SAT-651 Ethnic Differences in the Relationship Between Uric Acid Clearance and Insulin Sensitivity

Background: Hyperuricemia is associated with gout, type-2 diabetes, hypertriglyceridemia, and other insulin resistant (IR) states. Impaired clearance of uric acid (UA) has been proposed to play a role in hyperuricemia in IR. In a small study, urinary UA clearance was negatively associated with IR. African-Americans (AA) are more insulin resistant than Caucasians (CA). However, plasma UA levels are lower in AA. Ethnic differences underlying the relationship between UA clearance and insulin sensitivity (Si) remain unknown.

Objective: To compare the relationships between UA production, clearance, and Si in AA and CA.

Design: In a cross-sectional study, AA (n = 40; age 43 ± 10 years; BMI 41.3 ± 9.7 kg/m2) and CA (n = 88; age 44 ± 13 years; BMI 32.9 ± 8.2 kg/m2) subjects underwent an intravenous glucose tolerance test (IVGTT) to derive Si using the Minimal Model. Plasma UA and creatinine (Cr), were measured in the NIH Department of Laboratory Medicine. Urinary UA and Cr levels in spot urine samples were measured using a colorimetric assay. Fractional Excretion (FE) of UA and urine urate-to-creatinine ratio (UUCR), a measure of uric acid production, were calculated.

Results: AA had a significantly higher BMI (p < 0.0001), percent body fat (45.8 ± 8.9 vs. 39.7 ± 11.5 %, p = 0.0007), A1C (5.8 ± 0.4 vs. 5.5 ± 0.3 %, p = 0.0006), diastolic BP (74 ± 9 vs. 71 ± 8 mm of Hg, p = 0.02), and lower Si (2.36 ± 2.7 vs. 4.43 ± 3.4 min−1·μU·ml−1, p = 0.0004) compared to CA. Stepwise multiple regression analysis was performed with independent variables A1c, fasting glucose, fasting insulin, triglycerides, and Si. Among these, Si was a significant predictor of FE of UA in CA (r = 0.33, p=0.001), but not AA (r = - 0.02, p=0.92).There was also a negative association between Si and plasma UA in CA (r = 0.48, p < 0.0001), but not in AA (r = 0.06, p = 0.70). There was no association between Si and UA production in both groups (AA: p = 0.33, CA: p = 0.69).

Conclusion: These findings suggest that reduced insulin sensitivity may not play a major role in the pathogenesis of hyperuricemia in AA in insulin-resistant states.

SAT-624 Predictive Ability of Lipoprotein Insulin Resistance (LPIR) Score in South Asians: A Comparison of Surrogate Indices of Insulin Sensitivity/Resistance

South Asians (SA) are at higher risk for developing insulin resistance (IR) and type 2 diabetes. Consequently, identifying IR in this population is important. Lack of standardization and harmonization of insulin assays limit the clinical use of insulin-based surrogate indexes of insulin resistance. The lipoprotein insulin resistance (LPIR) score, a metabolomic marker, reflects the lipoprotein abnormalities observed in insulin-resistant states. The reliability of the LPIR score to predict IR in South Asians is currently unknown. In this study, we aimed to evaluate the predictive accuracy of LPIR compared to other fasting-based surrogate indices in SA.

In a cross-sectional study of 59 non-diabetic SA subjects (age 36 ± 8 years, BMI 26.5 ± 5.2 kg/m²), we used calibration model analysis to assess the ability of the LPIR score and other simple surrogate indices [homeostasis model assessment (HOMA-IR), quantitative insulin sensitivity check index (QUICKI) and Adipose tissue insulin sensitivity (Adipo-SI)] to predict insulin sensitivity derived from the reference frequently sampled intravenous glucose tolerance test (FSIVGTT) and Minimal Model analysis (SiMM). LPIR scores were calculated using six lipoprotein particle concentrations and sizes measured by nuclear magnetic resonance (NMR) spectroscopy. Further, quantitative predictive accuracy and index comparisons were determined by root mean squared error (RMSE) of prediction and leave-one-out cross-validation-type RMSE of prediction (CVPE). Receiver operating characteristic (ROC) curve analysis was performed to determine how well LPIR distinguished insulin resistant individuals, categorized as an SiMM < 3.

