Danbot: Strip excess bold

2026-03-22T09:28:55Z

Strip excess bold

Danbot: Moved intro into Background as bullets; removed excessive bold from bullet lead-ins; added Pulmonary fibrosis differential and SOB DDX templates

2026-03-19T14:41:32Z

Moved intro into Background as bullets; removed excessive bold from bullet lead-ins; added Pulmonary fibrosis differential and SOB DDX templates

Show changes

Ostermayer: Created page with "Lymphangioleiomyomatosis (LAM) is a rare, progressive, low-grade neoplastic lung disease characterized by infiltration of abnormal smooth muscle-like cells (LAM cells) into the lung parenchyma, lymphatics, and blood vessels, resulting in '''diffuse thin-walled cystic destruction''' of both lungs.Lymphangioleiomyomatosis. ''StatPearls''. NCBI Bookshelf. Updated June 2023. It almost exclusively affects '''women of childbearing age''' (mean diag..."

2026-03-11T12:14:31Z

Created page with "Lymphangioleiomyomatosis (LAM) is a rare, progressive, low-grade neoplastic lung disease characterized by infiltration of abnormal smooth muscle-like cells (LAM cells) into the lung parenchyma, lymphatics, and blood vessels, resulting in '''diffuse thin-walled cystic destruction''' of both lungs.<ref name="StatPearls">Lymphangioleiomyomatosis. ''StatPearls''. NCBI Bookshelf. Updated June 2023.</ref> It almost exclusively affects '''women of childbearing age''' (mean diag..."

New page

Lymphangioleiomyomatosis (LAM) is a rare, progressive, low-grade neoplastic lung disease characterized by infiltration of abnormal smooth muscle-like cells (LAM cells) into the lung parenchyma, lymphatics, and blood vessels, resulting in '''diffuse thin-walled cystic destruction''' of both lungs.<ref name="StatPearls">Lymphangioleiomyomatosis. ''StatPearls''. NCBI Bookshelf. Updated June 2023.</ref> It almost exclusively affects '''women of childbearing age''' (mean diagnosis ~35 years). LAM cells harbor mutations in '''tuberous sclerosis complex (TSC)''' genes causing constitutive activation of the '''mTOR pathway'''.<ref name="Lancet">McCormack FX, et al. Lymphangioleiomyomatosis: pathogenesis, clinical features, diagnosis, and management. ''Lancet Respir Med''. 2021.</ref> ED physicians will most commonly encounter LAM patients presenting with '''recurrent spontaneous [[pneumothorax]]''', '''chylous pleural effusion''', or progressive dyspnea — and the diagnosis may not yet be established.

==Background==
*LAM occurs in two forms:<ref name="StatPearls"/>
**'''Sporadic LAM (S-LAM):''' Somatic TSC2 mutations; ~3.4–7.8 per million women; no family inheritance
**'''TSC-associated LAM (TSC-LAM):''' 30–40% of women with tuberous sclerosis develop LAM; autosomal dominant TSC1 or TSC2 germline mutations
*LAM cells are neoplastic smooth muscle-like cells that express smooth muscle actin, '''HMB-45''' (melanocytic marker — key for pathologic diagnosis), and estrogen/progesterone receptors<ref name="ERS2010">Johnson SR, et al. European Respiratory Society guidelines for the diagnosis and management of lymphangioleiomyomatosis. ''Eur Respir J''. 2010;35(1):14-26.</ref>
*'''Estrogen dependence:''' LAM almost exclusively affects premenopausal women; may accelerate during pregnancy and with exogenous estrogen; decelerates after menopause<ref name="StatPearls"/>
*'''Pathogenesis:''' TSC gene mutations → loss of hamartin/tuberin tumor suppressor complex → constitutive mTORC1 activation → uncontrolled cell proliferation, lymphangiogenesis, and cystic lung destruction<ref name="Lancet"/>
*LAM cells metastasize via the lymphatics (LAM is considered a low-grade metastasizing neoplasm with likely uterine origin)<ref name="Lancet"/>
*Proliferation of LAM cells obstructs bronchioles (→ air trapping, bullae, [[pneumothorax]]), lymphatics (→ chylous effusions), and venules (→ hemoptysis)<ref name="Medscape">Lymphangioleiomyomatosis. ''Medscape/eMedicine''. Updated 2024.</ref>
*'''Extrapulmonary manifestations:'''
**'''Renal angiomyolipomas (AML):''' Present in ~30–40% of S-LAM and ~80% of TSC-LAM; benign fat-containing tumors; may hemorrhage (especially >4 cm)<ref name="ERS2010"/>
**'''Lymphangioleiomyomas:''' Cystic masses of the axial lymphatics; abdominopelvic lymphadenopathy
**'''Chylous effusions:''' Chylothorax (~20%) and/or chylous ascites from lymphatic obstruction<ref name="LAMFound">LAM Management. The LAM Foundation. Updated October 2023.</ref>
**Increased frequency of meningiomas<ref name="ERS2010"/>
*'''Epidemiology:''' ~3.4–7.8 per million women (sporadic LAM); prevalence likely underestimated due to delayed diagnosis (average 5–6 years from symptom onset)<ref name="StatPearls"/>
*FEV1 declines at ~75–118 mL/year in untreated patients<ref name="MILES">McCormack FX, et al. Efficacy and safety of sirolimus in lymphangioleiomyomatosis. ''N Engl J Med''. 2011;364(17):1595-1606.</ref>
*>90% 10-year survival with modern management<ref name="ClevelandClinic">Lymphangioleiomyomatosis (LAM). Cleveland Clinic. Updated December 2025.</ref>

