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What is LAM? How does this progressive lung disease destroy your lungs?
Lymphangioleiomyomatosis (LAM) is a rare and progressive systemic disease that often results in cystic lung destruction. This condition mainly affects women, especially those of childbearing age. Based on the etiology, LAM can be divided into two categories: LAM associated with tuberous sclerosis complex (TSC) (TSC-LAM) and sporadic LAM not associated with TSC.
Symptoms and signs
The average age of onset of LAM is around 30 to 40 years old. The initial symptoms were mostly exertional dyspnea and spontaneous pneumothorax, which occurred in 49% and 46% of patients respectively. Diagnosis is often delayed by 5 to 6 years, and the disease is often misdiagnosed as asthma or chronic obstructive pulmonary disease. The consensus clinical definition of the disease includes multiple symptoms: fatigue, cough, hemoptysis (rarely in large amounts), chest pain, and various lymphatic complications such as chylothorax, lymph node or other lesions caused by lymphatic obstruction. About 30% of patients with sporadic LAM and 90% of patients with TSC-LAM develop angiomyolipomas.
Lung destruction is the result of LAM, with tumor-like smooth muscle cells spreading and invading all lung structures, including lymphatics, airways, blood vessels, and interstitial spaces.
Genetics
LAM occurs in two scenarios: one is TSC-LAM under TSC, and the other is sporadic LAM without TSC. Both diseases show inactivating or "loss-of-function" mutations in the TSC1 or TSC2 genes as the underlying cause of LAM. Mutational changes in the TSC gene can cause LAM cells in the cells to proliferate rapidly, subsequently causing major damage to the lungs.
Physiology and pathology
In LAM lesions, the proportion of cells containing mutations in tuberous sclerosis (TSC1 or TSC2) tumor suppressor genes changes. This triggered research on the mTOR pathway and the use of the inhibitor sirolimus (an analogue of rapamycin) to treat LAM, which has been clinically applied.
Loss of TSC1/TSC2 results in disordered growth and increased survival of LAM cells, which behave in many ways like metastatic tumor cells.
Diagnostic methods
There are many ways to diagnose LAM. Chest CT scan is usually the key examination, and thin-walled cystic changes may be discovered incidentally during other examinations. In particular, in patients who frequently develop spontaneous pneumothorax, Chest CT scans often reveal typical changes in the lungs. In some cases, clinical diagnosis can be determined based on accompanying imaging features (such as TSC, liponephroma, etc.) without the need for biopsy.
Treatment Plan
Currently, the FDA has approved a drug for the treatment of LAM, the mTOR inhibitor sirolimus, which can effectively stabilize the decline in lung function. For terminally ill patients, lung transplantation is the last option.
Patients with solid tumors often crave effective treatment options because their quality of life and survival are severely affected. LAM patients are no exception. The treatment they pursue is not only survival, but also the ability to restore life.
In progressive diseases such as LAM, can early detection and response strategies change the fate of patients? This is a question worth pondering.