As determined by calibration model analysis, Adipo-SI, HOMA-IR, and QUICKI showed moderate correlations with for SiMM (Adipo-SI: r = 0.66; HOMA-IR: r = 0.60; QUICKI: r = 0.57, p = <0.0001). No significant differences were noted among CVPE or RMSE from any of the routinely used surrogate indices when compared with LPIR. The ROC area under the curve was 0.76 (95% CI 0.64–0.87) suggesting that LPIR performed well in identifying insulin resistant subjects. The optimal cut-off in IR individuals was LPIR >46 (sensitivity: 75.9 %, specificity: 70.0%). We conclude that NMR-derived LPIR may be an appropriate index to assess insulin resistance in South Asians.

OR08-05 Sex and Ethnic Differences in Advanced Lipoprotein Profiles in South Asians, African-Americans, and Caucasians

Background: African-Americans (AA) and South Asians (SA) are known to have higher risk for T2D and cardiovascular disease (CVD) compared to Caucasians (CA). Advanced analysis of lipoprotein particles with nuclear magnetic resonance (NMR) spectroscopy can offer insights into CVD risk and lipid metabolism beyond a standard lipid panel. Insulin resistance (IR) is known to be associated with atherogenic lipoprotein profile.

Objective: To characterize the lipoprotein profile in AA, CA, and SA men and women.

Design: A cross-sectional study of 182 healthy, non-diabetic SA, AA and CA patients was conducted at NIH. Subjects underwent an intravenous glucose tolerance test from which insulin sensitivity (Si) was derived using the Minimal Model. Lipoprotein profiles were measured by NMR with the LP4 deconvolution algorithm, which reports triglyceride-rich lipoprotein particles (TRLPs), high-density lipoprotein particles (HDLPs), and low-density lipoprotein particles (LDLPs). For group comparisons, Si was adjusted for age and fat free mass. Lipoprotein parameters were adjusted for age and body fat %.

Results: Fifty-nine non-diabetic SA (33 males, 26 females), 49 AA (26 males, 23 females), and 74 CA (29 males, 45 females) were included in the study. Ethnic differences in Si were observed in men (p=0.002) but not in women (p=0.43). SA men had a significantly lower Si than both AA and CA men (p=0.02). TG concentrations and TRL particle number were significantly higher in CA men and women when compared with AA. TRLP size was not different between the ethnic groups in either sex. LDL particle number and ApoB concentration was significantly higher in SA men and women compared to AA and CA. There were no ethnic or sex differences in LDL size. HDL concentration, HDL particle number, and ApoA-I levels were not different between the groups in both sexes. However, in SA, large HDL particle number and HDL particle size was significantly lower than CA. Cholesteryl ester transfer protein (CETP) activity was significantly higher in SA men, but not women, when compared with AA and CA. Ethnic differences in LDLP and L-HDLP number remained even after adjusting for Si.

Conclusions: In SA men and women, the lipoprotein phenotype (higher LDLP and lower L-HDLP) is independent of insulin sensitivity. Increased CETP activity may contribute to the lower large HDL particle number in this group. In AA, TG and TRLP number were lower as previously reported. Further investigation is needed to determine the factors mediating the atherogenic profile in SA.

HMGA2 Moderately Increases Fetal Hemoglobin Expression in Human Adult Erythroblasts

Induction of fetal hemoglobin (HbF) has therapeutic importance for patients with beta-hemoglobin disorders. Previous studies showed that let-7 microRNAs (miRNAs) are highly regulated in erythroid cells during the fetal-to-adult developmental transition, and that targeting let-7 mediated the up-regulation of HbF to greater than 30% of the total globin levels in human adult cultured erythroblasts. HMGA2 is a member of the high-mobility group A family of proteins and a validated target of the let-7 family of miRNAs. Here we investigate whether expression of HMGA2 directly regulates fetal hemoglobin in adult erythroblasts. Let-7 resistant HMGA2 expression was studied after lentiviral transduction of CD34(+) cells. The transgene was regulated by the erythroid-specific gene promoter region of the human SPTA1 gene (HMGA2-OE). HMGA2-OE caused significant increases in gamma-globin mRNA expression and HbF to around 16% of the total hemoglobin levels compared to matched control transductions. Interestingly, no significant changes in KLF1, SOX6, GATA1, ZBTB7A and BCL11A mRNA levels were observed. Overall, our data suggest that expression of HMGA2, a downstream target of let-7 miRNAs, causes moderately increased gamma-globin gene and protein expression in adult human erythroblasts.

