From the Guidelines
Miliary tuberculosis is a severe form of tuberculosis characterized by widespread dissemination of Mycobacterium tuberculosis throughout the body, resulting from the bacteria overcoming local immune defenses and entering the bloodstream or lymphatic system, leading to hematogenous spread and the formation of numerous small granulomatous lesions in multiple organs. The pathophysiology of miliary tuberculosis begins with primary infection, typically in the lungs, where M. tuberculosis bacilli are inhaled and establish infection in the alveoli [no direct evidence from 1]. Key factors that contribute to the development of miliary TB include:
- Immunosuppression, particularly HIV infection
- Extremes of age
- Malnutrition
- Diabetes These factors can lead to a failure of the host's cell-mediated immunity to contain the infection, allowing the bacteria to disseminate widely [no direct evidence from 1]. The widespread seeding of M. tuberculosis occurs when either a tuberculous focus directly erodes into a blood vessel, allowing massive bacterial release into circulation, or when the host's cell-mediated immunity fails to contain the infection [no direct evidence from 1]. The resulting systemic inflammatory response to these widespread granulomas leads to the clinical manifestations of fever, weight loss, and organ-specific symptoms depending on the sites involved [no direct evidence from 1]. Without prompt treatment with standard anti-tuberculosis therapy, miliary TB has a high mortality rate due to progressive multi-organ dysfunction [no direct evidence from 1]. However, the provided evidence 1 discusses the treatment of drug-susceptible tuberculosis and the management of relapses, which may be relevant in the context of miliary TB, but does not directly address the pathophysiology of the disease.
From the Research
Pathophysiology of Miliary Tuberculosis
The pathophysiology of miliary tuberculosis is characterized by the hematogenous dissemination of Mycobacterium tuberculosis bacilli, leading to a potentially lethal form of tuberculosis 2. This dissemination results in the impairment of cell-mediated immunity, which underlies the development of the disease 2.
Key Features
- Miliary tuberculosis is a serious and uncommon form of tuberculosis, accounting for 13% of proportional morbidity in some studies 3.
- The disease is often associated with non-specific clinical manifestations, and typical chest radiographic findings may not be seen until late in the course of the disease 2.
- Atypical presentations, such as cryptic miliary tuberculosis and acute respiratory distress syndrome, can delay diagnosis 2.
- Laboratory abnormalities, including pulmonary function and gas exchange impairment, have been described, with prognostic and therapeutic implications 2.
Diagnosis and Treatment
- Diagnosis is often confirmed through isolation of M. tuberculosis from sputum, body fluids, or biopsy specimens, as well as molecular methods such as PCR and histopathological examination of tissue biopsy specimens 2.
- Treatment with first-line antituberculosis drugs is generally effective, but evidence regarding optimum duration of treatment is lacking, and the role of adjunctive corticosteroid treatment is unclear 2.
- Multidrug-resistant tuberculosis, defined by resistance to isoniazid and rifampin, is a significant concern, with rising global incidence and associated morbidity and mortality 4, 5, 6.