Fatigue, Muscular Performance, and Quadriceps Fiber Type Profile in Lymphangioleiomyomatosis and Healthy Matched Controls.

PURPOSE: Fatigue is a common symptom in lymphangioleiomyomatosis (LAM) and is associated with reduced physical activity and quality of life. Coexistent skeletal muscle dysfunction has been reported for other chronic lung diseases but has not been investigated in LAM.

METHODS

Fifteen patients with LAM and 15 matched individuals without LAM (NL) underwent computerized lower extremity dynamometry, standardized functional tests, and fatigue surveys. Immunohistochemistry to detect LAM+ cells and to characterize fiber-type distribution was performed on vastus lateralis (VL) samples of LAM and NL. Maximal cardiopulmonary exercise test (CPET) and six-minute walk test (6MWT) were additionally conducted for LAM. Welch's t-testing compared measures between LAM and NL. Pearson correlation tested relationships between variables. Data are mean ± SD.

RESULTS

LAM exhibited lower (p < 0.05) muscular force (by 220 ± 89 N), power (by 312 ± 129 W), and endurance (by 4674 ± 1974 N*sec) in dynamometry and functional tests (by 119 ± 45s in wall squat test), and worse fatigue survey scores (p = 0.02 to 0.0004). Poorer muscular endurance in LAM was associated with less distance achieved in 6MWT (r = 0.68), lower VO2max (r = 0.58), and worse fatigue (r = 0.56). LAM with worse fatigue also exhibited lower relative fat utilization in CPET (r = 0.75, p = 0.005). No LAM+ cells were detected in VL samples, nor between-group differences in fiber type distribution.

CONCLUSION

Muscular endurance and strength is lower in LAM, coincident with greater self-reported fatigue. Fiber type shift reported for skeletal muscle in other chronic lung disease is not observed in LAM. Further work is needed to elucidate peripheral muscle mechanisms for fatigue and exercise intolerance in LAM.