Alveolar microlithiasis is a rare lung disease characterized by the formation of protein-mineral complexes in the lumen of the alveoli. Clinically manifested by increasing shortness of breath, general weakness, cough, heaviness and pressure in the chest. As the pathology progresses, symptoms of respiratory and heart failure are added. Diagnostic measures include radiation methods of examination of the chest organs, laboratory tests, ECG, spirometry, lung biopsy. There is no etiotropic treatment for this pathology. Symptomatic therapy is prescribed.General information
Alveolar (pulmonary) microlithiasis is a disease of accumulation. It occurs as a result of the deposition of protein in the alveoli, which is subsequently impregnated with metal salts, mainly calcium compounds, to a lesser extent magnesium. The disease is rare. To date, only about 400 cases have been described in the specialized literature. Men and women from different age groups are equally often ill. Often the pathology is congenital in nature, sometimes combined with other malformations. Approximately 25% of all cases of the disease are diagnosed in childhood. About 50% of patients are blood relatives.
The causes of pulmonary microlithiasis have not been fully studied. A genetic etiology is assumed with the inheritance of the disease according to an autosomal recessive type. This theory is confirmed by family cases of the disease, as well as the identification of this pathology in children whose parents were close relatives. An additional prerequisite for the development and progression of microlithiasis is prolonged inhalation of dust containing compounds of calcium, magnesium and some other metals. Such dust enters the body during the production and use of cement, agricultural fertilizers, steel recycling, and the use of snuff.
Presumably, the genetic defect leads to a violation of metabolic processes and a decrease in the synthesis of alveolar fluid, hyperproduction and accumulation of protein in the pulmonary alveoli and bronchioles. This protein is impregnated with calcium salts and forms a microlith (a 0.3-2mm concretion). The alveolar lumen is half or more filled with micro-increment. The process gradually affects the entire pulmonary parenchyma. The lungs become stony-dense and heavy. Alveolar blood flow and gas exchange are disrupted. Respiratory failure develops.
Pathomorphological examination reveals an increase in the density of lung tissue in the basal and middle sections. Sometimes the weight of the lungs can reach 4 kilograms. Microliths of a complex concentric structure are found in the lumen of the alveoli and bronchioles. Calcium carbonates and phosphates, as well as magnesium, zinc, sodium, copper and other trace elements are detected in the composition of the smallest concretions. Signs of fibrosis are detected in interstitial lung tissue.
Alveolar microlithiasis is characterized by a chronic, steadily progressive course. The symptoms of the disease appear and become heavier as microliths accumulate in the pulmonary alveoli and the compensatory capabilities of the patient’s body are depleted. The pathological process proceeds in stages. There are the following stages of the disease:
- Stage I. The formation of microliths occurs. At this stage, microlithiasis is asymptomatic. Radiological signs can be detected during preventive X-ray examination of the lungs.
- Stage II. Respiratory disorders appear, partially compensated by the reserves of the body.
- Stage III. A pulmonary heart is formed, pulmonary-cardiac decompensation occurs.
For a long period of time, pulmonary microlithiasis proceeds covertly. At first, the signs of the disease are weakly expressed. One of the first clinical manifestations of pulmonary pathology is shortness of breath. At the initial stages of microlithiasis, this symptom appears only with significant physical exertion – running, rapid ascent of stairs. During the progression of the disease, shortness of breath increases, occurs when walking, the slightest movement.
Cough with pulmonary microlithiasis is moderate, unproductive. A small amount of light mucous sputum is separated. When a bacterial infection is attached, the bronchial secret becomes yellow-green. Sometimes there is hemoptysis. Pain syndrome is not a specific sign of the disease. The patient complains of discomfort, a feeling of heaviness, pressure in the chest. Pain can be localized from one or two sides, there are different degrees of intensity.
The general condition of the body also suffers. The patient experiences increasing feelings of weakness, fatigue, complains of a periodic increase in body temperature to subfebrile and febrile values. Sometimes microlithiasis proceeds latently until the appearance of symptoms characteristic of a chronic pulmonary heart. In the terminal stage of the disease, there are pains in the chest and right hypochondrium. The patient is concerned about heart palpitations, interruptions in the work of the heart. Swelling of the legs joins, respiratory failure progresses sharply. Shortness of breath occurs during conversation and at rest.
