Definition
A.An infectious disease characterized by the growth of tubercles (nodules).
B.One of the oldest diseases known to affect humans, most frequently affecting the lungs, although up to 1one third of cases occur outside of the pulmonary system.
Incidence
A.One of the top 10 leading causes of death worldwide, tuberculosis (TB) ranks higher than malaria and HIV. TB is a leading killer of HIV-positive individuals; in 2015, 35% of deaths in those with HIV were due to TB.
Pathogenesis
A.General information.
1.Cause: Bacterium Mycobacterium tuberculosis.
2.Dispersion: Spread by M. tuberculosis bacilli-infected airborne droplets, through coughing, sneezing, speaking, and singing.
B.Primary tuberculosis.
1.Active disease that develops in previously unexposed patients.
2.Almost always starts in the alveoli of the lungs.
C.Latent tuberculosis infection (LTBI).
1.Exposure to M. tuberculosis without development of active disease. M. tuberculosis can stay dormant in the exposed host for decades.
2.Noncontagious: Can turn into active TB disease if left untreated. About 5% to 10% of persons who do not receive treatment for LTBI infection develop active TB disease at some time in their lives.
D.Extra-pulmonary TB: Can affect any organ/system in the body. It may occur in 10% to 40% of infected individuals; the most common sites are:
1.Lymph nodes (tuberculous lymphadenitis).
2.Pleura.
3.Upper airways.
4.Genitourinary tract.
5.Skeletal.
6.Central nervous system (CNS/meninges).
7.Gastrointestinal (GI).
8.Pericardium (tuberculous pericarditis).
9.Miliary/disseminated TB.
E.Drug-resistant TB.
1.Certain strains of M. tuberculosis bacillus are resistant to the drugs normally used to treat the disease.
F.Previous exposure.
1.Individuals with positive tuberculosis skin test (TST) are less susceptible to a new M. tuberculosis infection than individuals with a negative TST.
2.Previous latent or active TB infections may not confer protective immunity.
Predisposing Factors
A.Decreased immune status of the host.
1.HIV.
2.Posttransplant patient on immunosuppressive therapy.
3.Cancer patient on chemotherapy.
4.Intravenous (IV) drug abuse history.
B.Malnutrition.
C.History of smoking tobacco/alcohol abuse/intravenous drug use.
D.Chronic renal failure/hemodialysis.
E.Recent infection with pulmonary fibrotic changes.
F.Post jejunoileal bypass/gastrectomy.
G.Elderly individuals with comorbidities and inconsistent immune response.
H.Crowded living conditions.
I.Healthcare workers.
J.Migration from/travel to a country with a high volume of TB cases.
K.Extremes in age: Very young and very old.
Subjective Data
A.Common complaints/symptoms.
1.Early active TB disease: May be asymptomatic.
2.Fever.
3.Unexplained productive cough for more than 2 weeks (cough is seldom a presenting symptom in HIV patients).
4.Hemoptysis: Sign of advanced infection.
5.Loss of appetite/weight loss.
6.Malaise/fatigue.
7.Night sweats.
B.Common/typical scenario.
1.Generally, exposure from infected droplets by coughing, sneezing, speaking, or singing.
2.Slow symptom progression (over months).
a.Worsening productive cough.
b.Low grade fever.
c.Night sweats.
d.Fatigue.
e.Weight loss.
3.Hemoptysis and/or pleuritic pain, which indicates severe disease.
4.Detailed medical history: TB.
a.Presence of TB symptoms: If so, for how long?.
b.Known exposure to individuals with infectious TB disease: When?
c.Residence in high-risk congregate settings, such as prisons, long-term care facilities, and homeless shelters.
d.Past medical diagnosis of latent TB or previous known TB disease and previous treatment.
e.Comorbid diseases, which may increase risk of TB progression, including:
i.HIV.
ii.Diabetes mellitus.
C.Family and social history.
1.TB: An infectious disease with no known genetic predisposition.
2.Social stigma/poor knowledge about TB: Possibly difficult to obtain accurate history.
