Miliary tuberculosis

When the diffuse spread of tuberculosis bacteria in the body is accompanied by the appearance of many very small foci in the form of tubercles - tubercles or granulomas - nodules the size of a grain of millet (in Latin - milium), miliary tuberculosis is diagnosed).

Such tuberculous foci in this type of disease can be not only in the lungs, but also in other organs. [1]

Epidemiology

According to WHO data for 2018, almost 10 million people were diagnosed with tuberculosis, and about 1.6 million patients died from it. At the same time, according to experts, on a global scale, about a third of the population can have a latent infection (especially in developing countries). [2]

Miliary pulmonary tuberculosis accounts for 1-2% of all cases of tuberculosis of this localization. And its extrapulmonary forms account for at least 20% of the total tuberculosis statistics. [3]

Causes of the miliary tuberculosis

Tuberculosis is known to be caused by infection with the bacteria Mycobacterium tuberculosis. The same pathogenic microorganism of the actinomycetes genus, which enters the body by airborne droplets, also causes multiple small-focal or disseminated miliary tuberculosis.

This progressive disease can occur during the primary hematogenous or lymphogenous dissemination (spread) of mycobacteria throughout the body or affecting other organs if the existing tuberculosis is not treated.

See also -  Disseminated pulmonary tuberculosis .

Miliary tuberculosis is contagious or not? Regarding the contagiousness of this type of lesion with tubercle bacilli, there is an opinion that the degree of its contagiousness to others is lower, since it is spread by blood (or lymph) flow. 

Tuberculosis bacteria are carried from sick people, and tuberculosis is contagious when there are clinical symptoms that indicate the activity of the pathogen. But if the mycobacterium does not lead to the development of the disease, that is, the infection in a person is latent (asymptomatic), he cannot infect others.

At the same time, as clinical experience shows, the result of a tuberculin skin test - the  Mantoux test  - is often false-negative, and in ten cases out of a hundred, the latent form eventually becomes active (contagious). And when this happens, it is impossible to predict. [4]

Risk factors

Indisputable risk factors for the development of miliary tuberculosis are contact with patients and conditions leading to immunosuppression - a weakening of the body's immune defenses.

And immunity is weakened:

• with HIV and AIDS, miliary tuberculosis is observed in 10% of patients with AIDS (see - Tuberculosis in HIV infection );
• with poor nutrition and chronic alcoholism;
• in cancer patients, including after chemotherapy;
• with chronic renal failure and permanent dialysis;
• due to antibody deficiency syndrome (hypogammaglobulinemia);
• in cases of long-term use of immunosuppressive drugs and corticosteroids.

Also, the risk of transition from latent infection to active tuberculosis is increased in diabetes.

Pathogenesis

Tuberculosis is an insidious and complex disease, and despite the fact that the pathogenesis of M. Tuberculosis is well known to phthisiatricians, the exact mechanism of damage in its miliary forms has not been fully elucidated.

In individuals infected with initially ingested mycobacteria, the upper or posterior segments of the lung lobes are usually affected, and activation of alveolar macrophages leads to phagocytosis of the bacilli. That is, immunity limits their further reproduction, and usually there are no clinical manifestations with such an infection.

But even with a latent form, Gon's foci (primary tuberculosis complexes with encapsulated inactive bacteria) can also contain bacilli that have retained their viability and are at rest. And if immunity weakens, endogenous reactivation of M. Tuberculosis occurs: they begin to multiply in macrophages, spreading to nearby cells and other organs by the hematogenous route.

The foci of miliary tuberculosis have the form of homogeneous micronodules (1-3 mm in diameter) diffusely scattered over the lungs of a dense consistency. [5]

At the same time, destructive changes in the lungs in miliary tuberculosis are manifested in the form of tissue infiltration with these nodules, which can unite, forming larger foci of alteration and causing fibrosis of the lung tissues.

Symptoms of the miliary tuberculosis

The first signs of miliary tuberculosis are manifested by a deterioration in the general condition and weakness.

The combination of symptoms, as well as signs of extrapulmonary localization of lesions, depend on the form of the disease.

Clinical forms of miliary tuberculosis include, first of all, miliary pulmonary tuberculosis, which is detected in 1-7% of patients with all forms of tuberculosis. With it, other typical  symptoms of tuberculosis are observed , in particular, nocturnal hyperhidrosis (excessive sweating); loss of appetite and weight loss; cough (dry or with mucus sputum) and progressive shortness of breath.

Most often, the manifestations of the disease are subacute or chronic; rarely occurs acute miliary tuberculosis.

In the acute course of generalized tuberculosis, chills and high hepatic fever (with temperature jumps) are noted; cardiopalmus; labored breathing; cyanosis of the skin; nausea and vomiting (indicative of intoxication), impaired consciousness. Such a condition - due to some similarity with the symptoms of typhoid fever - can be defined as a typhoid form or typhoid miliary tuberculosis, which most often develops during a primary infection.

