Kara Trapp

Acute Generalized Exanthematous Pustulosis: AGEP

Acute generalized exanthematous pustulosis (AGEP) is a rare clinical entity characterized by an acute onset of numerous sterile, nonfollicular, pinhead-sized pustules arising on an erythematous, edematous base accompanied by fever (>38 C), neutrophilia, and occasionally eosinophilia. In 1968, Baker and Ryan reported 104 cases of pustular psoriasis and specifically detailed five patients whom they diagnosed as having “exanthematic pustular psoriasis” most likely due to a drug or infectious etiology. These five patients did not have a history of psoriasis and were characterized as having pustular skin reactions of acute onset that quickly resolved and did not recur. Subsequently, in 1980, Beylot et al. reviewed the existing literature regarding pustuloses and reported four additional cases; they are responsible for coining the name of this distinct entity as “acute generalized exanthematic pustulosis.” Additional literature reports by Macmillan in 1973 and Staughton and Harper in 1984 denote pustular skin eruptions most likely representing AGEP which they termed as “generalized pustular drug rash” and “toxic pustuloderma,” respectively.

Muir-Torre Syndrome

Sebaceous adenomas are benign adnexal tumors that have no malignant potential. They are of no clinical significance in isolation but may be indicators of internal malignancy when occurring as part of the Muir-Torre syndrome. Sebaceous adenomas grow as exophytic, yellowish papules and nodules. In most cases, these lesions are less than 1 cm in diameter (Rulon and Helwig. Cancer. 1974;33:82–102). While they may occur at any body site, they are most common on the face. They usually appear in middle age. Ulceration is not a common feature.

Mast Cell Disease: Urticaria Pigmentosa

Nettleship and Tay first described urticaria pigmentosa in 1869. It was not until 1949 that Ellis described increased numbers of mast cells in several organs, demonstrating the systemic involvement of mastocytosis. Most cases of urticaria pigmentosa are caused by a point mutation of the proto-oncogene c-kit at codon 816. C-kit functions as a transmembrane protein and is involved in signaling cell division when bound to mast cell growth factor. Mutations in the 816 position result in abnormal proliferation of mast cells.

Paget’s Disease

Mammary Paget’s disease was first described by Sir James Paget in 1874. Mammary Paget’s disease is an uncommon condition, representing about 1–4.3 % of all breast cancers. Extramammary Paget’s disease was first described by Radcliffe Crocker in 1889. There are currently two theories that postulate the development of Paget’s disease. The epidermotropic (ductal) theory holds that the Paget cells are duct cancer cells that have migrated along the basement membrane of the underlying ducts to the epidermis of the nipple. The second theory, in situ malignant transformation or degeneration from existing cells, postulates that the Paget cell is a malignant keratinocyte in situ; thus, this theory defines Paget’s disease as an in situ carcinoma without underlying cancer of the breast.

Graft-Versus-Host Disease

Graft-versus-host disease (GVHD) is arbitrarily divided into acute and chronic forms. The acute form of the disease ordinarily occurs between 21 and 60 days following bone marrow transplantation. Patients develop maculopapular or scarlatiniform eruptions. In the more severe forms of the disease, bullae may develop and progress to widespread desquamation in a toxic epidermal necrolysis-like pattern. The palms and soles are often involved early in the disease, while the trunk, neck, cheeks, and ears are commonly affected as the disease progresses.

Drug Reaction with Eosinophilia and Systemic Symptoms

Drug reaction (or rash) with eosinophilia and systemic symptoms (DRESS) was originally described in 1996 by Bocquet et al. in their description of patients who developed fever, a severe cutaneous reaction with infiltrated papules, facial edema, or an exfoliative dermatitis, lymphadenopathy, hematologic abnormalities (eosinophilia or atypical lymphocytes), and internal organ involvement within 2 months after initiation of the offending drug. The current literature defines DRESS as a syndrome with varying combination of the following factors: drug-induced immunological background, late onset drug reaction, longer duration than other drug rashes, multi-organ involvement, lymphocyte activation, eosinophilia, and frequent virus reactivation.

Blistering Disorders (Porphyria Cutanea Tarda and Pseudoporphyria)

Porphyria cutanea tarda (PCT) and pseudoporphyria represent the most common subtypes of porphyria presenting in patients with end-stage renal disease (ESRD). In these patients, there is a disorder of heme synthesis that produces a pathogenic accumulation of photosensitizing intermediary metabolites. The result of this disorder is a photodistributed pruritic blistering eruption as well as other characteristic clinical and laboratory findings. The distinction between PCT, pseudoporphyria, and other vesiculobullous disorders may be challenging. Thus, the aim of this chapter is to provide a comprehensive overview of the features, diagnostic markers, and treatment regimens for these common cutaneous entities observed in individuals with concurrent renal dysfunction.

T-Cell Pseudolymphoma Presenting in a Lichenoid and Nodular Pattern

The T-cell pseudolymphomas represent a heterogeneous group of skin disorders both clinically and histologically that have been subdivided into distinct clinicopathological entities. We describe a group of T-cell pseudolymphomas presenting in a lichenoid and/or nodular pattern. The disorders described in this chapter include lichenoid keratosis, lichen aureus, actinic reticuloid, lymphomatoid contact dermatitis, lymphomatoid drug reactions, and solitary T-cell pseudolymphomas. For each disorder, the definition, epidemiology, pattern of infiltration, cytomorphology, immunophenotype, cytogenetics, molecular findings, clinical behavior, and differential diagnosis are included, as well as associated histopathological images. The distinction between benign pseudolymphomas and malignant lymphomas is challenging and requires complete integration of clinical, histopathological, immunophenotypic, and molecular features. This chapter aims to describe a set of lichenoid and nodular reactive T-cell pseudolymphomas to better differentiate these benign atypical lymphoid infiltrates from the malignant cutaneous lymphomas they simulate clinically and histologically.