Harrison's Internal Medicine Chapter 52. Approach to the Patient with a Skin Disorder APPROACH TO THE PATIENT WITH A SKIN DISORDER: INTRODUCTION The challenge of examining the skin lies in distinguishing normal from abnormal, significant findings from trivial ones, and in integrating pertinent signs and symptoms into an appropriate differential diagnosis. The fact that the largest organ in the body is visible is both an advantage and a disadvantage to those who examine it. It is advantageous because no special instrumentation is necessary and because the skin can be biopsied with little morbidity. . | Chapter 052. Approach to the Patient with a Skin Disorder Part 1 Harrison s Internal Medicine Chapter 52. Approach to the Patient with a Skin Disorder APPROACH TO THE PATIENT WITH A SKIN DISORDER INTRODUCTION The challenge of examining the skin lies in distinguishing normal from abnormal significant findings from trivial ones and in integrating pertinent signs and symptoms into an appropriate differential diagnosis. The fact that the largest organ in the body is visible is both an advantage and a disadvantage to those who examine it. It is advantageous because no special instrumentation is necessary and because the skin can be biopsied with little morbidity. However the casual observer can be misled by a variety of stimuli and overlook important subtle signs of skin or systemic disease. For instance the sometimes minor differences in color and shape that distinguish a melanoma Fig. 52-1 from a benign nevomelanocytic nevus Fig. 52-2 can be difficult to recognize. To aid in the interpretation of skin lesions a variety of descriptive terms have been developed to characterize cutaneous lesions Tables 52-1 52-2 and 52-3 as well as Fig. 52-3 and to formulate a differential diagnosis Table 52-4 . For instance the finding of scaling papules present in patients with psoriasis or atopic dermatitis places the patient in a different diagnostic category than would hemorrhagic papules which may indicate vasculitis or sepsis Figs. 52-4 and 52-5 respectively . It is also important to differentiate primary from secondary skin lesions. If the examiner focuses on linear erosions overlying an area of erythema and scaling he or she may incorrectly assume that the erosion is the primary lesion and the redness and scale are secondary while the correct interpretation would be that the patient has a pruritic eczematous dermatitis with erosions caused by scratching. Figure 52-1 Soukoi FiutiSi. Mtpor t L. Bnunvotd H wt SL Longo Ou. n JL. Loji l o Ji Harrison s Pnnaplas ryf Wtomn .
