Pulmonary histiocytosis

Introduction to lung histiocytosis Histiocytosis is a rare group of unexplained diseases, the name of which was proposed by Lichtenstein in 1953. The disease mostly occurs in children, and its pathogenesis, clinical symptoms and pathological range are very different, but the pathologically has a common pathological feature, that is, the abnormal proliferation of histiocytes. It has been confirmed that this tissue cell has Langerhans tissue cells (langerhans' Histocyte) characteristics, so the disease is now known as Langerhans cell histiocytosis. The lung Langerhans cell histiocytosis can originate in the lungs or as part of a systemic systemic lesion. Previously, the name of the disease was more confusing. The focal lesion was called eosinophilic granuloma, while the systemic lesion was called letter-Siwe disease (Lee-Snow disease) and Hand-Schüller-Christian disease (Han- Xu-ke disease). In order to avoid confusion, the American Society of Cellular Sciences proposed a new classification method for such diseases in 1997, depending on the organ involvement. basic knowledge The proportion of illness: 0.0035% Susceptible people: more than children Mode of infection: non-infectious Complications: pneumothorax

Causes of pulmonary histiocytosis

(1) Causes of the disease

The cause is unknown.

(two) pathogenesis

1. Pathological manifestations The typical pathological change of lung histiocytosis is that activated Langerhans cells constitute a loose granulomatous tissue, which is accompanied by lymphocytes and inflammatory cell infiltration, the latter mainly including eosinophils and giants. The morphology of Langerhans cells in phagocytic and granulomatous tissues is similar to that of Langerhans cells in normal tissues. It is medium-sized and has a diameter of about 15 m. The cell boundaries are not clear, and the nucleus is a typical irregular shape. And the folding is obvious, the cytoplasm is pale, mild eosinophilic, the cell nucleus is obvious under electron microscope, and the cytoplasm contains well-differentiated Golgi and abundant endoplasmic reticulum and mitochondria. The characteristic change is that Birbeck can be seen under electron microscope. Langerhans cells on granulomatous tissue express class I and class II histocompatibility antigens, 2 integrin (CDlla/CDllc/CD18), adhesin (CD54, CD58), leukocyte common antigen (CD45 RO) and cells Intra-S-100 protein, etc., lung Langerhans cell granulomatous lesions are focally distributed, separated by normal lung tissue, they are in the center of the distal bronchioles Infiltration and destruction of the tracheal wall, in this sense, the lung Langerhans cell granuloma should be a bronchiole disease rather than diffuse interstitial lung disease, granuloma and adjacent tissue boundaries are unclear, granulomas can be Adjacent alveolar expansion, the surrounding alveolar cavity contains a large number of macrophages (like desquamative interstitial pneumonia, DIP) accompanied by Langerhans cells, granulomatous lesions around the lymphocyte infiltration, which is large Part of the CD4 / T lymphocytes, lung tissue that is not invaded by granulation tissue is usually normal, but there are usually some non-specific changes in these lung tissues due to smoking.

2. Other mechanisms Recent studies have shown that Langerhans cells in Langerhans cell histiocytosis (LCH) are of clonal origin, suggesting that these cell abnormalities play an important role in the pathogenesis of LCH, normal lung Gehans cells usually appear only in the mucosal epithelium of the bronchi, while granulomatous lesions of the LCH in the lung are usually located in the center of the bronchiole, suggesting that the microenvironment of the bronchial epithelium may play an important role in determining the aggregation of Langerhans cells. Because smoking is closely related to lung LCH, and smoking is the most obvious damage to bronchial epithelium, it is believed that bronchial epithelial damage caused by smoking may be related to the accumulation of Langerhans cells in the lung. Epithelial cells can produce many abilities when stimulated. Cytokines that influence the proliferation, differentiation, and longevity of Langerhans cells (such as granulocyte monocyte colony-stimulating factor, GM-CSF). From this perspective, epithelial cells produce excessive cytokines that may be in the lung LCH. It plays an important role in the initial process. In addition, other airway epithelial cells such as neuroendocrine cells produce more media such as frog skin. It may also play a role in the pathogenesis of lung LCH. Because the bronchial epithelium is rapidly destroyed in the LCH of the lung, it indicates that the epithelial cells are not a continuous factor of Langerhans cell proliferation, and the Langerhans cells in the lung LCH can Through autocrine or paracrine functions, the production of a variety of cytokines including GM-CSF, TNF-, IL-1, IL-6, etc. may play an important role in maintaining the continuous development of lung LCH.

