Severe childhood forms of TB, especially miliary TB and TB meningitis; protection against adult pulmonary TB is variable.

How is latent TB distinguished from active TB?

Latent TB: positive tuberculin skin test or IGRA with no symptoms and normal chest imaging, not contagious. Active TB: symptoms, abnormal imaging and/or positive microbiology.

What is the typical appearance of tuberculous cervical lymphadenitis (scrofula)?

Painless, slowly enlarging, matted neck lymph nodes that may soften and drain through the skin.

What kind of rapid test detects M. tuberculosis and rifampicin resistance at the same time?

Rapid molecular tests based on nucleic acid amplification, which detect the bacillus and mutations linked to rifampicin resistance.

Add to my cards (5)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: Tuberculosis Overview (StatPearls (NCBI Bookshelf), 2024); Active and passive case-finding in tuberculosis-affected households in Peru: a 10-year prospective cohort study (The Lancet. Infectious diseases, 2019) · adapted, CC BY 4.0.

← All conditions

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.

Right upper lobe highlighted on the Durgical 3D model