TUBERCULOSIS

✓ Medically ReviewedDISEASEID: MDBT0145🚨 TRIAGE: URGENTICD-10: A15

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Definition

CLINICAL DEFINITION

Tuberculosis is chronic bacterial infection caused by Mycobacterium tuberculosis complex (slow-growing acid-fast bacilli). It spreads by airborne droplets (tiny particles breathed from coughing) from pulmonary cases. It most often affects lungs with cough, fever and weight loss. It can affect nodes (glands), pleura (lung lining), bones, kidneys and meninges (brain coverings). Latent infection is dormant without symptoms while active disease causes illness and spread.

IN PLAIN ENGLISH

TB is a lung germ that spreads by cough. It grows very slowly in the body. Many carry it asleep with no illness. Active TB causes cough, fever and weight loss. It needs many months of drugs to cure.

COMMON MISCONCEPTION / WHAT IT DOES NOT MEAN

Tuberculosis is not nontuberculous mycobacterial disease (environmental mycobacteria needing different drugs) alone. It is not latent infection without illness needing the same urgency as active disease. It is not simple bacterial pneumonia (short lung infection) that resolves with days of antibiotics. It is not sarcoidosis (immune granuloma disease) or lung cancer (malignant growth) despite similar scans.

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Word Breakdown

tubercul-

=little swelling meaning granuloma nodule

-osis

=condition meaning chronic disease process

Literal Meaning: condition of little lumps

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Abbreviations

TB=Tuberculosis - chronic bacterial infection usually of lungs

LTBI=Latent TB infection - dormant infection without symptoms where latent means hidden

MDR-TB=Multidrug-resistant TB - resistant to isoniazid and rifampicin where resistant means drugs fail

XDR-TB=Extensively drug-resistant TB - MDR plus fluoroquinolone plus bedaquiline or linezolid resistance

DOT=Directly observed therapy - watched dosing to secure completion

BCG=Bacille Calmette-Guerin - live vaccine against severe childhood TB

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Synonyms & Variants

Consumption›Phthisis›White plague›

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Category-Specific Context

Tuberculosis is a Disease because it is a distinct infection with cause, course and cure. It is not a single Symptom (patient complaint) or Sign (exam finding). It has latent and active stages with drug-resistance patterns. Management uses months of combination therapy with contact tracing. It needs public-health notification with long follow-up.

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Clinical Context & Usage

CLINICAL SETTINGS

Chest and TB ClinicInfectious Diseases Outpatient ServicePrimary Care for Chronic CoughEmergency Department for HaemoptysisPublic Health Contact Tracing ClinicPaediatric Clinic for Household Contacts

USAGE & DOCUMENTATION NOTES

Use tuberculosis for confirmed disease or high suspicion pending tests. Specify site such as pulmonary, lymph node, pleural, spinal or meningeal. State drug pattern such as susceptible, multidrug-resistant or extensively drug-resistant when known. Do not label latent infection as active disease. Record smear, molecular test, culture, HIV status and contacts each visit.

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Primary Causes & Pathophysiology

PATHOPHYSIOLOGY

Inhaled droplet nuclei (tiny airborne particles) reach alveoli (air sacs). Alveolar macrophages (lung eater cells) engulf bacilli but often fail to kill them. T cells (immune fighter cells) wall off foci into granulomas (rounded immune nests) with caseation (cheese-like necrosis). Ghon focus (healed lung focus) with hilar node (central chest gland) forms primary complex. Weak immunity allows liquefaction (tissue breakdown) with cavitation (hole formation) and spread.

