As with all of medicine, correct therapy depends on a correct diagnosis, which is established through clinical and laboratory (see chapter on techniques in diagnosing manifestations of infections) observations.

The progress of an infection can be more carefully monitored in the skin than in any other organ due to ease of clinical observation. The four primary signs of acute infection are color, warmth, tenderness (and/or pain) and swelling. Additional signs include induration, erosion or ulceration, vesiculation, pustulation, linear streaking along lymphatics, lymphadenopathy, asymmetry, vasculitic appearance, necrosis, and progression. This progression can be visually monitored and marking the edge with an indelible marker can help demonstrate the spread or regression of the edge of the infection. These clinical signs can all be less apparent in the growing population of immunocompromised patients who do not mount the typical immune response. On the contrary, immunocompromised patients may have worse clinical signs that appear at a faster rate than those seen in nonimmunocompromised individuals.

Probably the best example of the importance of these principles in all of medicine is illustrated in the case of necrotizing fasciitis, the sine qua non of importance for the skin and infectious diseases. Each chapter will have a brief history about the disease or diseases covered at the beginning as well as a reminder of potential pitfalls and myths at the end. The pitfalls and myths section will help to serve as a summary of where it is easy to go wrong clinically and where you want to go right. Necrotizing fasciitis will be used as a brief sample of how each chapter will be laid out in the book.