Heterogeneity in the clinical presentation of BHD may contribute to challenges in making this diagnosis. Classic skin findings of BHD include multiple benign follicle hamartomas (fibrofolliculomas and trichodiscomas) on the face, neck, and upper torso. These flesh-colored, dome-shaped papules generally develop in the early 20s, and are highly prevalent in patients with BHD (> 90%). However, they are not required to make the diagnosis, because up to 25% of FLCN mutation carriers have no obvious skin findings. Lung findings, including parenchymal cysts and spontaneous pneumothorax, may provide the earliest clue to the diagnosis. Present in 80% to 90% of patients with BHD, parenchymal cysts are localized in the medial and lower lung zones adjacent to interlobular septa or visceral pleura. The number, appearance, and distribution of these cysts can help distinguish BHD from other cystic lung diseases. For example, in contrast to the lung cysts observed in lymphangiomyomatosis, BHD cysts are frequently fewer, less circular, larger, and less widely distributed. In general, BHD cysts are not associated with functional lung abnormalities. These cysts may come to the attention of chest physicians during evaluation for spontaneous pneumothorax, which occurs in approximately 25% of FLCN mutation carriers. Spontaneous pneumothorax in patients with BHD most commonly occurs in the third or fourth decade, and recurrent pneumothorax is common. Renal malignancies are the most concerning manifestation of BHD and are frequently multiple or bilateral at the time of diagnosis. The prevalence of renal cancers in patients with BHD has been estimated at 27% to 34%, and the mean age at diagnosis is approximately 50 years. In general, these lesions arise much later than the skin or pulmonary manifestations, possibly because of the need for a “second hit” in FLCN.