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What Causes LAM?

The cause of LAM and why it mainly affects women isn’t known. Recent studies show that sporadic LAM has some of the same traits as another rare disease called tuberous sclerosis complex (TSC). This information has provided some valuable clues about what causes LAM.

The common features of sporadic LAM and TSC are:

  • Kidney growths. People who have TSC get growths in their kidneys. These growths are the same as the angiomyolipomas that many women who have LAM get in their kidneys.
  • Lung cysts. Some women who have TSC get cysts in their lungs. These cysts are the same as the ones that women who have sporadic LAM get in their lungs. When a woman who has TSC gets cysts in her lungs, the lung disease is called TSC-associated LAM or TSC–LAM.

TSC is a genetic disease. A defect in one of two genes causes the disease. These genes are called TSC1 and TSC2. They normally make proteins that control cell growth and movement in the body. In people who have TSC, the genes are faulty. The proteins that the genes make can’t control cell growth and movement.

Women who have LAM also have abnormal TSC1 and TSC2 genes. Researchers have found that these genes play a role in causing LAM. This finding is leading to new treatments for LAM.

Because LAM affects women, the hormone estrogen also may play a role in causing the disease.

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LAM Clinical Trials

Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans. To find clinical trials that are currently underway for LAM, visit

December 26, 2013 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.