Skin will often become inflamed and heal at different rates than soft tissues and bone—this helps us a lot when it comes to medical decision-making. In this video, we’ll review the inflammatory processes that affect the skin and soft tissue, how inflammatory markers help us categorize disorders of these areas, and why the textbook organizational systems that you’re used to may be wrong.
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Clinicians encounter inflammation daily and there are lots of inflammatory markers to consider. Which should you order for your patient? Here, you’ll learn the strengths and limitations of each marker, when they’re useful, and when they’re not. We’ll look at laboratory markers of inflammation as well as radiologic and clinical signs so you can take your diagnostic skills to the next level.
Now that we have some of the basics down, let's look at how we can use these concepts in a specific clinical context for skin and soft tissue disorders. Just remember, this lesson is meant to introduce you to how we can use inflammatory markers, and not meant to be a comprehensive course on managing skin and soft tissue disorders. Let's review the basic anatomy of skin and soft tissue. Skin can be thought of in three layers, which are the epidermis, dermis, and subcutaneous tissues or hypodermis.
These all overlay soft tissue comprising of fascia, and muscle, which cover bone. There are a couple of important things to note. The major blood supply to the skin is located in an area called the hypodermis or subcutaneous tissue. Muscle and bone however, utilize a separate blood supply. Bone receives its blood supply from the bone marrow, whereas muscle receives its supply from blood vessels within each myofascial grouping. Remember that while some specialized inflammatory cells reside in tissue, blood supplies the catalyst for inflammation. The endothelium is a single layer of squamous epithelial cells that line the inner surface of blood and lymphatic vessels.
This plays a major part in the control of inflammation similar to turning the dimmer switch up or down. Cell adhesion molecules along the endothelium control whether white blood cells, fluid and inflammatory proteins enter and exit the surrounding tissue from the vascular system. Practical tip, because of the different blood supplies, the localized inflammatory response in bone and muscle may be responding to a different balance of pro or anti inflammatory cytokines than the superficial layers of skin and soft tissue. The skin will become inflamed and heal at different rates than soft tissue and bone. This separation into compartments is a useful scheme in medical decision making. But it does not follow the classification schemes for skin disorders, which you will find if you open up a textbook.
The most common classification scheme for skin disorders is purely based on morphologic descriptions of the rash, such as macular, papular, patch, and plaque, which are defined based on size greater or less than 10 millimeters, and whether it is flushed with the skin or raised above it. Another way is to organize the disorders based on classical categories of inflammation, such as disorders of the innate immunity, disorders of acquired immunity, and disorders of physical barriers to pathogens. Ideally, inflammatory markers would help us categorize the presenting illness of our patient into one of these organizational schemes. In other words, if you test positive for X inflammatory marker, you're in group one of the differential diagnosis. If you test negative, you're in group two.
Unfortunately, none of these textbook organizational systems were designed with the use of inflammatory markers as a distinguishing characteristic. From a practical standpoint, it is more useful to use inflammatory markers in the evaluation of skin and soft tissue disorders in two main modes, determine the extent of inflammation and determine the response to treatment. To know the extent of inflammation, you must figure out if it's localized to compartments or systemic.
This quickly categorizes several disorders, and helps focus our evaluation. Determining how localized inflammation is helps determine the severity of a skin or soft tissue disorder. For instance, is this localized psoriasis, or is there likely to be psoriatic arthritis or psoriatic associated inflammatory bowel disease? After the treatment is started, check the inflammatory markers to determine if there is appropriate response to therapy. If inflammatory markers don't change, we would presume that a response to therapy is not seen and you most likely have one of three scenarios, the wrong diagnosis or etiology, the correct diagnosis and etiology, but an inappropriate treatment and or treatment failure or non adherence to therapy.
This allows you to determine your next steps in management. Obtain a referral from a specialist, obtain further testing to confirm your diagnosis or obtain more information as to why your treatment is failing. For instance, is it antibiotic resistance or non adherence? The great news is there have been advances that use specialize inflammatory markers to determine the exact diagnosis. The development of these tests will likely lead to a reclassification of skin disorders based on study results, just as we are experiencing with rheumatologic disorders.