Regardless of the role of smoking in the pathogenesis of LCH, only a small percentage of smokers are afflicted with this disease, suggesting that there are other factors involved in the pathogenesis. Recently, some scholars have discovered through the X-chromosome degradation process in female patients, whether it is bureau The Langerhans cells in the focal lesions or the Langerhans cells in the diffuse lesions all originated from the same clone, suggesting that LCH may be similar to tumors due to the proliferation of Langerhans cell clones. In addition, Lange The chromosomal mutation of the precursor cells of Hans cells may also play a role in the pathogenesis of LCH. It is believed that the cloning markers on the surface of Langerhans cells are necessary for the occurrence of LCH, but their functional behavioral abnormalities are more malignant than tumors. Light, for example, mutations can cause the Langerhans cell precursor cells to respond to the signalling of normal cytokines, leading to the clonal propagation of the precursor cells of Langerhans cells, which, with constant differentiation, Gehans cells gradually lose their ability to regenerate, but they still retain some abnormalities in clinical manifestations, such as the signal to chemotactic factors. The enhancement of the response and the decrease of the degree of apoptosis. In summary, the pathogenesis of LCH is still unclear. Further understanding of the molecular biological mechanism of Langerhans cell clonal proliferation is of great significance for elucidating the pathogenesis of LCH.

Lung histiocytosis prevention

1. Avoid contact with harmful factors to avoid exposure to harmful chemical substances, especially drugs. Pay attention to rational use of drugs, and when exposed to poisons or radioactive materials, various protective measures should be strengthened.
2. Vigorously carry out missionary activities to prevent and treat various infectious diseases, especially viral infections.
3, strengthen physical exercise, pay attention to food hygiene, maintain a comfortable mood, work and rest, enhance the body's resistance.

Pulmonary histiocytosis complications Complications

Can be complicated by spontaneous pneumothorax and respiratory failure, pulmonary heart disease can occur in the late stage.

Pulmonary histiocytosis symptoms Common symptoms Weak dry cough, dyspnea, hemoptysis, chest pain, bone pain, mucosal proliferative inflammation

Lung Langerhans histiocytosis can occur at any age, multi-organ and multi-system Langerhans cell histiocytosis usually in infants and children, but lung involvement is usually not the main clinical manifestation, on the contrary, only involving the lungs The lung Langerhans cell histiocytosis mostly occurs in the 20-40 age group, there is no significant gender difference, the clinical manifestations of pulmonary Langerhans cell histiocytosis are very different, about 25% of patients have no clinical symptoms, only Occasionally, during the physical examination, some patients found that after pneumothorax or respiratory symptoms, X-ray examination, the most common symptoms of patients are dry cough (56% to 70%) and dyspnea (40%), other clinical symptoms. Including chest pain (10% to 20%), fatigue (30%), weight loss (20% to 30%), fever (15%), about half of patients have a history of rhinitis before onset, hemoptysis is less than 5% About 25% of patients can have recurrent pneumothorax.

4% to 20% of patients may have cystic lesions of the bone. Patients usually have focal bone pain or pathological fractures. A small number of patients (about 15%) may have central nervous system involvement and suggest a poor prognosis.

Physical examination: Generally no obvious abnormal findings, "popping sound" and "skull finger" are generally uncommon, secondary pulmonary hypertension can be seen, but often overlooked, pulmonary heart disease can occur in the late stage of the disease.

Examination of lung histiocytosis

Routine laboratory tests usually have no positive findings, peripheral blood eosinophil counts are normal, routine blood biochemical tests are usually found without abnormalities, peripheral blood eosinophils are usually normal, erythrocyte sedimentation rate is generally moderate, patients often There are a variety of low titers of autoantibodies and immune complexes present, and serum angiotensin converting enzyme is normal.

