Ash Leaf Macule of Tuberous Sclerosis
There are a few cutaneous signs of internal disease which should be automatically answered, as automatically as Pavlov's dogs would salivate or Rush Limbaugh would say "liberals". The ash leaf is one of those signs. Named for the elongated depigmented macule that in many cases resembles the leaf of an ash tree, it is highly suggestive of Tuberous Sclerosis. It is part of that mysterious genetic mechanism which causes all the manifestations of TS, including the hamartomas, angiofibromas (adenoma sebaceum) periungual fibromas, shagreen patches, cortical tumors, angioleiomyomas in the kidneys, as well as retinal phakomas.
There is a list of major and minor characteristics of TS which are used for diagnosis of TS, and are well worth reviewing on the Mayo Clinic website, or any one of a number of TS-related sites.
Most of you smoked this answer like a cheap cigar, and so take a bow. It was not a particularly easy question.
I am in mourning over the end of the Tour de France, so to make me feel better, and to get yourselves a bonus point, how many turns are there on the climb up Alpe d'Huez?
p.s. Saw a patient who had been to four (I think) dermatologists for evaluation of "rosacea", but when she came to us, had alopetic eyebrows, an infiltrated face with swelling above the eyebrows, on her ears and to a lesser degree on her chin and cheeks. It was a pretty classic presentation of leonine facies, and we biopsied her and asked them to rule certain things out. For two additional, non-Tour de France related bonus points, name two ddxs for leonine facies.