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Lymphangioleiomyomatosis
This condition predominantly affects women of reproductive age, causing gradually worsening breathlessness and recurrent lung collapse. It occurs either sporadically or in association with tuberous sclerosis complex, a genetic condition affecting multiple organs.
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Overview
Lymphangioleiomyomatosis, commonly abbreviated as LAM, involves abnormal growth of smooth muscle-like cells within lung tissue, lymphatic vessels, and sometimes the kidneys. These cells cluster together and form nodules that gradually destroy healthy lung architecture, creating numerous thin-walled air-filled spaces called cysts throughout both lungs. Over time, this process impairs the lungs' ability to transfer oxygen into the bloodstream.
The condition affects approximately 3 to 7 women per million population, making it exceptionally rare. Almost all affected individuals are women, typically presenting between ages 20 and 40, though diagnosis sometimes occurs outside this range. LAM exists in two forms: sporadic LAM, which develops without family history, and LAM associated with tuberous sclerosis complex, an inherited condition affecting multiple body systems. Research suggests that hormonal factors may influence disease development and progression, given the strong female predominance and typical onset during reproductive years.
Without treatment, LAM tends to progress gradually, though the rate varies considerably between individuals. Some people experience relatively stable lung function for years, whilst others develop respiratory failure requiring lung transplantation. Advances in targeted therapies over the past decade have significantly improved outcomes for many affected individuals.
Symptoms & clinical features
The most common initial symptom is progressive breathlessness during physical activity, which many people initially attribute to declining fitness or other causes. This breathlessness typically worsens gradually over months to years as cyst formation continues. Many individuals also experience sudden chest pain and breathlessness due to pneumothorax - collapse of part or all of one lung when air leaks from damaged tissue into the chest cavity. Pneumothorax may recur multiple times and sometimes is the first sign prompting medical investigation.
Other respiratory manifestations include persistent cough, sometimes producing blood-tinged sputum, and wheezing similar to asthma. Some individuals develop chylothorax, an accumulation of lymphatic fluid around the lungs causing breathlessness and requiring drainage procedures. Outside the chest, LAM can affect the kidneys, where it may cause angiomyolipomas - benign tumours composed of blood vessels, smooth muscle and fat tissue. These kidney tumours occasionally bleed, causing flank pain and blood in the urine. Lymphatic involvement may also lead to fluid accumulation in the abdomen or swelling in the legs.
Symptom severity varies widely. Some people maintain relatively normal activity levels for many years, whilst others experience rapid deterioration. Factors influencing progression are not fully understood, though evidence suggests earlier diagnosis and treatment initiation may improve long-term outcomes.
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Affected organs
The lungs bear the primary impact of LAM. Abnormal smooth muscle-like cells infiltrate lung tissue diffusely, destroying the delicate alveolar structures responsible for gas exchange. This process creates innumerable cysts ranging from a few millimetres to several centimetres in diameter, scattered throughout both lungs. Unlike some cystic lung diseases that preferentially affect certain lung regions, LAM cysts typically distribute evenly. Progressive cyst formation gradually reduces functional lung tissue, impairing oxygen uptake and carbon dioxide removal.
Beyond the respiratory system, LAM affects lymphatic vessels throughout the chest and abdomen. Abnormal cell growth within lymphatic channels obstructs normal lymph flow, sometimes causing fluid to leak into body cavities or accumulate in tissues. The kidneys are affected in approximately half of individuals with LAM, developing angiomyolipomas that occasionally grow large enough to cause symptoms. Very rarely, similar abnormal cell clusters develop in lymph nodes within the chest or abdomen, though these seldom cause significant problems.
Risks & severity
Disease severity and progression rates vary enormously between individuals. Some people experience relatively stable lung function over decades, whilst others develop respiratory failure within years of symptom onset. On average, lung function declines progressively, though the introduction of targeted therapies has substantially altered disease trajectory. Modern treatments appear to improve outcomes considerably compared to historical observations before these therapies became available.
Pneumothorax represents a major acute risk, occurring frequently in people with LAM at some point during their disease course. Recurrent pneumothorax may necessitate surgical interventions to prevent further episodes. Kidney angiomyolipomas carry bleeding risk, particularly as they grow larger. Massive bleeding from ruptured angiomyolipomas occasionally becomes life-threatening, requiring emergency treatment. Chylothorax, when it develops, can cause significant nutritional problems due to protein and fat loss in drained fluid. Pregnancy may accelerate disease progression in some individuals, though outcomes vary and careful obstetric monitoring enables many women with LAM to carry pregnancies successfully.