Erythroid-Specific Expression of LIN28A Is Sufficient for Robust Gamma-Globin Gene and Protein Expression in Adult Erythroblasts

Increasing fetal hemoglobin (HbF) levels in adult humans remains an active area in hematologic research. Here we explored erythroid-specific LIN28A expression for its effect in regulating gamma-globin gene expression and HbF levels in cultured adult erythroblasts. For this purpose, lentiviral transduction vectors were produced with LIN28A expression driven by erythroid-specific gene promoter regions of the human KLF1 or SPTA1 genes. Transgene expression of LIN28A with a linked puromycin resistance marker was restricted to the erythroid lineage as demonstrated by selective survival of erythroid colonies (greater than 95% of all colonies). Erythroblast LIN28A over-expression (LIN28A-OE) did not significantly affect proliferation or inhibit differentiation. Greater than 70% suppression of total let-7 microRNA levels was confirmed in LIN28A-OE cells. Increases in gamma-globin mRNA and protein expression with HbF levels reaching 30-40% were achieved. These data suggest that erythroblast targeting of LIN28A expression is sufficient for increasing fetal hemoglobin expression in adult human erythroblasts.

Ask about ice, then consider iron

BACKGROUND AND PURPOSE

The study aims to review a condition defined by the desire to consume ice in order to satisfy an addictive-like compulsion, rather than for purposes of hydration or pain relief. This condition is called ice pica, or pagophagia. Associations between ice pica and iron deficiency, suggestions for clinical screening of at risk populations, and recommendations for treatment and follow-up care are provided.

DATA SOURCES

An extensive literature review of original research articles, reviews, clinical practice manuscripts, and scientific publications on pica and pagophagia.

CONCLUSIONS

A compulsion or craving for the consumption of ice is often overlooked in clinical practice. It is therefore important for clinicians to include ice pica as part of the review of systems for certain patient populations. Ice pica is frequently associated with iron deficiency, and iron supplementation is an effective therapy in most cases.

IMPLICATIONS FOR PRACTICE

Knowledge gained from screening for ice pica can generate valuable patient information and lead to the diagnosis and treatment of iron deficiency. The populations at risk include young women and blood donors of either sex.

Iron dose-dependent differentiation and enucleation of human erythroblasts in serum-free medium

Improvements in ex vivo generation of enucleated red blood cells are being sought for erythroid biology research, toward the ultimate goal of erythrocyte engineering for clinical use. Based upon the high levels of iron-saturated transferrin in plasma serum, it was hypothesized that terminal differentiation in serum-free media may be highly dependent on the concentration of iron. Here adult human CD34(+) cells were cultured in a serum-free medium containing dosed levels of iron-saturated transferrin (holo-Tf, 0.1-1.0 mg/ml). Iron in the culture medium was reduced, but not depleted, with erythroblast differentiation into haemoglobinized cells. At the lowest holo-Tf dose (0.1 mg/ml), terminal differentiation was significantly reduced and the majority of the cells underwent apoptotic death. Cell survival, differentiation and enucleation were enhanced as the holo-Tf dose increased. These data suggest that adequate holo-Tf dosing is critical for terminal differentiation and enucleation of human erythroblasts generated ex vivo in serum-free culture conditions. Published 2013. This article is a US Government work and is in the public domain in the USA.

Prevalence of uterine leiomyomas in lymphangioleiomyomatosis

OBJECTIVE

To determine the frequency of uterine leiomyomas and hysterectomy in patients with lymphangioleiomyomatosis (LAM), a disease characterized by proliferation of abnormal-appearing smooth muscle-like cells.

DESIGN

Retrospective study.

SETTING

Natural history study at the National Institutes of Health.

PATIENT(S)

456 patients with sporadic LAM and LAM associated with tuberous sclerosis complex (LAM/TSC).

INTERVENTION(S)

Review of records and pelvic computed axial tomography scans.

MAIN OUTCOME MEASURE(S)

Prevalence of uterine leiomyomas and hysterectomy.

RESULT(S)

A total of 174 women had uterine leiomyomas (38%). One hundred eighteen were diagnosed by computed tomographic scan and 56 were diagnosed by hysterectomy. Among 323 patients who did not have hysterectomy, 105 of 270 patients (39%) with sporadic LAM and 13 of 53 (25%) with LAM/TSC had uterine leiomyomas. Hysterectomy was performed in 108 of 378 subjects with sporadic LAM and 25 of 78 with LAM/TSC. Fifty-six patients were found to have uterine fibroids on hysterectomy. The most common indications for hysterectomy were uterine leiomyoma, LAM, and endometriosis.

