FLCN and cystic disease of lung: This case presents a young female presenting with only cystic lung disease and kidney tumors, identified as having a never before identified heterozygous mutation in the folliculin (<i>FLCN</i>) gene which is the likely cause of her syndrome.<h4>Case presentation</h4>A 34-year-old female was found to have bilateral renal masses, 2.4 cm on the right and 7.6 cm on the left, as well as multiple, small cysts in the lungs.