It is only fitting to preface the fourth edition of Dermatology Secrets Plus with a quote from the great Athenian philosopher Socrates, since the entire Secrets series of medical textbooks is based on the Socratic method of teaching, which involves asking and answering questions to stimulate critical thinking. The Socratic method (elenchus) in medicine is primarily taught on medical rounds or even at the patient’s bedside and has been used for centuries to challenge the minds of medical trainees. It is the goal of this textbook to simulate the kinds of questions that might be used on dermatology patient rounds as the senior attending physician applies the Socratic method of teaching to medical students, interns, and residents. The fourth edition once again finds me working with my friend and colleague, Dr. Joseph Morelli, a renowned pediatric dermatologist, who continues to bring his outstanding insight, hard work, and expertise to this book. This edition brings many changes—every chapter has been revised with the addition of numerous new questions and tables. We have paid particular attention to the length of the answers to questions, believing that more concise answers will enhance the reader’s learning. Since dermatology is a largely visual medical specialty, we have also added 99 new or replacement clinical color photographs to tie the questions to a visual experience. Many of the new photographs have come from the JLA Collection, which was donated to the University of Colorado by Dr. John L. Aeling, a former editor of this book; the WLW Collection, donated to the University of Colorado by Dr. William L. Weston, the former chairman of the Department of Dermatology at the University of Colorado; and the JB Collection, donated to the University of Colorado by Dr. Joanna Burch, who is currently one of our pediatric dermatologists. Finally, we have added a much needed new chapter, “Disorders of the Female Genitalia.”