CONCLUSION(S)

Uterine leiomyomas are not more common in LAM than in the general population. However, in LAM, the frequency of hysterectomy is higher because of it having been recommended for treatment of LAM.

CT of sclerotic bone lesions: imaging features differentiating tuberous sclerosis complex with lymphangioleiomyomatosis from sporadic lymphangioleiomymatosis

PURPOSE

To determine if sclerotic bone lesions evident at body computed tomography (CT) are of value as a diagnostic criterion of tuberous sclerosis complex (TSC) and in the differentiation of TSC with lymphangioleiomyomatosis (LAM) from sporadic LAM.

MATERIALS AND METHODS

Informed consent was signed by all patients in this HIPAA-compliant study approved by the institutional review board. Retrospective analysis was performed of the body CT studies of 472 patients: 365 with sporadic LAM, 82 with TSC/LAM, and 25 with TSC. The images were reviewed by using a picture archiving and communication system workstation with bone settings (window width, 1500 HU; window level, 300 HU) and fit-to-screen option. CT image characteristics assessed included shape, size, and distribution of sclerotic bone lesions with subsequent calculation of differences in the frequency of these lesions.

RESULTS

Most commonly the sclerotic bone lesions were round, measured 0.3 cm (range, 0.2-3.2), and were distributed throughout the spine. The frequencies differed among the three patient groups Four or more sclerotic bone lesions were detected in all 25 (100%) of those with TSC, with a sensitivity of .89 (72 of 82) and specificity of .97 (355 of 367) in the differentiation of sporadic LAM from TSC/LAM (P < .01).

CONCLUSION

The number of sclerotic bone lesions at body CT is of potential value in the diagnosis of TSC and in the differentiation of patients with sporadic LAM from those with TSC/LAM. (c) RSNA, 2010.

Expression of growth differentiation factor 15 is not elevated in individuals with iron deficiency secondary to volunteer blood donation

BACKGROUND

Low serum hepcidin levels provide a physiologic response to iron demand in patients with iron deficiency (ID). Based on a discovery of suppressed hepcidin expression by a cytokine named growth differentiation factor 15 (GDF15), it was hypothesized that GDF15 may suppress hepcidin expression in humans with ID due to blood loss.

STUDY DESIGN AND METHODS

To test this hypothesis, GDF15 and hepcidin levels were measured in peripheral blood from subjects with iron-deficient erythropoiesis before and after iron supplementation.

RESULTS

Iron variables and hepcidin levels were significantly suppressed in iron-deficient blood donors compared to healthy volunteers. However, ID was not associated with elevated serum levels of GDF15. Instead, iron-deficient subjects' GDF15 levels were slightly lower than those measured in the control group of subjects (307 +/- 90 and 386 +/- 104 pg/mL, respectively). Additionally, GDF15 levels were not significantly altered by iron repletion.

CONCLUSIONS

ID due to blood loss is not associated with a significant change in serum levels of GDF15.

Reversible airflow obstruction in lymphangioleiomyomatosis

BACKGROUND

We previously reported that approximately one-fourth of patients with lymphangioleiomyomatosis (LAM) may respond to therapy with bronchodilators. However, the validity of those observations has been questioned. The aims of the present study were to determine the prevalence of reversible airflow obstruction in patients with LAM and to identify associated clinical and physiologic parameters.

METHODS

First, the clinical and physiologic characteristics of 235 patients were analyzed to determine the frequency of the response to albuterol during a total of 2,307 visits. Second, we prospectively evaluated the response to albuterol (2.5 mg) and ipratropium (500 mug) in 130 patients, and correlated their responses with their clinical and physiologic characteristics.

RESULTS

In the retrospective study, 51% of the patients responded at least once to bronchodilators; of these, 12% responded >/= 50% of the time. A higher frequency of positive bronchodilator responses was associated with greater rates of decline in FEV(1) and diffusing capacity of the lung for carbon monoxide (Dlco). In the prospective study, 39 patients (30%) responded to bronchodilators, including 12 to ipratropium, 9 to albuterol, and 18 to both. The prevalence of asthma and smoking in the 39 responders was not different from that seen in the 91 nonresponders. Patients who responded to ipratropium, albuterol, or both had significantly (p < 0.02) lower FEV(1) and Dlco, and a greater rate of FEV(1) decline (p = 0.044) and Dlco decline (p = 0.039) than patients who did not respond to these bronchodilators. After adjusting for FEV(1)/FVC ratio, Dlco decline also was greater in responders than in nonresponders (p = 0.009).