Genetic causes
LAM results from pathogenic changes in either TSC1 or TSC2. The TSC1-encoded hamartin protein collaborates with tuberin to restrain cellular proliferation and growth rates. Normal function of this protein partnership prevents cells from multiplying excessively or enlarging beyond appropriate limits. TSC2 encodes tuberin, which works together with hamartin to regulate how rapidly cells divide and what size they attain. Loss of either protein dismantles this growth-control mechanism, permitting unrestrained cell multiplication.
In sporadic LAM, pathogenic variants in TSC2 arise as somatic mutations - genetic changes that occur in specific cells after conception rather than being inherited. These mutations affect only the abnormal smooth muscle-like cells, not the person's entire genetic makeup. Evidence suggests these LAM cells can spread through lymphatic vessels to distant sites, explaining how the condition affects both lungs and sometimes other organs. In LAM associated with tuberous sclerosis complex, individuals inherit a pathogenic TSC1 or TSC2 variant affecting all body cells, predisposing them to develop LAM alongside other tuberous sclerosis features. When variants disrupt TSC1 or TSC2, the resulting deficit in hamartin or tuberin function permits development of non-cancerous tumours affecting multiple organs, a hallmark of tuberous sclerosis complex.
The hamartin-tuberin protein complex normally inhibits a cellular signalling pathway called mTOR, which controls cell growth, protein production and energy metabolism. When TSC1 or TSC2 function is lost, mTOR becomes overactive, driving excessive cell proliferation and survival. This understanding has led to development of mTOR inhibitor drugs that can slow LAM progression by compensating for the lost regulatory function of hamartin and tuberin.
- TSC1 TSC complex subunit 1The TSC1 gene provides instructions for producing hamartin, a protein that plays a vital role in regulating cell growth, proliferation, and size.
- TSC2 TSC complex subunit 2TSC2 encodes tuberin, a tumour suppressor protein that regulates cell growth and division, with pathogenic variants causing tuberous sclerosis complex and related disorders.
Inheritance pattern
Sporadic LAM, which accounts for most cases, is not inherited in families. The pathogenic TSC2 variants responsible arise spontaneously in certain cells and are not passed from parents to children. Children of individuals with sporadic LAM do not have increased risk of developing the condition.
However, when LAM occurs as part of tuberous sclerosis complex, the inheritance pattern is autosomal dominant. This means a pathogenic TSC1 or TSC2 variant in one copy of the gene is sufficient to cause tuberous sclerosis, and each child of an affected parent has a 50% chance of inheriting the variant. People with tuberous sclerosis may develop various features including skin abnormalities, brain lesions causing seizures, kidney angiomyolipomas, and in women, LAM. Not everyone with tuberous sclerosis develops LAM, but women with tuberous sclerosis have substantially elevated LAM risk compared to the general population. Male relatives who inherit tuberous sclerosis variants do not develop LAM, consistent with the condition's strong female predominance.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosis typically begins when chest imaging performed for breathlessness or pneumothorax reveals characteristic diffuse cystic changes throughout both lungs. High-resolution computed tomography scanning shows the cysts particularly clearly, demonstrating their round shape, thin walls, and even distribution - a pattern quite distinct from other cystic lung diseases. In someone presenting with typical imaging findings, particularly a woman of reproductive age with pneumothorax history, LAM is a strong diagnostic consideration.
Confirmation may involve several approaches. Genetic testing of blood samples can identify tuberous sclerosis complex, helping determine whether LAM is sporadic or TSC-associated. Some individuals undergo bronchoscopy or lung biopsy to obtain tissue samples, though this is not always necessary when imaging findings are characteristic. Specialised blood tests measuring a protein called VEGF-D show elevation in many people with LAM and can support diagnosis when combined with appropriate clinical and imaging features. Abdominal imaging to assess for kidney angiomyolipomas provides additional diagnostic information.
In the UK, respiratory physicians typically initiate investigations, with referral to specialist centres experienced in managing rare lung diseases. The NHS Genomic Medicine Service includes LAM within relevant testing pathways, particularly when tuberous sclerosis is suspected. Genetic counselling services can help individuals understand the genetic aspects of their condition and implications for family members.
Management & lifestyle
The mTOR inhibitor sirolimus represents the primary disease-modifying treatment for LAM. This medication partially compensates for the loss of TSC1-TSC2 function by directly inhibiting the mTOR pathway, thereby slowing abnormal cell proliferation. Clinical trials have demonstrated that sirolimus stabilises lung function and reduces complications in many individuals with LAM. Treatment decisions consider disease severity, rate of progression, and individual circumstances, with respiratory specialists experienced in LAM management guiding these choices.