==Clinical Features==
*'''Progressive exertional dyspnea''' — the most common symptom; insidious onset; often attributed to [[asthma]] or deconditioning for years before diagnosis<ref name="StatPearls"/>
*'''Recurrent spontaneous [[pneumothorax]]:'''<ref name="Lancet"/>
**Occurs in ~66% of LAM patients during their lifetime
**'''Presenting manifestation in ~25%''' of patients — this is often how LAM is first diagnosed
**'''Recurrence rate >70%''' if managed conservatively (observation/aspiration alone)
**Lifetime average of 3–4 pneumothoraces per patient
**May be bilateral or alternating sides
*'''Chylous pleural effusion (chylothorax):''' ~20% of patients; milky fluid; elevated triglycerides (>110 mg/dL)<ref name="LAMFound"/>
*'''Hemoptysis:''' Usually mild; from venule obstruction by LAM cells
*Cough (often nonproductive)
*Fatigue
*'''Wheezing:''' ~20–25% of LAM patients have a reversible obstructive (asthma-like) component responsive to bronchodilators<ref name="LAMFound"/>
*'''Physical exam''' is often '''unremarkable''' early in disease
**Advanced disease: decreased breath sounds, scattered wheezes, hyperresonance
**Absent breath sounds unilaterally → pneumothorax or large effusion
**Abdominal mass → lymphangioleiomyoma or hemorrhaging AML
**Signs of tuberous sclerosis: facial angiofibromas, ungual fibromas, shagreen patches, hypomelanotic macules, cortical tubers
*'''ED red flags suggesting LAM in a previously undiagnosed patient:'''
**Young woman with '''recurrent''' spontaneous pneumothorax (especially bilateral or alternating)
**Spontaneous pneumothorax in a woman with known tuberous sclerosis
**'''Chylous''' (milky) pleural effusion in a young woman
**Diffuse bilateral cysts found incidentally on chest CT performed for other reasons
**Retroperitoneal hemorrhage from ruptured renal AML

==Differential Diagnosis==
'''Diffuse cystic lung diseases''' (the primary radiologic differential):<ref name="Lancet"/>
*Pulmonary Langerhans cell histiocytosis (cysts + nodules; '''spares costophrenic angles'''; smoker; irregularly shaped cysts)
*Lymphocytic interstitial pneumonia (LIP — cysts with ground-glass opacities; associated with [[Sjögren syndrome]] and [[HIV]])
*Birt-Hogg-Dubé syndrome (autosomal dominant; cysts predominantly '''basilar and medial'''; renal tumors are chromophobe or oncocytoma, not AML; skin fibrofolliculomas)
*'''Emphysema''' ([[COPD]]) — older, smoker; centrilobular distribution; no true thin walls
*[[Amyloidosis]] (rare cystic form)
*Light-chain deposition disease

