LAM most commonly refers to lymphangioleiomyomatosis, a rare lung disease that primarily affects women of childbearing age. It causes cysts to form throughout the lungs, gradually reducing the ability to breathe. LAM can also stand for the lactational amenorrhea method, a form of natural birth control used during breastfeeding. This article covers both meanings so you can find the answer you’re looking for.
LAM as a Lung Disease
Lymphangioleiomyomatosis is a progressive condition in which abnormal smooth muscle-like cells grow in the lungs, airways, and lymphatic system. These cells, called LAM cells, multiply and obstruct the small airways, leading to air trapping, cyst formation, and gradual destruction of lung tissue. The cysts are visible on CT scans as round, thin-walled air spaces scattered evenly through both lungs, ranging from a few millimeters to 5 centimeters across.
Part of the damage comes from an imbalance in the enzymes that maintain lung structure. LAM cells produce excess amounts of proteins that break down the elastic tissue in the lungs faster than the body can repair it, which is what creates the characteristic holes.
Who Gets LAM and Why
LAM occurs in two forms. Sporadic LAM appears in women with no family history of the disease, while TSC-associated LAM develops in people who have tuberous sclerosis complex, a genetic condition that causes benign tumors in multiple organs. Despite arising differently, the two forms look identical under a microscope and behave the same way in the lungs.
Both forms trace back to mutations in the TSC2 gene on chromosome 16, which normally acts as a tumor suppressor, keeping cell growth in check. When TSC2 stops working, it triggers overactivity in a cellular growth pathway called mTOR, essentially removing the brakes on cell multiplication. In sporadic LAM, these mutations happen spontaneously in the body’s cells rather than being inherited. Researchers confirmed this by finding the same TSC2 mutation in both kidney tumors and lung tissue from the same patients, proving that a single genetic event drives the disease in multiple organs.
Symptoms and First Signs
The most common symptom is shortness of breath during physical activity, which worsens over time as more cysts develop. Coughing, wheezing, and chest pain also occur. Because these symptoms overlap with asthma and other common conditions, LAM is frequently misdiagnosed for years.
A collapsed lung (pneumothorax) is often what finally leads to a diagnosis. About 50 to 60 percent of women with LAM experience at least one pneumothorax during their lifetime, and in roughly a third of those cases, it’s the event that first brings the disease to medical attention. A young woman with a spontaneous collapsed lung and no obvious risk factors like smoking should be evaluated for LAM.
How LAM Is Diagnosed
A high-resolution CT scan of the chest is the primary diagnostic tool. The pattern of numerous round, thin-walled cysts distributed uniformly through both lungs is distinctive enough to strongly suggest LAM, especially in a woman of reproductive age.
A blood test measuring a protein called VEGF-D can often confirm the diagnosis without a lung biopsy. About 70 percent of women with LAM have elevated levels of this protein. A VEGF-D level above 800 pg/mL identifies LAM with 100 percent specificity, meaning if the level is that high, the diagnosis is essentially certain. Even at a lower threshold of 600 pg/mL, the test is 98 percent specific with 84 percent sensitivity. This blood test has made invasive biopsies unnecessary for many patients.
Kidney Tumors and Other Complications
LAM doesn’t only affect the lungs. Between 20 and 54 percent of women with the disease develop kidney growths called angiomyolipomas, which are benign tumors made of fat, smooth muscle, and blood vessels. These tumors share the same TSC2 mutation as the lung disease, confirming they’re part of the same underlying process. Most angiomyolipomas are small and cause no symptoms, but larger ones can bleed and may need treatment.
Pregnancy poses particular challenges. It has been associated with faster disease progression and a higher risk of collapsed lungs. The exact level of risk for any individual patient is hard to predict, but women with well-preserved lung function are generally better positioned to carry a pregnancy than those whose breathing is already significantly impaired.
Treatment and Long-Term Outlook
Because the mTOR pathway drives LAM cell growth, drugs that block this pathway have become the standard treatment. These medications slow cyst formation and stabilize lung function in many patients, and VEGF-D levels in the blood can help track whether treatment is working.
Without treatment, lung function declines by an average of about 90 milliliters per year as measured by a standard breathing test. To put that in perspective, a healthy adult might have a total lung capacity measurement of around 3,000 to 4,000 milliliters, so this represents a meaningful annual loss. With current therapies, the prognosis has improved substantially. Average survival from the time of diagnosis now exceeds 25 years. Five-year transplant-free survival is 94 percent, dropping to 85 percent at 10 years, 75 percent at 15 years, and 64 percent at 20 years. For patients whose disease eventually becomes severe, lung transplantation remains an option.
LAM as a Birth Control Method
The other common meaning of LAM is the lactational amenorrhea method, a natural form of contraception based on the fact that breastfeeding suppresses ovulation. When used correctly, it is about 98 percent effective, but only when all three of the following criteria are met simultaneously:
- Your period has not returned since giving birth
- You are fully or nearly fully breastfeeding, with no gaps longer than 4 hours during the day or 6 hours at night
- Your baby is less than 6 months old
If any one of these conditions changes, such as your period returning, supplementing with formula, or your baby reaching 6 months, LAM is no longer reliable and you would need a different contraceptive method. The effectiveness drops significantly once any criterion is broken, so this approach works only as a short-term strategy in the early months of exclusive breastfeeding.