Introduction A drug reaction can be defined as an undesirable response evoked by a medicinal substance. Any drug is a potential cause of an adverse reaction, although certain classes of drugs can be incriminated more often than others. Major offenders include antibiotics (particularly the newer ones and oral antifungal agents), nonsteroidal antiinflammatory drugs (NSAIDs), psychotropic agents, β-blockers, calcium channel blockers, thiazides, angiotensin-converting enzyme (ACE) inhibitors, and…

Not unexpectedly, there are conditions encountered in dermatopathology that defy orderly classification, having neither a consistent tissue reaction pattern nor a recognized infectious cause. However, in the case of confluent and reticulated papillomatosis, current evidence does point to an infectious etiology. Papuloerythroderma has many features suggesting a relationship to mycosis fungoides. Reclassification of these two entities is likely in the near future. Accessory Tragus Accessory tragi…

Introduction This chapter covers a diverse group of diseases that have in common a disturbance in metabolism or body function. Many of these conditions have a genetic basis, most of which have been elucidated in the past three decades. Three major disease categories are considered in this chapter: Vitamin and dietary disturbances Lysosomal storage diseases Miscellaneous metabolic and systemic diseases. The various diseases included in these…

Introduction The panniculus adiposus (subcutaneous fat) is a metabolic depot that also functions as a layer of insulation and as a buffer to trauma. It is composed of mature lipocytes, which are round to polygonal cells with an eccentric nucleus and a large cytoplasmic lipid vacuole. In contrast, fetal fat cells contain multiple small lipid vacuoles. The lipocytes are separated from their neighbors by an inconspicuous…

Introduction A cyst is an enclosed space or abnormal sac within a tissue, usually containing fluid or semisolid matter and lined by epithelium. Cysts are usually classified on the basis of their pathogenesis. In the skin, the most important cysts are derived from the dermal appendages as retention cysts. The developmental cysts, which result from the persistence of vestigial remnants, are much less common. The term…

Introduction This chapter covers the nontumorous disorders of the cutaneous appendages, the great majority of which are inflammatory diseases of the pilosebaceous apparatus. Inflammation of the apocrine and eccrine glands is quite uncommon by comparison. Hamartomas and some related congenital malformations are included with the appendageal tumors in Chapter 34 ( pp. 952, 972, 982 ). The following categories of appendageal diseases are considered in this…

Introduction Cutaneous deposits are a heterogeneous group of substances that are not normal constituents of the skin. They are laid down, usually in the dermis, in a variety of different circumstances. There are five broad categories of deposits ( Table 15.1 ). The first group includes calcium salts, bone, and cartilage. The second category includes the hyaline deposits. These have an eosinophilic, somewhat glassy appearance in…

Introduction The mucinoses are a diverse group of disorders that have in common the deposition of basophilic, finely granular, and stringy material (mucin) in the connective tissues of the dermis (dermal mucinoses), in the pilosebaceous follicles (follicular mucinoses), or in the epidermis and tumors derived therefrom (epithelial mucinoses). The most important mucinoses are the dermal ones where glycosaminoglycans (GAGs), also known as acid mucopolysaccharides, accumulate in…

Introduction Normal elastic tissue Elastic fibers are the important resilient component of mammalian connective tissue, and their presence is necessary for the proper structure and function of the cardiovascular, pulmonary, and intestinal systems. Their structural role is to endow tissues with elastic recoil and resilience. They constitute less than 4% of the dry weight of the skin, forming a complex and extensive network in the dermis…

Introduction Collagen is the major structural constituent of mammalian connective tissues. It accounts for well over 70% of the dry weight of the skin. There are at least 10 genetically distinct types of collagen, and it is the relative content of these different collagen types, as well as the amount of elastic tissue and nonstructural constituents such as the proteoglycans, that determines the specific biomechanical properties…

Introduction This chapter deals with the various disorders of cutaneous pigmentation, excluding those entities in which there is an obvious lentiginous proliferation of melanocytes in sections stained with hematoxylin and eosin (H&E); it also excludes tumors of the nevus cell–melanocyte system. Both of the excluded categories are discussed in Chapter 33 . Cutaneous pigmentation may also result from the deposition of drug complexes in the dermis.…

Introduction This chapter deals with a heterogeneous group of diseases in which an abnormality of maturation, of keratinization, or of structural integrity of the epidermis is present. Many advances have been made in the past decade in our understanding of the molecular basis of these disorders. Most of these conditions are genetically determined, although a few are acquired diseases of adult life. An understanding of these…

Introduction Cutaneous blood supply The skin is supplied by small segmental arteries that may reach the skin directly or after supplying the underlying muscle and soft tissues en route. These vessels branch to supply the subcutis with a meshwork of arteries and arterioles. In the dermis, there is a deep (lower) horizontal plexus , situated near the interface with the subcutis, and a superficial (upper) horizontal…

Introduction The granulomatous reaction pattern is defined as a distinctive inflammatory pattern characterized by the presence of granulomas. Granulomas are relatively discrete collections of histiocytes or epithelioid histiocytes with variable numbers of admixed multinucleate giant cells of varying types and other inflammatory cells. Conditions in which there is a diffuse infiltrate of histiocytes within the dermis, such as lepromatous leprosy, are not included in this reaction…

Introduction The vesiculobullous reaction pattern is characterized by the presence of vesicles or bullae at any level within the epidermis or at the dermoepidermal junction. Pustules, which are vesicles or bullae containing numerous neutrophils or eosinophils, are included in this reaction pattern. Vesiculobullous lesions result from a defect, congenital or acquired, in the adhesion of keratinocytes. Accordingly, it is important to understand the mechanisms involved in…

Introduction The spongiotic tissue reaction is characterized by the presence of intraepidermal and intercellular edema (spongiosis) ( Fig. 6.1 ). It is recognized by the widened intercellular spaces between keratinocytes, with elongation of the intercellular bridges ( Fig. 6.2 ). The foci of spongiosis may vary from microscopic in size to grossly identifiable vesicles and even bullae. Mild spongiosis is well seen in semi-thin sections. Inflammatory…

Introduction The psoriasiform reaction pattern is defined morphologically as the presence of epidermal hyperplasia with elongation of the rete ridges in a regular manner. This definition encompasses a heterogeneous group of dermatological conditions. This morphological concept is much broader than the pathogenetic one, outlined by Pinkus and Mehregan. They considered the principal features of the psoriasiform tissue reaction to be the formation of a suprapapillary exudate…

Introduction The lichenoid reaction pattern (lichenoid tissue reaction, interface dermatitis) is characterized histologically by epidermal basal cell damage. This takes the form of cell death and/or vacuolar change (liquefaction degeneration). The cell death usually involves only scattered cells in the basal layer that become shrunken with eosinophilic cytoplasm. These cells, which have been called Civatte bodies, often contain pyknotic nuclear remnants. Sometimes, fine focusing up and…

In the previous chapter, an orderly approach to the diagnosis of inflammatory skin lesions was discussed. This chapter records in list form some useful points that may assist in reaching a correct diagnosis. Many of the clues that follow produce diagnostic lists that are not necessarily related to tissue reaction, etiology, or pathogenesis. Some of the clues that follow are original observations; many have been around…

Introduction Dermatopathology requires years of training and practice to attain an acceptable level of diagnostic skill. Many have found this process an exciting and challenging one, well worth the expenditure of time and intellectual effort. To the trainee, there seems to be an endless number of potential diagnoses in dermatopathology, with many bewildering names. However, if a logical approach is adopted, the great majority of skin…