INTRODUCTORY CASE (BULLOUS PEMPHIGOID)
A 77-year-old woman presents to a local emergency room after developing numerous blisters over her trunk and extremities. She reports that she recently developed an intensely pruritic (itchy) red rash, and the next morning she was alarmed when she woke and noticed large, painful blisters erupting within the rash. Examination shows numerous tense bullae with erythematous, indurated borders over the trunk and extremities. A dermatologist is called for consultation and performs a punch biopsy from the edge of one of the large blisters. Clinical image and results of hematoxylin and eosin staining are shown in Figure 21-1.
Microscopic examination is most notable for a split at the dermoepidermal junction. While this finding can be seen in other blistering disorders, it is perhaps most characteristic of bullous pemphigoid. Bullous pemphigoid is an autoimmune blistering disorder caused by formation of pathogenic antibodies to a component of hemidesmosomes, most importantly bullous pemphigoid antigen 2, which is necessary for binding of the superficial component of the skin, the epidermis, to the deeper component, the dermis. An accompanying inflammatory infiltrate with prominent eosinophils is also highly indicative of bullous pemphigoid. As discussed in the cases later, further diagnostic studies using immunofluorescence can often help to confirm the diagnosis.
Bullous pemphigoid. (A) Tense bullae overlying an erythematous base in bullous pemphigoid. Source: Courtesy of Dr. Diaz L. UNC Dermatology. (B) Hematoxylin and eosin stained biopsy with split at dermal–epidermal junction (arrow). (C) Direct immunofluorescence demonstrating linear staining of IgG at the basement membrane zone. Source: Image used with permission from Dr. Diaz L and Dr. Culton D, UNC Dermatology.
The skin is the largest organ in the body and serves as its external covering, separating our sometimes fragile interior from the dangers of our environment. It provides a barrier that protects the body from both physical and environmental threats. It also acts as the primary defensive layer of the immune system by preventing infectious organisms from entering the body. Additionally, the skin plays a significant role in thermoregulation and is important in preventing overheating or overcooling of the body.
In medicine, the skin is involved in a vast number of pathological conditions. While there are a large number of conditions that primarily and exclusively manifest in the skin, our external surface can also give us diagnostic clues to pathology taking place elsewhere in the body. Because there are such a large number of conditions affecting the skin, it is sometimes useful to think of the conditions that affect the skin in groups. These may include inflammatory, immune-mediated, neoplastic, and infectious processes. Study of the skin is not the sole realm of the dermatologist as almost every field or subfield in medicine requires at least a basic understanding of dermatopathologic conditions, and ...