At the dermatology clinic, 58 year old Alan presents complaining of painful lesions on his skin and mouth for the past two months. On examination, there are flaccid bullae with erosions all over his trunk and extremities, as well as erosions on the oral and gingival mucosa. When lateral pressure is applied to a lesion, the outermost layer seems to slough off.
On the same day, 17 year old Gabriella comes in with an intensely itchy rash that appeared a couple of weeks ago. She has also experienced frequent nausea and diarrhea after meals. Physical examination shows multiple papules, vesicles, and bullae on both of her knees, forearms, and elbows, as well as her back and buttocks. Lab tests reveal elevated levels of anti-gliadin IgA and IgM. Based on the initial presentation, Alan and Gabriella seem to have some form of vesiculobullous or desquamating skin disorder.
Okay, first, let’s talk about physiology real quick. Normally, the skin is divided into three main layers, the epidermis, dermis, and hypodermis. The hypodermis is made of fat and connective tissue that anchors the skin to the underlying muscle. Above the hypodermis is the dermis, containing hair follicles, nerve endings, glands, blood and lymph vessels. And above the dermis is the epidermis, which contains 5 layers of developing keratinocytes.
Keratinocytes start their life at the lowest layer of the epidermis, so the stratum basale or basal layer. As keratinocytes in the stratum basale mature, they migrate into the next layers of the epidermis, called the stratum spinosum, stratum granulosum, stratum lucidum, and finally, the stratum corneum, which is the uppermost and thickest epidermal layer.
Before we dive into the various inflammatory skin disorders, there are several high yield terms to describe skin lesions. The most important here are the vesicles, which are up to 1 centimeter in diameter and look like clear blisters filled with fluid, and bullae, which are fluid-filled blisters larger than 1 centimeter.
All right then, onto vesiculobullous and desquamating skin disorders! Let’s start with autoimmune blistering diseases, which are a group of autoimmune disorders that affect the skin and mucous membrane like those found in the mouth. They are caused by a type II hypersensitivity reaction. That’s when the immune system B cells produce antibodies that bind to the body's own proteins. A disorder belonging to this group is pemphigus vulgaris, which is mainly seen in adults between the age of 40 and 60.