Emerging biomarkers of lymphangioleiomyomatosis.

INTRODUCTION: Lymphangioleiomyomatosis (LAM) is a destructive lung disease affecting primarily women. LAM is caused by inactivating mutations in the tuberous sclerosis complex (TSC) genes, resulting in hyperactivation of mechanistic/mammalian target of rapamycin complex 1 (mTORC1). Over the past five years, there have been remarkable advances in the diagnosis and therapy of LAM, including the identification of vascular endothelial growth factor D (VEGF-D) as a diagnostic biomarker and the US Food and Drug Administration approval of sirolimus as therapy for LAM. In appropriate clinical situations VEGF-D testing can make lung biopsy unnecessary to diagnose LAM. However, there remains an urgent unmet need for additional biomarkers of disease activity and/or response to therapy. Areas covered: This work reviews VEGF-D, an established LAM biomarker, and discusses emerging biomarkers, including circulating LAM cells, imaging, lipid, and metabolite biomarkers, focusing on those with the highest potential impact for LAM patients. Expert commentary: Ongoing research priorities include the development of validated biomarkers to 1) noninvasively diagnose LAM in women whose VEGF-D levels are not diagnostic, 2) accurately predict the likelihood of disease progression and 3) quantitatively measure disease activity and LAM cell burden. These biomarkers would enable personalized, precision clinical care and fast-track clinical trial implementation, with high clinical impact.