The nails represent functionally and aesthetically very important cutaneous appendages. Although often seen as the little brother of hair and being of lesser importance life without nails is much harder than without hair. Wigs are available in all sizes and colours at virtually all prices but nothing similar can be bought even for a lot of money. Hair can be hidden under a hat or scarf but the hands and fingers and their nails are virtually always visible.
The nail starts developing with the formation of the limbs at the 8th to 9th week of gestation. Its development depends on the concerted action of many growth and signalling factors, and only one lacking or one false signal will make normal nail development impossible. Much research has concentrated on hair and it turned out that nail development is even more complex. It is not surprising that so many ectodermal dysplasia syndromes are associated with nail deformations.
Recent research has shown the close and intimate reltionship of the musculo-skeletal system with the nail unit. Some rheumatologists now call the nail a musculo-skeletal appendage and explain part of the psoriatic nail changes with their close anatomic relationship with the bone and joint of the distal phalanx refuting the long-held anticipation of the nail changes as being immuno-mediated.
As a cutaneous appendage, the nail apparatus may react with the skin and demonstrate a number of nail changes, many of which are specific allowing the correct diagnosis to be made, but even more are less or non-specific and have to be seen with the corresponding dermatosis. When no accompanying skin lesions are present a correct diagnosis is even more difficult to reach and often requires a biopsy and expert histopathological diagnosis. This touches another difficult area: nail surgery.
Nail surgery is an integral part of dermatologic surgery. Although many patients primarily consult surgeons because „they can do everything“ even plastic and hand surgeons usually have only rudimentary knowledge of the nail’s biology, physiology, growth pattern, normal and pathologic anatomy and histopathology. Therefore, their foremost diagnostic-therapeutic approach is often nail avulsion, which by itself is almost never a treatment. It is self-evident that nail surgery requires in-depth knowledge of all aspects of the nail and it is the dermatologist who takes time and all efforts to learn this. Unfortunately, the huge number of mal-treated ingrown toenails with permanent mutilation of the bit toe gives strong evidence that this situation has not really changed to the better. And here we are at another important issue: function and aesthetics.
Finger and toe nails have important functions for the protection of the distal phalanx, which in turn is a very important sensory organ, a most versatile tool and a weapon for defence and to scratch. For the great toe, the nail exerts counter-pressure for the soft tissue of the toe tip and thus prevents it from being heaped up and dorsally disclocated; thus the big toenail even adds to the safety of gait. Malformed finger nails are embarrassing and may cause considerable concern. In our world of youth and well-being, healthy good-looking nails are important features.
Finally, the nails may reflect general health as was already mentioned by Hipokrates more then 2000 years ago when he noted that clubbed fingers were associated with serious pulmonary and heart problems.
An up-to-date nail book in Chinese is overdue. The authors are reputed experts in this field that unfortunately was a bit neglected for many years. I hope that this book will be a great success in all respects.