CONCLUSIONS

Patients with LAM may have partially reversible airflow obstruction. A positive response to bronchodilators is associated with an accelerated rate of decline in pulmonary function.

Genetic and morphologic determinants of pneumothorax in lymphangioleiomyomatosis

Lymphangioleiomyomatosis, a multisystem disease affecting women, is characterized by proliferation of abnormal smooth muscle-like cells in the lungs, leading to cystic destruction of the parenchyma and recurrent pneumothoraces. Clinical characteristics of lymphangioleiomyomatosis patients were analyzed to determine the relationship of pneumothoraces to disease progression. Patients were genotyped for polymorphisms in genes of extracellular matrix proteins collagen, elastin, and matrix metalloproteinase-1 to assess their association with pneumothoraces. Clinical data and polymorphisms in the genes for types I and III collagen, elastin, and matrix metalloproteinase-1 were compared with the prevalence of pneumothorax. Of 227 patients, 57% reported having had at least one pneumothorax. Cyst size on high-resolution computed tomography scans was associated with pneumothorax; patients with a history of pneumothorax were more likely to have larger cysts than patients who had no pneumothoraces. In patients with mild disease, those with a history of pneumothorax had a faster rate of decline in forced expiratory volume in 1 s (FEV(1); P = 0.001, adjusted for age) than those without. Genotype frequencies differed between patients with and without pneumothorax for polymorphisms in the types I and III collagen and matrix metalloproteinase-1 genes. Larger cysts may predispose lymphangioleiomyomatosis patients to pneumothorax, which, in early stages of disease, correlates with a more rapid rate of decline in FEV(1). Polymorphisms in types I and III collagen and matrix metalloproteinase-1 genes may cause differences in lung extracellular matrix that result in greater susceptibility to pneumothorax.

Sporadic lymphangioleiomyomatosis and tuberous sclerosis complex with lymphangioleiomyomatosis: comparison of CT features

PURPOSE

To retrospectively compare the frequencies of computed tomographic (CT) findings in patients with lymphangioleiomyomatosis (LAM) and patients with tuberous sclerosis complex (TSC) and LAM.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained for the HIPAA-compliant study. In 256 patients with LAM (mean age, 44 years) and 67 patients with TSC/LAM (mean age, 40 years), CT scans of the chest, abdomen, and pelvis were reviewed by a single radiologist. The fraction of lung involvement with cysts was estimated from high-spatial-resolution CT scans. Other findings assessed included noncalcified pulmonary nodules, pleural effusion, thoracic duct dilatation, hepatic and renal angiomyolipomas (AMLs), lymphangioleiomyoma (LALM), ascites, nephrectomy, and renal embolization. Confidence intervals and hypothesis tests of differences in frequencies, comparison of age quartiles, RIDIT analysis, analysis of variance, and correlation coefficients were used in the statistical analysis.

RESULTS

Patients with LAM had more extensive lung involvement (RIDIT score, 0.36) and higher frequency of LALM (29% vs 9%, P<.001), thoracic duct dilatation (4% vs 0, P=.3), pleural effusion (12% vs 6%, P=.2), or ascites (10% vs 6%, P=.3). Patients with TSC/LAM had higher frequency of noncalcified pulmonary nodules (12% vs 1%, P<.01), hepatic (33% vs 2%, P<.001) and renal (93% vs 32%, P<.001) AMLs, nephrectomy (25% vs 7%, P<.001), or renal artery embolization (9% vs 2%, P<.05).

CONCLUSION

The extent of lung disease is greater in LAM than TSC/LAM. Hepatic and renal AMLs and noncalcified lung nodules are more common in TSC/LAM, while lymphatic involvement-thoracic duct dilatation, chylous pleural effusion, ascites, and LALM-is more common in LAM.

CT of pleural abnormalities in lymphangioleiomyomatosis and comparison of pleural findings after different types of pleurodesis

OBJECTIVE

The objective of our article was to describe the spectrum and frequency of pleural abnormalities on CT in patients with lymphangioleiomyomatosis (LAM) and the pleural findings associated with different types of pleurodesis (talc, mechanical, and chemical) performed to treat the complications of pleural disease in these patients.

