Ferdinand-Jean Darier was the biggest of the big names in French Dermatology, having headed the Department of Derm at Hôpital St-Louis in the early 1900's. His name is everywhere at St-Louis, and he is widely regarded as the father of modern dermatology in the Francophone world, and certainly one of the giants who made our specialty what it is today. His expertise resided in his ability to observe and describe syndromes and patterns,which in turn led to disease descriptions. Darier's disease bears his name, but he also described such widely disparate conditions as DFSP, sarcoidosis and erythema annulare centrifugum. And, of course, the eponymous Darier's sign of urticaria pigmentosa, which would happen if we rubbed these brown spots pictured here. Also, he headed the Department when Sabouraud (of Sab-Dex fame), Brocq, Fournier (abscess) and Besnier were hanging around at St-Louis. They were the New York Yankees of dermatology, the Big Five, as it were. The Big Five (Le Grand Cinq) did not include Baron Dupuytren, another famous French docteur who was universally reviled as "first among surgeons, last among men", which happens to be my favorite insult of all time. He was at Hôtel Dieu.
I gave you credit if you named the sign or the condition.