'''Other causes of recurrent pneumothorax in young women:'''
*Catamenial [[pneumothorax]] (related to menstrual cycle; thoracic [[endometriosis]])
*Alpha-1 antitrypsin deficiency
*[[Marfan syndrome]]
*[[Ehlers-Danlos syndrome]]

'''Other:'''
*[[Asthma]] (often initial misdiagnosis; LAM has irreversible obstruction)
*[[Sarcoidosis]]
*[[Hypersensitivity pneumonitis]]
*Metastatic disease with cystic lung change (rare)

{{SOB DDX}}

==Evaluation==
===Workup===
'''Laboratory (ED):'''
*CBC, [[basic metabolic panel]], lactate
*ABG/VBG: hypoxemia in advanced disease or acute pneumothorax
*'''Pleural fluid analysis''' if thoracentesis performed: '''chylous effusion''' — milky/turbid; '''triglycerides >110 mg/dL''' is diagnostic of chylothorax; '''cholesterol/triglyceride ratio <1''' distinguishes chyle from pseudochylothorax; lymphocyte-predominant<ref name="StatPearls"/>
*'''Serum VEGF-D (vascular endothelial growth factor-D):''' Not an ED test, but understand its role — '''≥800 pg/mL is 100% specific''' for LAM in the setting of compatible cystic lung disease on CT; eliminates need for biopsy in most cases; low levels (<800 pg/mL) do '''not''' exclude LAM (high false-negative rate)<ref name="StatPearls"/>
*If renal AML suspected (flank pain, hematuria, retroperitoneal hemorrhage): hemoglobin/hematocrit, type and screen, renal function, urinalysis

'''Imaging:'''

''Chest X-ray:''
*May be '''normal''' early in disease
*Increased lung volumes (hyperinflation) — unlike most ILDs which cause volume loss
*Reticulonodular pattern
*Pneumothorax
*Pleural effusion
*'''Preserved or increased lung volumes despite diffuse interstitial changes''' is a key clue (most ILDs cause volume loss; LAM causes hyperinflation from air trapping)

''HRCT — the key diagnostic imaging study:''
*'''Diffuse, bilateral, round or ovoid, thin-walled cysts''' distributed uniformly throughout both lungs — the hallmark finding<ref name="StatPearls"/>
*Cysts are typically '''2–5 mm''' but can range from 1 mm to 30 mm
*'''No zonal predominance''' (cysts affect upper, middle, and lower zones equally) — distinguishes from Langerhans cell histiocytosis (upper-zone predominant, spares bases) and Birt-Hogg-Dubé (basilar/medial)
*Intervening lung parenchyma appears '''normal''' (no ground-glass opacities, nodules, or consolidation)
*Ground-glass opacities suggest alternative or superimposed diagnosis
*May also show: pneumothorax, pleural effusion, mediastinal/hilar lymphadenopathy, pericardial effusion
*'''HRCT alone is NOT sufficient for definitive diagnosis''' per ATS/JRS 2017 guidelines — requires additional confirmatory features (see Diagnosis below)<ref name="ATS2017">Gupta N, et al. Lymphangioleiomyomatosis diagnosis and management: HRCT, transbronchial lung biopsy, and pleural disease management. An official ATS/JRS clinical practice guideline. ''Am J Respir Crit Care Med''. 2017;196(10):1337-1348.</ref>

''CT abdomen/pelvis (coordinate with inpatient/outpatient team):''
*Renal angiomyolipomas: '''fat-containing''' renal masses (classically fat-density on CT); may be bilateral and multiple; risk of hemorrhage if >4 cm
*Retroperitoneal lymphangioleiomyomas
*Lymphadenopathy
*Chylous ascites

'''Pulmonary function tests''' (outpatient — understand the pattern):
*'''Obstructive''' or '''mixed obstructive-restrictive''' pattern (unlike most ILDs which are purely restrictive)<ref name="StatPearls"/>
*Reduced FEV1, reduced FEV1/FVC ratio
*Reduced DLCO (often the earliest abnormality)
*Increased residual volume (air trapping)
*~20–25% have bronchodilator responsiveness<ref name="LAMFound"/>

