Alveolar microlithiasis of the lungs: causes, symptoms, diagnosis, treatment

Alveolar microlithiasis of the lungs is a disease characterized by the deposition of substances in the alveoli consisting of mineral compounds and proteins. The disease is rare, occurs at any age, but mainly at the age of 20-40 years. Women are more often affected.

Cause, pathogenesis, pathomorphology of alveolar microlithiasis of the lungs

The cause and pathogenesis are unknown. In many patients, hereditary factors and the influence of occupational hazards are important.

The essence of the disease lies in the hyperproduction and accumulation of protein in the alveoli, in which microcrystals of calcium carbonate and phosphate are deposited, which disrupts the processes of ventilation and perfusion, leading to the development of interstitial fibrosis and respiratory failure.

The characteristic pathomorphological signs of the disease are:

• increased density of lung tissue, especially in the lower lobes;
• detection of microstones in the alveoli and bronchioles with a diameter of 1-3 mm, containing calcium carbonate and phosphate, as well as trace elements sodium, potassium, copper, zinc, magnesium; microliths have a concentric complex structure;
• development of interstitial fibrosis as the disease progresses;
• detection of macrophages in the area of microliths.

Symptoms of alveolar microlithiasis of the lungs

Alveolar microlithiasis goes unnoticed for a long time. However, as it progresses, complaints of shortness of breath, rapid fatigue, general weakness, palpitations during physical exertion, and chest pain appear. A cough may appear due to the development of chronic bronchitis.

In the stage of the developed clinical picture, cyanosis of the visible mucous membranes, inspiratory dyspnea, thickening of the terminal phalanges in the form of "drumsticks" and changes in the nails in the form of "watch glasses" occur. With the development of decompensated pulmonary heart disease, swelling of the legs and pain in the right hypochondrium due to an enlarged liver appear.

Physical examination of the lungs does not reveal significant changes. Some patients may have a box-like shade of percussion sound (due to the development of emphysema), crepitation or fine bubbling rales may be heard in the lower parts of the lungs.

1 When auscultating the heart, an accent of the second tone on the pulmonary artery is determined (with the development of pulmonary hypertension), the formation of mitral stenosis is possible with the appearance of corresponding sound symptoms (flapping first tone, click of the mitral valve opening, "quail" rhythm, presystolic and protodiastolic murmurs). The development of mitral stenosis is due to calcification of the left atrioventricular orifice.

Laboratory data

1. General blood analysis - no significant characteristic changes. With the development of severe respiratory failure, symptomatic erythrocytosis appears, with the addition of purulent bronchitis, ESR increases, leukocytosis appears.
2. Analysis of sputum and bronchial lavage fluid - microliths may be detected, but this sign is not given much diagnostic value, since it can be present in chronic obstructive bronchitis and pulmonary tuberculosis.

At the same time, there is an opinion that the concentric structure of the detected microliths is characteristic of alveolar microlithiasis.

3. Biochemical blood test - there may be hypercalcemia, a slight increase in phosphate levels, but these changes are irregular and do not have much diagnostic value.
4. Immunological studies - no significant changes.

Instrumental research

1. X-ray examination of the lungs. A characteristic sign of alveolar microlithiasis in the early stage is the detection of symmetrical multiple small-focal shadows of high intensity predominantly in the middle and lower parts of both lungs. The X-ray picture resembles scattered sand - the "sandstorm" symptom. This symptom is considered pathognomonic for alveolar microlithiasis.

As the disease progresses, against the background of persistent above-mentioned symptoms, pronounced signs of interstitial changes (perivascular, peribronchial, interlobar pneumosclerosis) appear, and compacted and calcified bronchial walls are revealed. Along with the intensification of interstitial changes, the number of focal rashes increases, and the transparency of the lung tissue decreases. These changes are most pronounced in the lower and middle sections; in the upper sections, large air emphysematous bullae are sometimes determined.

In the advanced stage of the disease, small focal shadows merge into massive darkening areas, they can occupy 1/2-2/3 of the pulmonary lobe and also capture the upper parts of the lungs. Conglomerates of focal darkening can be so intense and extensive that they make it difficult to differentiate the shadows of the heart and mediastinum.

Quite often, calcification along the cardiac contours, as well as subpleural accumulation of calcium, can be seen on radiographs.

2. Computed tomography of the lungs reveals diffuse calcification of the lung tissue.
3. Perfusion lung scintigraphy with 99mTc- reveals intense diffuse accumulation of the isotope, confirming calcification of lung tissue.
4. A study of the ventilation function of the lungs reveals the development of a restrictive type of respiratory failure (decreased vital capacity).
5. Blood gas analysis - as the disease progresses and respiratory failure develops, the partial oxygen tension in arterial blood decreases.
6. ECG - with the development of pulmonary hypertension, signs of myocardial hypertrophy of the right atrium and right ventricle appear.
7. Lung tissue biopsy examination is used to verify the diagnosis. In the biopsy material, microliths in the alveoli are determined using light and electron microscopy, and an excessive amount of glycogen granules is detected in the epithelial cells of the bronchioles.

Examination program for alveolar microlithiasis of the lungs

1. General blood and urine tests.
2. Biochemical blood test: determination of total protein, protein fractions, aminotransferases, calcium, phosphorus, alkaline phosphatase.
3. Analysis of sputum and bronchial washings - detection of microliths with a concentric structure.
4. X-ray examination of the lungs, if possible - computed tomography of the lungs.
5. Spirometry.
6. ECG.
7. Lung biopsy (transbronchial, if it is not informative - open).

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