I commend the authors on a job well done. I appreciate the time and effort required by them to produce a text and for sharing their knowledge. Overall, the text is well written and easy to understand. The most important feature of any pathology atlas is the inclusion of clear photomicrographs corresponding to key points in the text, and this was certainly accomplished.

I purchased the first edition of the book as a pathology resident when I became interested in dermatopathology. I knew I would need to learn more about the diagnosis of alopecia, which has a reputation of being a more challenging part of the field. I was unsure what the anxiety was about when such a small atlas arrived and was so clearly written. After I read through the text, I felt that diagnosing alopecia would be easy and each biopsy would demonstrate the descriptions found in my new text.

As my training progressed, I was fortunate to attend alopecia clinics in the dermatology department and see the corresponding biopsies during residency and in fellowship. Usually, the biopsies were expertly performed, grossed, and diagnosed, again, making the process seem exciting and deceptively easy. In reviewing outside consultations, however, I also quickly learned that many cases would not be easily diagnosed.

I entered private practice where I, again, have been fortunate enough to work with excellent clinicians and supported by helpful and experienced colleagues. I was lucky, in a way, when a majority of my first alopecia biopsies were to confirm central centrifugal cicatricial alopecia, and the biopsies usually corresponded to that diagnosis. Rarely, a biopsy would arrive either without clinical information, an inadequate amount of tissue, or as a consultation on poorly oriented tissue, etc. I realized how frustrating it was for everyone involved when a specific diagnosis could not be rendered and especially for the patient for having to endure the pain of scalp biopsies. When a challenging case of alopecia presents itself, I always turn to my text and enjoy the brief, yet sufficient information.

When I realized there was a second edition of my trusty alopecia text, I was both excited and a bit nervous. I have read the first edition several times, both continuously and intermittently. I liked that the first edition was succinct, and having nearly memorized some portions, I felt I had conquered many of the topics. I found it easy to get through the information without having to sift through volumes of unnecessary information. I tried not to panic as I opened the new edition.

My first observation is that the book is a different in color and a bit thicker, while still a convenient size for handling and carrying around. I find some comfort in not having to refer to a large text for alopecia—I can at least easily handle the book when faced with the frustration of making a less than specific diagnosis based on the occasional biopsy without clinical information or with inadequate tissue.

Of course, I am a fan of the first edition, but I was sometimes wishing for more photomicrographs to correspond to the descriptions in the text. I was also hopeful that there might be a few algorithms in the second edition. My review will thus be a comparison of the first and second editions.

The second edition includes a new first chapter, which is a guide to using the book. Like a pep-rally for the weary or novice, the authors give the reader a title of "trichopathologist" and outline how following the text will lead easily to the correct diagnosis.

The chapter of "Normal hair anatomy and architecture" is similar to the first edition, with some improvement in the clarity of photos and labeling of the structures. A few additional photos are included, as well. This is a trend throughout the book and a definite improvement.

The authors have maintained the chapter titled "Distinctive or critical histological features and associated diseases" and have retained the lists of diseases with certain characteristics. I find this chapter quite useful; though not an algorithm, the lists help to narrow down the diagnosis. Likewise, the "Clinical correlation" chapter and clinical photos throughout the book are critical, especially when faced with a histological diagnosis that is incongruous with the clinical impression.

The core of the text consists of the chapters addressing specific diagnoses. While retaining all the previous chapters, the authors have included several new chapters, including: Psoriatic alopecia, Tumor-necrosis factor-alpha inhibitor associated psoriasiform alopecia, Folliculitis decalvans, Fibrosing alopecia in a pattern distribution, Erosive pustular dermatosis, Trichodysplasia of immunosuppression, and Chemotherapy induced alopecia.

I find myself leaning toward the "lumper" side of dermatopathology and am wary of too many "distinct" entities placed easily in a single category. Specifically, I do not see the need for three different chapters addressing lichen planopilaris (Lichen planopilaris, Frontal fibrosing alopecia, and Fibrosing alopecia in a pattern distribution), when the reader could be presented the different clinical patterns in a single chapter, and perhaps in a table format with distinguishing characteristics. Likewise, Folliculitis decalvans was included in the Central centrifugal cicatricial alopecia chapter in the first edition. However, the authors dedicated a separate chapter to the condition in the second edition, although they do consider it a clinical pattern of central centrifugal cicatricial alopecia.

Additionally, I am thrilled to have been reminded of "erosive pustular dermatosis" and can suggest the diagnosis in the proper clinical setting. However, I am not sure that it is correctly included in the book of hair pathology and might be better placed in a chapter covering other findings from scalp biopsies for alopecia, such as alopecia neoplastica, angiosarcoma, seborrheic dermatitis, etc. should the authors feel the need for such a chapter.

I also noticed that the authors now include descriptions of a few therapeutic options for several entities. While the authors do not overwhelm the text with this information, the inclusion of this information places the text in danger of seeming antiquated, should better treatments emerge in the future. Of course, this might warrant a third edition.

The new chapters addressing psoriatic alopecia and TNF-alpha inhibitor associated psoriatic alopecia are helpful and point out the importance of the location of eosinophils and plasma cells to distinguish the two (deeper in drug induced alopecia). The text also highlights important points that psoriatic alopecia can have eosinophils and is often treated before biopsy making epidermal changes unnecessary for the diagnosis. Another important point made is that alopecia areata often presents without peribulbar inflammation. There are many useful points throughout the text that readers are certain to discover for themselves.

Fortunately, the authors retained the summaries of each condition at the end of each chapter, and even expanded the information provided. Several of the summaries at the ends of the chapters for specific entities now include a list of "pitfalls" which is incredibly helpful and alone is a reason to purchase the new edition. I will check these before rendering a diagnosis regularly until I have these potential pitfalls committed to memory.

Suggestions for the next edition, should there ever be one, include a series of photos or drawings showing the phases of the hair cycle in sequence in the normal hair anatomy chapter. This seems to be a confusing concept that could be easily illustrated. I would love to have a series of algorithms, although they might be difficult to generate, as several entities share so many characteristics.

Overall, I recommend adding the new edition to the collection of anyone diagnosing alopecia, including dermatologists, dermatopathologists, and residents. Dermatologists will benefit from owning this book, as it has wonderful clinical photos, and can be helpful when the histopathology does not 'fit" the clinical impression, especially, the summary boxes addressing differential diagnoses and pitfalls. The book is relatively inexpensive, especially considering the number of color photomicrographs it contains, as well as the invaluable text.

In summary, when compared to the first edition, the second edition contains new chapters covering: Psoriatic alopecia, Tumor-necrosis factor-alpha inhibitor associated psoriasiform alopecia, Folliculitis decalvans, Fibrosing alopecia in a pattern distribution, Erosive pustular dermatosis, Trichodysplasia of immunosuppression, and Chemotherapy induced alopecia. The second edition also includes a brief description of treatments for several entities. Most importantly, the new edition contains many additional photos, with better clarity, and the summaries at the ends of the chapters now include potential pitfalls to avoid.