With an extrapulmonary form of the disease, the infection can affect several organs at once. And then patients are diagnosed with miliary tuberculosis of multiple localization, which manifests itself with a variety of, often non-specific symptoms and leads to dysfunction of the affected organ or a certain organ system.

So, miliary tuberculosis of the liver can be asymptomatic, or it can be accompanied by fever and hyperhidrosis and lead to organ hypertrophy - hepatomegaly.

Also read:

• Tuberculosis of the intestine
• Tuberculosis of the pancreas
• Tuberculosis of the kidneys
• Tuberculosis of the meninges (tuberculous meningitis)

One of the rarely diagnosed forms of  tuberculosis of extrapulmonary localization  is miliary tuberculosis of the skin, which in adults is considered a secondary form of the disease (the result of hematogenous spread of infection from the primary focus), and in childhood and adolescence - the primary form, with infection of the skin by contact. The most common affected areas are the face, neck, extensor surfaces of the limbs and torso. Against the background of constitutional symptoms of tuberculosis, many small red nodules appear on the skin that do not cause itching or pain, but very quickly turn into ulcers, so the diagnosis can be determined as miliary-ulcerative tuberculosis of the skin and subcutaneous tissues. [6]

Complications and consequences

Oxygen deficiency (respiratory distress syndrome) associated with a pathological change in the alveolar walls and a violation of the diffusion of oxygen into the blood; pleural empyema with fibrothorax; the formation of a bronchopleural fistula is a complication of miliary pulmonary tuberculosis.

Miliary tuberculosis of the liver can be complicated by an increase in the level of bilirubin in the blood and the development of jaundice, as well as fatty hepatosis and amyloid degeneration. Bowel obstruction is the most common complication of miliary intestinal tuberculosis.

Meningeal miliary tuberculosis (which is at increased risk in children) can lead to increased intracranial pressure, hydrocephalus, and cranial nerve palsies. And the consequence of the generalized form of the disease is multiple organ failure. [7]

Diagnostics of the miliary tuberculosis

Early diagnosis contributes to the effective treatment of miliary tuberculosis and the reduction of further transmission of infection, but specialists conducting  examinations of patients with tuberculosis recognize the presence of certain difficulties - due to the many varieties of the disease and the non-specific clinical manifestations of many forms.

Standard tests are required: isolation of M tuberculosis from sputum and bronchial lavage, PCR analysis of the tubercle bacillus DNA, analysis of the level of adenosine deaminase in the blood, ESR. Histology of tissue biopsy samples is also performed. [8]

More:

• Laboratory diagnosis of tuberculosis
• Tuberculosis: detection of Mycobacterium tuberculosis
• Methods for detecting tuberculosis

How instrumental diagnostics is carried out, the main method of which is radiography, and ultrasound, high-resolution CT and MRI can be used to clarify the diagnosis, for details in the publication -  Instrumental Diagnosis of Tuberculosis .

Miliary tuberculosis on a chest x-ray is visualized by small-focal dissemination of both lungs - an accumulation of many clearly defined scattered fibronodular opacities. Some patients may have a unilateral pleural effusion with thickening of the visceral and parietal pleura.

Differential diagnosis

Differential diagnosis is important: miliary pulmonary tuberculosis must be distinguished from cryptococcosis and sarcoidosis of the lungs, from malignant pleural mesothelioma; miliary tuberculosis of the brain - from meningococcal or staphylococcal meningitis; cutaneous miliary tuberculosis requires especially careful differentiation from dermatological diseases, with syphilis rashes (tubercular syphilides), etc. 

More information in the materials:

• Diagnosis of tuberculosis of extrapulmonary localization
• Diagnosis of the tubercle of the meninges

Treatment of the miliary tuberculosis

The main  treatment for tuberculosis  of any form is etiotropic, lasting 6-12 months; the main drugs are anti-tuberculosis antibacterial drugs:  Isoniazid , Rifampicin,  Macrozid 500  (Pyrazinamide, Pyrazidine), Sodium para-aminosalicylate, etc.

Read more about their side effects, contraindications, methods of use and dosage in the publication -  Pills for tuberculosis .

With abscess formation of lesions and tissue necrosis, surgical treatment is performed.

Prevention

The main preventive measure is BCG vaccination or  vaccination against tuberculosis .

Also read:

• Sanitary and social prevention of tuberculosis
• Chemoprophylaxis of tuberculosis

In cases of detected latent infection, preventive  prophylactic treatment of tuberculosis is possible .

Forecast

Miliary tuberculosis is a life-threatening disease; deaths from miliary tuberculosis are observed in almost 27% of cases among adult patients, and in children - more than 15% of cases. [9], [10]

A favorable prognosis can only be achieved with the earliest possible detection of infection and effective antibiotic therapy.