Reviewed by National Heart Lung and Blood Institute.

The precise cause of lymphangioleiomyomatosis, or 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 has begun to provide 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. About 1 out of every 3 women who has TSC gets cysts in her 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 these 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 abnormal. 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 mostly affects women, the hormone estrogen also may play a role in causing LAM.

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