PRIMARY CAUSES

Mycobacterium tuberculosis airborne exposure

Inhaled bacilli infect alveoli and persist in macrophages causing granulomas that later cavitate and spread

Prolonged close contact with infectious pulmonary case

Repeated droplet exposure in crowded or poorly ventilated rooms raises inhaled dose and infection risk

HIV infection with low CD4 count (immune cell count)

Lost T-cell control allows latent foci to reactivate and new infection to disseminate rapidly

Diabetes mellitus with poor glycaemic control (high sugar control)

Impaired macrophage and T-cell function weakens granuloma walls favouring reactivation

Silicosis and other dust lung disease

Damaged macrophages with fibrotic lungs (scarred lungs) cannot contain bacilli so foci progress

Malnutrition with crowding and poor ventilation

Weak immunity plus high exposure dose allows infection to establish and progress to disease

Immunosuppression from tumour necrosis factor blockers, steroids or dialysis

Blocked granuloma signalling dissolves containment and releases dormant bacilli

Mycobacterium bovis zoonotic exposure via unpasteurised milk

Ingested or inhaled bovine bacilli cause lymph node and gut disease similar to tuberculosis

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Epidemiology

Prevalence:Tuberculosis remains one of the top infectious killers worldwide. WHO estimates about 10 million new cases each year. Highest burden sits in South-East Asia, Africa and Western Pacific regions. HIV coinfection concentrates in parts of Africa.

Age Group:All ages can develop tuberculosis. Young adults carry high pulmonary burden. Children face higher risk of disseminated and meningeal disease after exposure. Older adults face reactivation from waning immunity with comorbid illness.

Geographic Distribution:Tuberculosis occurs worldwide in all regions. Burden is highest in South-East Asia, Africa and Western Pacific per WHO reports. HIV coinfection clusters where HIV prevalence is high. No climate restriction applies because spread is person to person.

Red Flags & Triage ★

TRIAGE LEVEL

🚨 URGENT

DO NOT MISS — LIFE-THREATENING PRESENTATIONS

Multidrug-resistant disease needing rapid molecular resistance test
HIV coinfection needing antiretroviral timing
TB meningitis needing urgent lumbar puncture (spinal fluid test) and steroids
Household child contacts needing preventive therapy
Liver injury with visual upset on ethambutol (eye drug)

URGENT EVALUATION TRIGGERS

Haemoptysis with breathlessness or low oxygen
Neck stiffness with fever, headache or confusion suggesting meningitis
Back pain with weakness or numbness suggesting spinal disease
Severe weight loss with night sweats and prolonged cough
Known exposure with new fever or cough in a child contact
Vomiting with jaundice or visual change on therapy

Contraindications & Precautions

CONTRAINDICATIONS

Do not treat active tuberculosis with a single drug because resistance emerges fast
Do not use fluoroquinolone monotherapy for pneumonia before excluding tuberculosis where risk is high
Do not stop therapy early when feeling better because relapse and resistance follow
Do not give live BCG vaccine during severe immunosuppression (weak immunity)

SPECIAL PRECAUTIONS

Isolate infectious pulmonary cases with airborne precautions and notify public health
Trace household and close contacts with screening and preventive therapy
Test HIV with diabetes, check liver function and vision during therapy
Use directly observed therapy with adherence support and pyridoxine (vitamin B6) where indicated
Monitor sputum conversion with culture and resistance testing

Complications

DOWNSTREAM CLINICAL COMPLICATIONS

Lung cavitation with haemoptysis (coughing blood) and breathlessness
Pleural effusion (fluid around lung) with empyema (pus around lung)
Miliary spread (widespread millet-seed lesions) to many organs
TB meningitis (brain-cover infection) with hydrocephalus (fluid buildup)
Pott spine (spinal TB) with collapse and cord compression
Pericardial TB with constriction (stiff heart sac)
Treatment-related liver injury with adherence failure and resistance

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Confused With (LASA & DDx) ★

LEXICAL (LASA) — SIMILAR NAMES

Nontuberculous mycobacterial infection

Shares mycobacteria and lung nodules but means environmental species needing different drugs

Sarcoidosis

Shares granulomas and hilar nodes but means sterile immune disease without bacilli

Nocardiosis

Shares chronic nodules with acid-fast staining but means Nocardia bacteria needing sulfonamide therapy

CLINICAL DIFFERENTIAL DIAGNOSES (DDx)

Community-acquired pneumonia

Key Distinguishing Feature: Acute fever with lobar consolidation (single lobe filling) that responds to days of antibiotics

Primary lung cancer

Key Distinguishing Feature: Focal mass with weight loss in smokers without response to TB therapy

