Page 865 - Robbins Basic Pathology by Vinay Kumar, Abul K. Abbas, Jon C. Aster
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Skin
CHAPTER CONTENTS
Acute Inflammatory Dermatoses 852 Lichen Simplex Chronicus 856 Bullous Pemphigoid 859
Urticaria 852 Infectious Dermatoses 856
Bacterial Infections 856 Dermatitis Herpetiformis 861
Acute Eczematous Dermatitis 852 Benign and Premalignant Tumors 862
Fungal Infections 857 Benign and Premalignant Epithelial
Erythema Multiforme 853 Lesions 862
Chronic Inflammatory Dermatoses 854 Verrucae (Warts) 857
Psoriasis 854 Blistering (Bullous) Disorders 857 Malignant Epidermal Tumors 863
Pemphigus (Vulgaris and Foliaceus) 858
Lichen Planus 855 Melanocytic Proliferations 865
Skin diseases are common and diverse, ranging from irri- these diseases, it is important to appreciate that the practice
tating acne to life-threatening melanoma. Many are intrin- of dermatopathology relies on close interactions with clini-
sic to the skin, but some are manifestations of diseases cians, particularly dermatologists. The clinical history and
involving many tissues, such as systemic lupus erythema- the gross appearance and distribution of lesions reported
tosus or genetic syndromes such as neurofibromatosis. In by clinicians are often as important as the microscopic find-
this sense, the skin is a uniquely accessible “window” ings in arriving at a diagnosis.
through which numerous disorders can be viewed and
recognized. Diseases of the skin can be confusing for the student,
in part because dermatologists and dermatopathologists
Skin is not a mere protective mantle but rather a complex use a large and unique lexicon to describe skin lesions.
organ that actively participates in regulated cellular and Because knowledge of this vocabulary forms the basis of
molecular events that govern the body’s interactions with clear understanding and communication, some of the
the external environment. It is constantly bathed with terms and descriptors that are most commonly used are
microbial and nonmicrobial antigens. These are processed defined below.
by intraepithelial Langerhans cells, which bear their anti-
genic cargo to regional lymph nodes and initiate immune Terms for Macroscopic Lesions
responses. Squamous cells (keratinocytes) help maintain Excoriation: Traumatic lesion breaking the epidermis
skin homeostasis by providing a physical barrier to envi- and causing a red linear mark (i.e., a deep scratch); often
ronmental insults and by secreting a plethora of cytokines self-inflicted.
that influence both the squamous and dermal microenvi- Lichenification: Thickened and rough skin character-
ronments. The dermis contains both CD4+ helper and ized by prominent skin markings; usually the result
CD8+ cytotoxic T lymphocytes, some of which home to the of repeated rubbing (see under “Lichen Simplex
skin by virtue of specialized receptors such as cutaneous Chronicus”).
lymphocyte antigen. The epidermis contains intraepithelial Macule: Flat, circumscribed area, 5 mm or less in diam-
lymphocytes, including γ/δ T cells, which constitute a com- eter, distinguished from surrounding skin by coloration.
ponent of the innate immune system. Local immune If greater than 5 mm, referred to as a patch.
responses involving these immune cells and cytokines Papule: Elevated dome- or flat-topped lesion 5 mm or
account for the microscopic patterns and clinical expres- less in diameter. If greater than 5 mm in diameter,
sions of cutaneous inflammatory and infectious diseases. referred to as a nodule.
Plaque: Elevated flat-topped lesion, usually greater than
This chapter focuses on a small subset of common and 5 mm in diameter.
pathogenically illustrative skin diseases. In considering Pustule: Discrete, pus-filled raised lesion.
The authors thank Drs. Ronald Rapini and Robert Jordan and the Scale: Dry, horny, platelike excrescence; usually the
Department of Dermatology at the University of Texas Medical School result of imperfect cornification.
at Houston for many of the clinical photographs in this chapter. The Vesicle: Fluid-filled raised area 5 mm or less in diame-
contributions of Dr. George Murphy to this chapter in previous ter. If greater than 5 mm in diameter, referred to as a
editions are gratefully acknowledged.
