Tuberculosis

Infectious disease caused by Mycobacterium tuberculosis (MT) complex

Pathogenesis

Too long lol. Read pdf once or just go through variants

Types of Tuberculosis

By time

• Primary

  • Naive host: no previous immunity

  • Exogenous source

  • 5% of infected persons develop clinical illness

  • More frequent in children and in immunocompromised

• Secondary

  • in sensitised host

  • Enhanced by Immunosuppression, Reinfection and Time

By localisation

• Pulmonary

• Extrapulmonary

Risk of infection

Exogenous

• Contact with patient / MT+

• Length of contact

• Intimacy of contact

• The amount of MT discharge

Endogenous

• Immune system status: risk ↑

  • Diabetes mellitus

  • Status post transplantation

• Cellular immunity status: risk ↑

  • HIV

  • Inborn immunodefficiencies affecting the cellular immunity 

• General status

  • Malnutrition

  • Malabsorbtion etc

Primary Tuberculosis

• Directly after infection

• Mainly in children

• Affects mainly middle and lower lobe

Primary complex s. Ghon complex

Ways of progression:

• Tuberculous pleuritis

• Progressive primary lung tuberculosis

Risk factors of progression:

• Small children

• HIV

• Malnutrition

Progressive primary pulmonary tuberculosis

• Resemble acute bacterial pneumonia

• In middle and lower lobes

• Hilar lymphadenopathy

• Pleurisy

• Occasionally – caverns (less frequent than in secondary tbc)

• Dissemination:

  • Meningitis

  • Miliary tbc

Secondary Pulmonary Tuberculosis

• Sensibilised host

• Source of infection: exogenous or endogenous

• Apical: [O]

• DTH is present:

  • Lymphadenopathy is not marked

  • Tissue destruction is characteristic (due to DTH): cavernous tbc

• Mechanism: reactivation or reinfection (30%)

• Predilection area:

  • Pulmonary apex

  • The posterior segments of upper lobes

  • The upper segments of lower lobes

• Main processes

  • Infiltration

  • Cavitation

  • Fibrosis

  • Systemic manifestations

  
  

Local Symptoms and Systemic manifestations

Pathogenesis of local symptoms

• Cough

• Haemoptysis (coughing up blood)

  • 20 – 30 – 50%

  • Can be small

  • Can be massive

    • Destruction of large blood vessel

    • Rasmusen aneurysm

    • Aspergilloma

Systemic manifestations of tuberculosis

• Systemic manifestations of inflammation

• Mf: TNF, IL-1

• Components / clinical manifestations

  • Fever, mainly low grade

  • Night sweats

  • Weakness

  • Anorexia

  • Weight loss

Miliary lung tuberculosis

Milia: multiple small foci of necrotising granulomatous inflammation, affecting all lobes of both lungs

• Lymphogeneous retrograde spread

• Blood-born spread via pulmonary circulation

• Local symptoms and radiological findings are scant

Endobronchial tuberculosis

• Usually associated with bronchogeneous dissemination

Extrapulmonary Tuberculosis

Locations in the order of decreasing frequency:

• Lymph nodes (LN)

• Pleura

• Urogenital system

• Bones

• CNS

• GI

• Peritoneum

• Pericardium

LN tuberculosis

Predilection sites: Neck LN, Supraclavicular LN

Course:

• Necrotising granulomatous inflammation

• LN increase in size but are not painful

• Soft

• Fistula formation

Typical groups of patients: Children; HIV

Pleural pathology in tuberculosis

• Exudative pleuritis

  • Hypersensitivity

  • Direct spread from subpleural focus

  • Hydrothorax

  • Clear yellowish or reddish exudate

  • Cells: Ly / Neu

  • Reacts on drug treatment

• Tuberculous empyema

  • Rupture of a cavern towards pleural space

  • Less frequent

  • Hydropneumothorax

  • Thick content

  • Ly

  • Drug treatment / Surgery

  • Can result in severe fibrosis / restrictive pulmonary lesion. Surgical decortication can be necessary

Tuberculosis of upper airways

• Larynx, pharynx, epiglottis

• Spread from lungs due to expectoration of infected necrotic masses

Renal tuberculosis

Manifestations:

• Local

  • Can be absent

  • Frequent urination, dysuria, nicturia, haematuria

  • Hydronephrosis due to ureteral stricture

Genital Tuberculosis

In female

• Salpingitis, endometritis

• Pain, infertility, bleeding

In males

• Epididymis

• Fistula

• Possible orchitis and prostatitis

Bone Tuberculosis

• Spread: haematogeneous

• Predilection: weight-bearing bones

  • 40% spine

    • Upper Th in children

    • Lower Th / L in adults

  • 13% hip

  • 10% knee

CNS tuberculosis

Types:

• Tuberculous meningitis

  • Spread: haematogeneous

  • Slow progress (1 – 2 weeks)

  • Basal predominance: cranial nerves

  • Vascular damage leading to ischemia

  • Coma, hydrocephalus, intracranial hypertension

• Tuberculoma (very rare). Manifests by focal neurologic and radiologic symptomatics

Gastrointestinal (GI) Tuberculosis

• Routes:

  • Haematogeneous

  • Peroral by infected sputum

  • Peroral by infected milk

• Predilection: terminal ileum and caecum

Symptoms:

Local:

• Obstruction, ulcers and fistulae

• Rectal fistulae

• Resemble Crohns disease

Systemic manifestations

Tuberculosis peritonitis

Spread:

• Haematogeneous,

• Direct

  • GI, fallopian tubes

  • LN

Symptoms:

• Pain: inflammation, adhesions

• Exudation

• Fever and other systemic manifestations

Tuberculosis pericarditis

• Spread:

  • Haematogeneous

  • Direct from mediastinal or hilar LN

• Death rate 40%

• Course

  • Subacute or acute

  • Heart tamponade

  • Constrictive pericarditis

Tuberculosis myocarditis

• VERY rare

• Spread:

  • Direct from tuberculous pericarditis

  • Retrograde lymphogeneous spread from mediastinal LN

• Deadly in most cases

Tuberculosis of other organs

• Any organ can be affected, e.g., thyroid gland and others

• Suprarenal TBC with suprarenal insufficiency: Addison’s disease

Tuberculosis diagnosis

• Clinical picture

• Epidemiology

• Radiology

• Identification of MT:

  • In smear;

  • By culture

• Histology

Sepsis

explained before in other notes