3.Recent travel to areas of known high prevalence of TB, such as Central/South America, Russia, Africa, Eastern Europe, and Asia.
D.Review of systems.
1.General: Fever, night sweats, weight loss, and fatigue.
2.Vision: Icteric sclera.
3.Head/neck: Headache, neck pain, swelling/soreness of lump in throat, and hoarseness.
4.Respiratory: Shortness of breath, cough, coughing up blood, and pleuritic chest pain.
5.Neurological: Change in level of consciousness/mental status, generalized weakness.
6.Endocrine: Fatigue, polyuria, polydipsia, polyphagia, and weight loss.
7.Musculoskeletal: Bone/joint pain.
E.Mental health: Alcohol/drug abuse.
F.Skin/hair: Presence/change in lesions/lumps.
Physical Examination
A.General.
1.Many individuals with primary TB are asymptomatic (about 90% early onset).
2.Once symptoms present, constitutional symptoms include weakness, fatigue, fever, chills, night sweats, loss of appetite, and jaundice.
B.Head, ear, eyes, nose, throat (HEENT; TB of eyes, mouth, nose).
1.Headache (meningeal TB).
2.Nonhealing oral ulcers/dysphagia (GI tract TB).
3.Icteric sclera.
4.Bleeding gums.
5.Epistaxis.
6.Hoarseness.
C.Neck (lymphatic TB/pericardial TB).
1.Lymphadenitis.
2.Jugular venous distention (late sign of pericardial tamponade).
D.Neurological (meningeal TB).
1.Altered mental status, confusion.
2.Coma.
E.Respiratory (pulmonary TB).
1.Decreased, absent, coarse breath sounds.
2.Dyspnea, tachypnea, sputum production, cough, and hemoptysis (pulmonary TB).
F.Skin.
1.Jaundice.
2.Pruritic rash, which may lead to ulcers and abscesses.
3.Various stages of bruising.
Diagnostic Tests
A.Mantoux TST.
1.Small wheel
of tuberculin fluid is injected under the skin.
2.Positive skin test means the individual has been infected with the TB bacteria.
a.Greater than 5 mm induration is positive for:
i.HIV.
ii.Recent exposure.
iii.Fibrotic changes on chest x-ray.
iv.Organ transplant.
v.Patients on immunosuppression medications.
b.Greater than 10 mm induration is positive for:
i.IV drug users.
ii.Recent immigrants from high-risk areas.
iii.Residents/employees of high-risk congregate settings.
iv.Microbial lab personnel.
c.Greater than 15 mm or more induration is positive for:
i.Any individual, even with no risk factors.
3.A negative skin test does not exclude a diagnosis of latent TB or active TB disease.
4.Targeted TST programs are recommended for use only in high-risk groups.
B.Approved TB blood tests in the United States: Interferon gamma release assays (IGRAs).
1.QuantiFERON-TB test.
2.T-SPOT TB test.
C.Acid-fast bacilli (AFB) testing: Smear and culture.
1.Culture remains the gold standard for diagnosis and identifying drug susceptibility and genotyping.
2.Sputum specimens should be obtained from all individuals suspected of having active TB disease, both pulmonary and extra-pulmonary, with or without respiratory symptoms.
a.At least three sputum specimens should be collected at consecutive intervals, 8 to 12 hours apart.
b.At least one of the specimens should be an early morning specimen.
D.Imaging: Cannot be used alone to distinguish active TB from latent TB.
1.Chest x-ray with a posterior–anterior view is the standard approach.
a.Although abnormalities may be seen anywhere on a chest x-ray, TB lesions are most often noted in the apical and posterior sections of the upper lobes or superior sections of the lower lobes.
b.Chest x-rays can be used to rule out active pulmonary TB in an asymptomatic, immunocompetent individual with a positive TST or IGRA.
2.Chest CT is recommended if any suspicions for TB are noted after chest x-ray.
Differential Diagnosis
A.Pulmonary TB.
1.Nontuberculous mycobacterial (NTM) infection.
2.Fungal infections.