MATERIALS AND METHODS

Two hundred fifty-eight patients with LAM underwent CT of the chest. Pleural abnormalities assessed included pleural thickening, presence of a pleural mass, areas of high attenuation, effusion, and pneumothorax. In patients who had had pleurodesis, the CT findings were correlated with the type of procedure performed.

RESULTS

One hundred thirty-three (52%) of 258 patients had pleurodesis (unilateral, 68/133; bilateral, 65/133). Pleural abnormalities were more common in patients who had pleurodesis (101/133, 76%) than in those who had not (47/125, 38%) and were more prevalent on the operated side than on the unoperated side of those 68 patients who had unilateral pleurodesis. The frequencies of findings for the group without pleurodesis versus the group with pleurodesis were pleural thickening (26% vs 65%), effusion (10% vs 13%), loculated effusion (2.4% vs 11%), pneumothorax (1.6% vs 10%), areas of high attenuation (1.6% vs 23%), and mass (0.8% vs 14%), respectively. Areas of high attenuation in the pleura were present in all types of pleurodesis (mechanical, 8%; chemical, 13%; talc, 40%) and in two patients who had had repeated thoracentesis or pleurectomy. Pleural masses were present in patients who had had all types of pleurodesis (mechanical, 10%; chemical, 9%; talc, 24%) and in one patient who had had thoracentesis and thoracostomy; the masses commonly enhanced and did not change in size over time.

CONCLUSION

Pleural abnormalities are common in patients with LAM as complications of the disease itself and as sequelae of pleurodesis and other pleura manipulations. Pneumothorax and pleural effusion result from the underlying pathophysiology of LAM, whereas areas of high attenuation and masses develop after all types of pleurodesis and other manipulations of the pleura (i.e., thoracentesis, thoracostomy).

Mikrobiologische Untersuchung zur Ermittlung des Erfolges der Sofortimplantation im parodontal geschädigten Gebiss

AIM

The aim of the present study was to investigate the prevalence of periodontal marker organisms and specific interleukin-1 (IL-1) gene polymorphisms (which show a close association with periodontitis) and their effect on the success of immediate implant placement postextraction in the patient with periodontal disease.

PATIENTS AND METHODS

A group of 59 patients (22 men and 37 women aged 20-81 years, median age 55 years, 18 smokers) with chronic adult periodontitis participated in the study which included a 1-year observation period postoperatively. Prior to tooth extraction two DNA samples were obtained for the microbiological diagnosis of five anaerobic gram-negative pathogens (Haemophilus actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythensis, Prevotella intermedia sensu stricto, Treponema denticola) and to identify the IL-1 gene polymorphisms. Patients were treated with a total of 95 immediate dental implants (26 Ankylos/Friadent and 69 Camlog Root-Line/Camlog Biotechnologies) placed into extraction sites, 78 of which were loaded immediately. After 1 year four failures were observed; all of these patients were smokers.

RESULTS

None of these patients showed a positive IL-1 genotype; periodontal marker organisms were only found in one patient. No significant difference was seen in the microbiological pathogens between smokers and nonsmokers. Of 59 patients, 23 (39%) tested positive for IL-1 genotype polymorphism. Smoking was shown to increase the risk of implant failure. No association was observed between failures and the IL-1 gene polymorphisms or pathogens.

CONCLUSION

In conclusion, our study shows that periodontally infected sites do not seem to be a contraindication for immediate implantation.

Maximal oxygen uptake and severity of disease in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM), a disease that occurs primarily in women, is characterized by cystic lung lesions causing respiratory failure, which may require lung transplantation. Lung diffusion (DLCO) and/or FEV1 are decreased, but frequently not in parallel with each other. Because cardiopulmonary exercise testing (CPET) provides information that is not obtainable from resting cardiopulmonary tests, we performed CPET in 217 LAM patients and correlated exercise data with clinical markers of severity, computed tomography scans, lung function, and histology. VO2max was decreased in 162 patients, of whom 28 did not reach anaerobic threshold; 29 had low oxygen uptake at anaerobic threshold, and 54 developed hypoxemia. Hypoxemia occurred even in patients with near normal DLCO and FEV1. VO2max decreased with an increasing score of histologic LAM severity and was correlated with computed tomography scans, the use of oxygen, and resting PaO2. DLCO and FEV1, however, were the only significant predictors of VO2max. We conclude that CPET uncovers the presence of exercise-induced hypoxemia and assists in grading the severity of disease and determining supplemental oxygen requirements in patients with LAM.