===Diagnosis===
*'''Definitive diagnosis of LAM''' can be made '''without biopsy''' when characteristic cystic lung disease on HRCT is present '''plus''' any ONE of the following:<ref name="StatPearls"/>
**(1) Diagnosis of tuberous sclerosis
**(2) Serum VEGF-D '''≥800 pg/mL'''
**(3) Renal angiomyolipoma (confirmed by imaging)
**(4) Lymphangioleiomyoma
**(5) Chylous effusion (pleural or ascitic)
*'''HRCT findings alone are insufficient''' for definitive diagnosis (per ATS/JRS 2017) due to overlap with other cystic lung diseases; requires confirmatory clinical, radiologic, or serologic feature<ref name="ATS2017"/>
*If no confirmatory features: consider transbronchial lung biopsy (HMB-45 staining is highly specific) or surgical lung biopsy<ref name="ATS2017"/>
*'''In the ED:''' The goal is not to definitively diagnose LAM, but to recognize the pattern (young woman + recurrent pneumothorax + diffuse cysts on CT) and ensure appropriate referral

==Management==
'''ED management is primarily supportive and complication-directed:'''

'''1. Pneumothorax management:'''
*Treat per standard [[pneumothorax]] protocols: observation for small pneumothorax without respiratory distress; '''chest tube thoracostomy''' (pigtail or surgical) for symptomatic or large pneumothorax<ref name="LAMFound"/>
*'''Critical LAM-specific point:''' Recurrence rate is >70% with conservative management alone; ATS/JRS guidelines recommend '''pleurodesis after the FIRST pneumothorax''' rather than waiting for recurrence<ref name="ATS2017"/>
*VATS-guided mechanical abrasion is the preferred initial pleurodesis modality; chemical pleurodesis (talc) is reserved for recurrence after initial pleurodesis<ref name="LAMFound"/>
*'''Prior pleurodesis is NOT a contraindication for future lung transplantation''' (ATS/JRS 2017) — this is critical to know, as outdated teaching suggested otherwise and may cause clinicians to delay pleurodesis<ref name="ATS2017"/>
*Consult thoracic surgery early for patients with known or suspected LAM and pneumothorax
*'''Sirolimus note:''' sirolimus impairs wound healing and may need to be withheld during active air leak management — discuss with the patient's pulmonologist<ref name="LAMFound"/>

'''2. Chylous effusion:'''
*'''Thoracentesis''' for symptomatic chylothorax — send fluid for triglycerides, cell count, LDH, protein, cultures
*Chylous effusions respond well to '''sirolimus''' (first-line medical treatment rather than invasive procedures)<ref name="LAMFound"/>
*Avoid repeated thoracentesis when possible (nutritional depletion from chyle loss; consider dietary modification with medium-chain triglycerides)
*Pleurodesis or thoracic duct ligation for refractory cases

'''3. Renal AML hemorrhage:'''
*Acute retroperitoneal hemorrhage from ruptured AML: '''hemodynamic resuscitation''', emergent CT angiography, '''selective arterial embolization''' is preferred over nephrectomy (nephron-sparing approach)<ref name="ERS2010"/>
*AML >4 cm: higher hemorrhage risk; elective embolization or mTOR inhibitor therapy to shrink tumor

'''4. Respiratory support:'''
*Supplemental O2 to maintain SpO2 ≥90%<ref name="LAMFound"/>
*Bronchodilators (albuterol) — may benefit the ~20–25% with reversible airway obstruction; reasonable to trial in any symptomatic LAM patient<ref name="LAMFound"/>
*Non-invasive ventilation or intubation for respiratory failure

