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The mystery of LAM lung disease: Why is this rare disease often misdiagnosed?
Lymphangioleiomyomatosis (LAM) is a rare and progressive systemic disease that typically causes cystic destruction of the lungs. This disease mainly affects women, especially those of childbearing age, and due to the diversity of its symptoms, diagnosis is often delayed, which makes LAM patients feel helpless when facing the disease.
In many cases, the diagnosis of LAM may be delayed by 5 to 6 years and is often misdiagnosed as asthma or chronic obstructive pulmonary disease (COPD).
Signs and symptoms
The average age of onset of LAM disease is approximately 30 to 40 years, and the most common symptoms include exertional tachypnea and spontaneous pneumothorax. In some people, these symptoms may precede diagnosis.
82% of LAM patients had experienced at least one pneumothorax before diagnosis.
Other symptoms may include fatigue, cough, coughing up blood (rarely large amounts), and complications related to the lymphatic system, such as swollen lymph nodes and chylothorax. Fatty renal tumors (angiomyolipomas) may develop in approximately 30% of patients with sporadic LAM and in up to 90% of patients with LAM associated with tuberous sclerosis complex. These tumors sometimes bleed spontaneously, causing pain or low blood pressure.
Genetics and Pathophysiology
There are two main types of LAM: tuberous sclerosis complex (TSC)-associated LAM (TSC-LAM) and independent sporadic LAM. In both cases, LAM is caused by inactivating mutations in the TSC1 or TSC2 genes. These genes are responsible for regulating the mammalian mTOR (target of rapamycin) signaling pathway, thereby affecting cell proliferation.
Studies have shown that LAM cells can migrate from one location to another, supporting the "benign metastasis" hypothesis.
Diagnostic Methods
The diagnostic process of LAM is often complicated by the diverse clinical manifestations. Initial workup often results in a chest CT scan, and thin-walled cystic changes may be discovered inadvertently. A definitive diagnosis of LAM usually requires a high-resolution CT scan, in which the most characteristic feature is the presence of bilateral thin-walled cysts.
In addition to CT scans, lung function tests are one of the main tools for diagnosis. Because patients with LAM may have normal lung function or obstructive, restrictive, or mixed ventilation patterns, pulmonary function testing is essential.
Treatment Options
Currently, the FDA has approved the mTOR inhibitor sirolimus for the treatment of LAM and can be used to stabilize the decline in lung function. For advanced patients, lung transplantation remains the last option.
In addition, for patients with concomitant pneumothorax, it is recommended to consider pleural healing after the first pneumothorax. Because more than 65% of LAM patients will develop pneumothorax during the course of the disease, effective management strategies are crucial to improve patients' quality of life.
ConclusionAs a rare lung disease, LAM faces great challenges in diagnosis. The diversity of symptoms and similar presentation to other lung diseases often lead to it being misdiagnosed. This reminds us that when faced with unexplained dyspnea or other lung symptoms, should we be more cautious in seeking further examination and diagnosis?