Sarcoidosis

Key Distinguishing Feature: Symmetric hilar nodes with skin or eye disease and no bacilli on tests

Nontuberculous mycobacterial lung disease

Key Distinguishing Feature: Bronchiectasis with repeated environmental isolates and different drug needs

Pulmonary fungal infection

Key Distinguishing Feature: Travel or cave exposure with fungal serology (fungus blood test) and no mycobacteria

Lung abscess from aspiration

Key Distinguishing Feature: Putrid sputum (foul sputum) with air-fluid level that responds to anaerobic cover

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Clinical Pearls

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Isolate possible pulmonary TB at once with airborne room, mask and public-health notification and do not wait for culture.

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Test sputum with rapid molecular assay (Xpert) plus HIV in every suspected case because resistance and coinfection change plans.

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Give weight-based 2 months of isoniazid, rifampicin, pyrazinamide and ethambutol then 4 months of isoniazid and rifampicin with observed dosing for susceptible disease.

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Add pyridoxine (vitamin B6) with isoniazid in pregnancy, diabetes, alcohol use or malnutrition to prevent neuropathy (nerve tingling).

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Add corticosteroids (anti-inflammatory steroids) for meningitis and pericardial disease per guideline while continuing full TB drugs.

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Example Usage & SOAP

CLINICAL SENTENCE

""32-year-old with 3-week cough, night sweats and cavitary lesion has pulmonary tuberculosis.""

IN A SOAP NOTE

S: 32-year-old man with 3-week productive cough, night sweats and 4 kg loss, household TB contact last year. O: Temp 38.1C, BP 118/74, HR 98, RR 20, SpO2 95 percent on air, right upper crackles with weight 58 kg, no meningism. A: Likely pulmonary tuberculosis needing isolation and rapid tests. P: Airborne isolation with notification, sputum smear plus Xpert with culture, chest film, HIV and HbA1c, start weight-based 4-drug therapy with DOT referral.

DIFFERENTIAL DIAGNOSIS CONTEXT

Chronic cough with upper-lobe cavitation favours tuberculosis over acute bacterial pneumonia. Acute lobar consolidation (single lobe filling) with rapid antibiotic response favours bacterial pneumonia. Symmetric hilar nodes without bacilli favour sarcoidosis. Bronchiectasis with repeated environmental isolates favours nontuberculous disease. Test sputum molecular assay with culture and HIV.

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Classifications & Scoring

GRADING SYSTEM

Sputum smear microscopy grading

Grades acid-fast bacilli from scanty to 3 plus to reflect bacillary load and infectiousness

STAGING SCALE

Clinical spectrum staging of tuberculosis

Stages as latent infection, active pulmonary, extrapulmonary, miliary and meningeal disease to guide workup

STAGING SCALE

WHO drug-resistance categories

Stages as susceptible, multidrug-resistant, pre-extensively resistant and extensively resistant to guide regimen

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Prognosis

SHORT-TERM OUTCOME

Short term course follows site, resistance and HIV status. Drug-susceptible pulmonary disease often improves within weeks of therapy. Miliary and meningeal disease carry high early death risk. Delayed diagnosis with drug resistance worsens early outcome. Prompt combination therapy with isolation improves survival.

LONG-TERM PROGNOSIS

Most drug-susceptible cases cure with full course completion. Lung scarring with bronchiectasis (damaged airways) and airflow block can persist. Relapse follows incomplete treatment or resistance. HIV coinfection needs joint antiretroviral planning for lasting control. Long term lung and spine rehab needs grow with damage.

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References & Coding

ICD-10 DIAGNOSTIC CODE

A15

LITERATURE CITATIONS & GUIDELINES

[1]WHO ICD-10 A15-A19 Tuberculosis

[2]WHO consolidated guidelines on tuberculosis

[3]NICE NG33 Tuberculosis

[4]Harrisons Principles of Internal Medicine mycobacterial diseases

MEDICAL DISCLAIMER — This content is intended for educational purposes and qualified healthcare professionals only. Always refer to current clinical diagnostic criteria, institutional protocols, and official guidelines. Medobo is not responsible for clinical decisions made based on this content.