Complications of severe alveolar tissue disease occur at stages II-III of the disease. The presence of microliths in the bronchioles and larger bronchi provokes the occurrence of an inflammatory process in the wall of the respiratory tract. With the addition of a secondary infection, bronchitis becomes purulent, bronchopneumonia develops. Progressive hypoxia affects the activity of all organs and systems. Children with microlithiasis lag behind in physical and mental development. The most severe complication leading to the death of the patient is pulmonary heart failure.
Alveolar microlithiasis is one of the most difficult-to-diagnose diseases in pulmonology. When examining a patient with detailed clinical symptoms, signs of chronic, long-term pathology of the respiratory organs are revealed. There is cyanosis of the skin, deformation of the distal phalanges of the fingers by the type of drumsticks, swelling, enlargement of the liver. Percussion and auscultation data are also not specific. In the lower parts of the lungs, moist, small-bubbly and crepitating wheezes can be heard. The following research methods help to confirm the diagnosis:
- Laboratory tests. In a clinical blood test, polycythemia characteristic of pulmonary heart failure is determined. A biochemical study reveals an increased content of calcium and phosphates. Concentric microliths are often found in sputum and bronchial flushing fluid.
- Methods of radiation diagnostics. Chest x-ray show a fine dissemination localized in the lower and middle parts of the lungs and resembling a scattering of sand – a symptom of a “sandstorm”. Numerous small diffuse calcifications are detected on CT scans of the lungs. The accumulation of isotope during perfusion scintigraphy of the lungs confirms the calcification of lung tissue.
- Functional studies. Dynamic examination of the function of external respiration reveals progressive restrictive disorders. The electrocardiogram shows signs of myocardial hypertrophy of the right parts of the heart, tachycardia, extrasystole.
- Lung biopsy. The main method of diagnosis verification. Biopsy sampling is performed during bronchoscopy or transthoracically. In the biopsy material, concentric micro-fragments are found located in the alveoli, bronchial lumen and small bronchi. Excessive deposition of glycogen granules is determined in the walls of the bronchi.
The pulmonologist needs to differentiate alveolar microlithiasis from pulmonary tuberculosis. The early stage of the disease is characterized by scant clinical manifestations against the background of significant radiological changes. Often the disease is mistaken for disseminated tuberculosis of the respiratory system and unsuccessfully treated with anti-tuberculosis drugs. To exclude a specific process, a phthisiatric consultation and sputum examination for Koch bacilli are prescribed.
There are no treatment methods to stop the formation of microliths in the alveolar tissue yet. An experimental search is underway. Symptomatic conservative treatment is prescribed, aimed at reducing the severity of clinical manifestations, improving the quality of life, and relieving infectious complications. Bronchodilators, expectorants, antibacterial and cardiotropic drugs are used. At the last stage of the pathological process, long-term oxygen therapy is performed.
Prognosis and prevention
The prognosis for alveolar tissue microlithiasis is unfavorable. Respiratory heart failure gradually leads to disability and death of the patient. However, the disease usually progresses slowly. Therapeutic and preventive measures help to delay the development of the pulmonary heart somewhat. Patients with an established diagnosis are recommended a healthy lifestyle, smoking cessation, rational employment, vaccination against respiratory infections. It is forbidden to work related to dust, gas pollution, heavy physical exertion.
- Pulmonary alveolar microlithiasis. Romanova LK, Ovcharenko SI, Pokrovskaia MS, Mladkovskaia TB. Arkh Patol. 1995 Mar-Apr;57(2):78-81. link
- Pulmonary alveolar microlithiasis. Sollich V, Kühne W, Thal W, Schuster R. Z Erkr Atmungsorgane. 1987;168(1):77-82. link
- Transbronchial biopsy of pulmonary alveolar microlithiasis. Cale WF, Petsonk EL, Boyd CB. Arch Intern Med. 1983 Feb;143(2):358-9. link
- Pulmonary alveolar microlithiasis: clinical features, evolution of the phenotype, and review of the literature. Castellana G, Gentile M, Castellana R, Fiorente P, Lamorgese V. Am J Med Genet. 2002 Aug 1;111(2):220-4. link
- Pulmonary alveolar microlithiasis. Tachibana T. Ryoikibetsu Shokogun Shirizu. 1994;(4):997-1000. link