1. X-ray findings Chest X-ray performance varies according to the different stages of the disease. The lesions are usually bilaterally symmetrical. Although the lesions are diffuse, they are mainly concentrated in the upper middle lung field. Blurred small nodule shadows (less than 5mm in diameter) are characteristic changes. The most common change is reticular nodules, sometimes cystic lesions coexist. In the advanced stage, nodular shadows usually disappear, replaced by lung sacs. Sexual changes and even pseudo-emphysema formation, other manifestations can be differentiated from other diffuse lung diseases, including changes in lung volume, lesions located in the upper part of the lungs, no mediastinal lymphadenopathy and pleural involvement, and some patients may have repeated Pneumothorax and rib osteolytic changes, but it should be noted that less than 19% of patients with chest X-ray examination can be completely normal.

2. Chest CT high-resolution CT (HRCT) is not only meaningful for the differential diagnosis of the disease, but also has a certain significance in judging the severity of the disease. The lesion is usually distributed in the middle of normal lung tissue, although in the base of the lower lung. The scattered lesions can be seen, but the lesions are mostly located in the upper part, and the symmetry is evenly distributed. The early lesions are mainly dominated by small nodular shadows with blurred borders. In some cases, there are cavities formed, and the nodules are centrally distributed by the lobules, and With cystic changes of thin wall thickness, as the lesion progresses, cystic changes gradually become prominent. These capsules vary greatly in size, but usually less than 1 cm in diameter, the capsule can be isolated or fused. Even the appearance of emphysema, spontaneous small nodules, cavities and cysticization are characteristic changes of lung Langerhans cell histiocytosis.

3. Pulmonary function test The lung function of lung Langerhans cell histiocytosis is related to the extent of lung lesion involvement, which can be obstructive, restrictive and mixed ventilatory dysfunction. 10% to 15% of patients have lung function. Normally, although chest X-ray findings have been found to be abnormal, the more common change is a decrease in vital capacity (VC) and an increase in residual gas volume (RV), so the total lung volume is normal and the RV/TLC ratio is increased. Functional changes are associated with cysticization of the patient's lungs. About 50% of patients have obstructive ventilatory dysfunction, which is characterized by a decrease in FEV1. If a patient with diffuse pulmonary interstitial disease has obstructive ventilatory dysfunction, it is a very useful diagnosis. In the lung Langerhans cell histiocytosis index, the most common lung function change is the decrease of diffuse function. The arterial oxygen partial pressure can be normal or mildly reduced at rest, but exercise hypoxemia is the most common.

4. Fiberoptic bronchoscopy and bronchoalveolar lavage examination bronchoscopy can be seen in normal or non-specific bronchial mucosal changes, bronchial biopsy is not helpful for diagnosis, transbronchial lung biopsy usually because the biopsy tissue is too small, the diagnosis is not meaningful Large, but if the biopsy tissue is large enough to detect Langerhans cells using immunohistochemical techniques, it is important for diagnosis. In most patients, the total number of cells in the bronchoalveolar lavage fluid (BALF) is increased. The classification of cells is mainly due to the increase of neutrophils and eosinophils, and the ratio of CD4/CD8 is decreased. For example, Langerhans cells are more than 5%, which strongly suggests the possibility of pulmonary Langerhans cell histiocytosis. .

Diagnosis and diagnosis of lung histiocytosis

Affirmative diagnosis relies on pathological examination. Although fiberoptic bronchoscopy can sometimes confirm the diagnosis, the diagnosis rate of open lung biopsy is better than that of transbronchial lung biopsy. The history and physical examination are generally non-specific. The medical history is helpful for diagnosis, but it is not unique. Chest CT examination has certain significance for typical cases, but atypical performance cannot completely rule out the diagnosis.

It should be differentiated from chronic exogenous pneumonia, non-lymphangiomyelia and Wegener's granulomatosis.

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