Acute miliary tuberculosis of the lungs, also known as acute hematogenous disseminated pulmonary tuberculosis, is a form of pulmonary tuberculosis caused by hematogenous dissemination of Mycobacterium tuberculosis. It is often a consequence of the progression of the primary complex and is predominantly observed during childhood, particularly in infants and young children. Factors such as young age, measles, pertussis, malnutrition, immune deficiency, and especially HIV infection increase susceptibility to this condition. Infants and children frequently develop complications such as tuberculous meningitis.
Pathology
Acute miliary tuberculosis typically develops within 3–6 months of the primary infection. Due to immature immune function in infants and young children, heightened sensitivity to Mycobacterium tuberculosis often results in mycobacteremia. When caseous necrosis of primary lesions or lymph nodes ruptures, a large number of bacteria enter the bloodstream, leading to acute systemic miliary tuberculosis. This process may involve the lungs, meninges, brain, liver, spleen, kidneys, heart, adrenal glands, intestines, peritoneum, and mesenteric lymph nodes. In these organs, Mycobacterium tuberculosis forms small nodular lesions within interstitial tissues.
In the lungs, these tuberculous nodules are more frequently distributed in the upper lobes compared to the lower lobes. The nodules appear as grayish-white translucent or pale-yellow opaque lesions, approximately 1–2 mm in size, resembling millet seeds or pinpoints.
Microscopic examination reveals that the nodules consist of epithelioid cells, lymphocytes, and Langerhans cells, with a central area of caseous necrosis characteristic of tuberculous granulomas.
Clinical Manifestations
The onset is often abrupt. Infants and young children typically experience sudden high fever (39–40°C), which may manifest as sustained fever or remittent fever. In some cases, the temperature may be less elevated, with a regular or irregular febrile pattern persisting for several weeks or months. Accompanying symptoms often include chills, night sweats, loss of appetite, coughing, pallor, rapid breathing, and cyanosis.
Fine moist rales may be audible in the lungs, which can lead to misdiagnosis as pneumonia. Over 50% of affected children exhibit signs of meningitis at disease onset, and some patients may show hepatosplenomegaly and superficial lymphadenopathy.
For infants younger than six months, acute miliary tuberculosis is characterized by rapid onset with severe but atypical symptoms. Multiple organ involvement is common, particularly with frequent complications such as tuberculous meningitis. The disease progresses rapidly, with a high case fatality rate.
Choroidal tubercles are detectable on fundoscopic examination in patients with systemic miliary tuberculosis. These tubercles are typically distributed around branches of the central retinal artery.
Diagnosis and Differential Diagnosis
Diagnosis is primarily based on a history of tuberculosis exposure, clinical symptoms, hepatosplenomegaly, and a positive tuberculin skin test. For suspected cases, pathogen detection and chest imaging are essential. Chest X-rays often play a decisive role, although miliary shadows may be too small to detect in the early stages. It typically requires at least 2–3 weeks after symptom onset for X-rays to reveal uniformly distributed, evenly sized miliary opacities across both lung fields.
Pulmonary CT scans can display miliary lesions with uniform size, density, and distribution, some of which may show partial consolidation. Differential diagnosis includes pneumonia, typhoid fever, sepsis, Langerhans cell histiocytosis, pulmonary hemosiderosis, and idiopathic interstitial lung diseases.
Treatment
Antituberculosis Drugs
The current standard of care divides the full course of treatment into two stages: an intensive phase and a maintenance phase, aiming to enhance treatment efficacy. The intensive phase uses a potent combination of four bactericidal drugs, such as isoniazid (INH), rifampin (RFP), pyrazinamide (PZA), and streptomycin (SM). Earlier initiation of treatment yields better bacterial eradication, reduces the likelihood of resistance, and remains effective even in cases of primary drug resistance.
Glucocorticoids
In patients with severe symptoms or respiratory distress, prednisone at 1–2 mg/(kg·d) may be co-administered alongside a full-dose antituberculosis regimen. The treatment duration typically lasts 1–2 months.
Prognosis
Although acute miliary tuberculosis is a severe and rapidly progressing condition, early diagnosis and thorough treatment can result in a full recovery. Delays in diagnosis and treatment, however, may lead to fatal outcomes.