'''5. Disease-modifying therapy (outpatient — coordinate with pulmonology):'''
*'''Sirolimus (rapamycin)''' — '''the only FDA-approved treatment''' for LAM; mTORC1 inhibitor<ref name="MILES"/>
**MILES trial: stabilized FEV1 decline (placebo lost 12 mL/month vs. sirolimus gained 1 mL/month; p<0.001); reduced serum VEGF-D; improved quality of life<ref name="MILES"/>
**Treatment is '''suppressive, not curative''' — long-term continuous therapy required; disease progresses again upon discontinuation<ref name="LAMFound"/>
**Sirolimus also reduces pneumothorax recurrence by ~80% and is first-line for chylous effusions and AML<ref name="SirolimusPTX">Cheng C, et al. Sirolimus reduces the risk of pneumothorax recurrence in patients with LAM. ''Orphanet J Rare Dis''. 2022;17(1):257.</ref>
**Indications: FEV1 <70% predicted, FEV1 decline ≥90 mL/year, refractory chylous effusions, AML ≥4 cm, significant disease burden<ref name="LAMFound"/>
**Side effects: oral mucositis (most common), hyperlipidemia, diarrhea, peripheral edema, delayed wound healing, increased infection risk, ovarian cysts
*'''Everolimus:''' Alternative mTOR inhibitor; FDA-approved for TSC-associated AML and subependymal giant cell astrocytoma; similar efficacy and side effect profile
*'''Avoid estrogen-containing medications:''' oral contraceptive pills, hormone replacement therapy — may accelerate disease<ref name="StatPearls"/>
*Lung transplantation for end-stage disease (FEV1 <30% predicted or severe functional limitation); note: LAM can recur in transplanted lung<ref name="StatPearls"/>

==Disposition==
*'''Admit:'''
**Pneumothorax requiring chest tube (strongly consider thoracic surgery consultation for pleurodesis discussion given high recurrence rate)
**Significant chylothorax with respiratory compromise
**Acute retroperitoneal hemorrhage from renal AML
**Respiratory failure or new/increased O2 requirement
**Hemodynamic instability
*'''Discharge with close follow-up:'''
**Small, stable pneumothorax managed with observation in a patient with adequate oxygenation and close outpatient follow-up assured
**Known LAM patient with mild exacerbation of dyspnea at baseline, stable vitals, and no evidence of pneumothorax or effusion
**'''Suspected new LAM diagnosis''' (young woman with characteristic CT findings): ensure urgent outpatient pulmonology referral (ideally to a center with LAM expertise)
*'''Discharge counseling:'''
**Return immediately for sudden chest pain, worsening dyspnea, or hemoptysis (pneumothorax recurrence)
**Avoid estrogen-containing contraceptives and hormone replacement
**'''Air travel:''' associated with increased pneumothorax risk — discuss with pulmonologist before flying<ref name="ERS2010"/>
**'''Pregnancy:''' may accelerate LAM progression; requires pre-pregnancy counseling with a LAM specialist<ref name="StatPearls"/>
**Scuba diving is '''contraindicated''' (pneumothorax risk)
**Do not discontinue sirolimus without discussing with pulmonologist
**The LAM Foundation (www.thelamfoundation.org) is an excellent patient resource

==See Also==
*[[Pneumothorax]]

*[[Asthma]]
*[[Idiopathic pulmonary fibrosis]]

==External Links==
*[https://www.ncbi.nlm.nih.gov/books/NBK534231/ Lymphangioleiomyomatosis — StatPearls]
*[https://www.thelamfoundation.org/ The LAM Foundation]
*[https://www.atsjournals.org/doi/10.1164/rccm.201709-1965ST ATS/JRS Clinical Practice Guideline: LAM Diagnosis and Management (2017)]
*[https://publications.ersnet.org/content/erj/35/1/14 ERS Guidelines for Diagnosis and Management of LAM (2010)]
*[https://www.nejm.org/doi/full/10.1056/NEJMoa1100391 MILES Trial — Sirolimus in LAM (NEJM 2011)]
*[https://my.clevelandclinic.org/health/diseases/16022-lymphangioleiomyomatosis-lam LAM — Cleveland Clinic]

==References==
<references/>

[[Category:Pulmonary]]
[[Category:Heme/Onc]]

Lymphangioleiomyomatosis - Revision history

Danbot: Strip excess bold

Danbot: Moved intro into Background as bullets; removed excessive bold from bullet lead-ins; added Pulmonary fibrosis differential and SOB DDX templates