Regular monitoring forms a crucial part of LAM care. Lung function testing at intervals helps track disease progression and treatment response. Chest imaging surveillance detects complications such as pneumothorax early. For individuals with kidney angiomyolipomas, periodic imaging monitors tumour size, with interventions considered if tumours grow large or cause symptoms. When pneumothorax occurs, treatment may include procedures to prevent recurrence, particularly if episodes repeat. Some individuals eventually require supplemental oxygen therapy as lung function declines, whilst a small proportion may be considered for lung transplantation when respiratory failure develops despite medical management.
Lifestyle considerations may include avoiding air travel when pneumothorax risk is particularly high, though many people with LAM travel safely with appropriate precautions. Pulmonary rehabilitation programmes can help maintain physical fitness and quality of life. Some evidence suggests oestrogen-containing medications might influence disease progression, leading many specialists to recommend avoiding hormone replacement therapy and considering alternative contraceptive methods, though these decisions require individualised discussion. Regular follow-up at specialist centres ensures access to evolving treatment options and expertise in managing this complex condition.
UK care pathway
In the UK, LAM diagnosis and management typically occur through respiratory medicine services, often at specialist centres with particular expertise in rare lung diseases. Several centres across England, Scotland, Wales and Northern Ireland have developed LAM services offering multidisciplinary care. Referral to clinical genetics may be appropriate, particularly when tuberous sclerosis complex is suspected or confirmed, enabling genetic testing and family counselling through NHS pathways.
The NHS Genomic Medicine Service includes relevant testing for tuberous sclerosis complex within its rare disease pathways, supporting diagnosis and genetic counselling. Specialist genetic counsellors can help individuals understand the genetic basis of their condition, recurrence risks, and implications for family members. Patient organisations such as LAM Action provide valuable support, connecting individuals with others affected by the condition and offering information resources. Access to these specialist services ensures people with LAM receive coordinated care addressing both respiratory management and broader disease aspects.
Frequently asked questions
Will I definitely need a lung transplant if I have LAM?
No, most people with LAM do not require lung transplantation. Treatment with sirolimus can stabilise lung function in many individuals, and disease progression rates vary considerably. Only a small proportion develop respiratory failure severe enough to warrant transplant consideration.
Can men develop LAM?
Exceptionally rarely, a few cases in men have been reported, almost always associated with tuberous sclerosis complex. The overwhelming majority of people with LAM are women, and the condition's strong female predominance suggests hormonal factors play important roles in its development.
Is it safe for me to become pregnant if I have LAM?
Pregnancy decisions require careful discussion with LAM specialists, as outcomes vary between individuals. Some evidence suggests pregnancy may accelerate disease progression in certain cases, whilst other women navigate pregnancy successfully with close monitoring. Your respiratory team can assess your specific situation and risks.
Does having LAM mean I have tuberous sclerosis?
Not necessarily. Most people with LAM have the sporadic form without tuberous sclerosis. However, evaluation for other tuberous sclerosis features is important, as some individuals have mild tuberous sclerosis that wasn't previously recognised. Your doctors can arrange appropriate assessments.
Will my daughters develop LAM because I have it?
If you have sporadic LAM, your children's risk is not increased - the genetic changes occurred only in your LAM cells and are not inherited. If you have tuberous sclerosis-associated LAM, each child has a 50% chance of inheriting the tuberous sclerosis variant, though not all women with tuberous sclerosis develop LAM.
References
- Bouanzoul MA, Rosen Y. Lymphangioleiomyomatosis: A Review. Archives of pathology & laboratory medicine. 2025. PMID: 39522548
- Johnson SR, Taveira-DaSilva AM, Moss J. Lymphangioleiomyomatosis. Clinics in chest medicine. 2016. PMID: 27514586
- Glassberg MK. Lymphangioleiomyomatosis. Clinics in chest medicine. 2004. PMID: 15331193
- Johnson SR. Lymphangioleiomyomatosis. The European respiratory journal. 2006. PMID: 16707400
- Khaddour K, Sankari A, Shayuk M. Lymphangioleiomyomatosis. 2023. PMID: 30480964
- Kelly J, Moss J. Lymphangioleiomyomatosis. The American journal of the medical sciences. 2001. PMID: 11202475
- McCormack FX. Lymphangioleiomyomatosis. MedGenMed : Medscape general medicine. 2006. PMID: 16915145
- Wang F. Multisystem Lymphangioleiomyomatosis. Radiology. 2024. PMID: 39136570