Infectious Disease · Mycobacterial Infections
The facts most likely to be tested
Primary pulmonary tuberculosis typically presents with a Ghon focus in the lower lobes and ipsilateral hilar lymphadenopathy, collectively known as the Ghon complex.
Reactivation tuberculosis classically manifests as cavitary lesions in the apical/upper lobes due to the high oxygen tension in these areas.
The gold standard for diagnosis is sputum culture on Lowenstein-Jensen agar, though NAAT (nucleic acid amplification test) is the preferred initial rapid diagnostic tool.
Extrapulmonary tuberculosis most commonly affects the spine, known as Pott disease, which presents with vertebral body destruction and psoas abscess.
The standard initial treatment regimen for active tuberculosis is the RIPE therapy consisting of Rifampin, Isoniazid, Pyrazinamide, and Ethambutol for two months, followed by four months of Rifampin and Isoniazid.
Isoniazid therapy is associated with peripheral neuropathy and hepatotoxicity, necessitating concurrent administration of pyridoxine (Vitamin B6).
Ethambutol is uniquely associated with optic neuritis, which manifests as red-green color blindness and decreased visual acuity.
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A 34-year-old immigrant from Southeast Asia presents with a 3-month history of chronic cough, night sweats, and a 10-lb unintentional weight loss. Physical examination reveals dullness to percussion and bronchial breath sounds at the right lung apex. A chest X-ray demonstrates a cavitary lesion in the right upper lobe. Sputum acid-fast bacilli smear is positive.
What is the most appropriate initial four-drug regimen for this patient?
Rifampin, Isoniazid, Pyrazinamide, and Ethambutol
The patient's presentation of apical cavitation and constitutional symptoms is classic for reactivation tuberculosis, which requires the standard RIPE induction therapy.
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Etiology / Epidemiology
Caused by Mycobacterium tuberculosis; high risk in immigrants, HIV+, and crowded living conditions.
Clinical Manifestations
Chronic cough, night sweats, and hemoptysis; Ghon complex on imaging.
Diagnosis
Sputum acid-fast bacilli (AFB) smear/culture is gold standard; IGRA or TST for latent screening.
Treatment
RIPE therapy (Rifampin, Isoniazid, Pyrazinamide, Ethambutol) for 2 months, then RI for 4 months.
Prognosis
High cure rate with adherence; multidrug-resistant TB (MDR-TB) requires prolonged, complex regimens.
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Epidemiology & Etiology
Transmitted via aerosolized droplets. Primary risk factors include HIV infection, recent travel to endemic areas, and homelessness/incarceration. Reactivation occurs in the immunocompromised or elderly.
Pertinent Anatomy
Primary infection typically involves the mid/lower lung zones. Reactivation TB classically localizes to the apices due to higher oxygen tension.
Pathophysiology
Inhaled bacilli are phagocytosed by alveolar macrophages, forming a granuloma. Caseous necrosis leads to cavitation and potential hematogenous spread to extrapulmonary sites like the spine (Pott disease).
Clinical Manifestations
Patients present with fever, weight loss, and night sweats. Hemoptysis is a late, concerning sign. Physical exam may reveal amphoric breath sounds or post-tussive apical rales.
Diagnosis
Sputum culture is the gold standard. TST (PPD) is positive at ≥5mm in HIV/immunosuppressed, ≥10mm in high-risk groups, and ≥15mm in low-risk individuals.
Treatment
Initiate RIPE therapy. Isoniazid requires pyridoxine (B6) to prevent peripheral neuropathy. Ethambutol requires baseline eye exams due to optic neuritis. Rifampin causes orange-colored body fluids.
Prognosis
Treatment success depends on directly observed therapy (DOT). Hepatotoxicity is a major monitoring concern for R, I, and P. Failure to adhere leads to MDR-TB.
Differential Diagnosis
Lung Cancer: weight loss without fever/night sweats
Histoplasmosis: exposure to bird/bat droppings
Sarcoidosis: bilateral hilar adenopathy without systemic infection
Pneumonia: acute onset with lobar consolidation
Lung Abscess: foul-smelling sputum and aspiration risk