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6. Follicular plugging with cornified cells is often present, as are pustules within or adjacent to follicles. III. Infections A. Molluscum Contagiosum 1. Molluscum contagiosum is a very common self-limited viral infection (poxvirus) spread by direct contact. 2. It is clinically characterized by multiple 1–4 mm skin colored umbilicated papules on the arms, legs, face, and axilla of children (Figure 3–4). 3. It is more common and extensive in children with atopic dermatitis. 4. It is sometimes seen on the penis, vulva, inguinal areas and buttock in adults.

Chapter 3: Skin 37 Table 3–2. Dermatopathology terminology. Term Description Acantholysis Loss of keratinocyte cell-cell adhesion resulting in round rather than polygonal appearing cells Acanthosis Hyperplasia of the epidermis Atrophic Thinning; reduction in size or amount Dyskeratosis Abnormal cornification occurring (prematurely) in keratinocytes of the spinous layer Hypergranulosis Hyperplasia of the stratum granulosum Hyperkeratosis Increased thickness of stratum corneum Lichenification Hyperkeratosis, hypergranulosis, acanthosis and fibrosis of the papillary dermis corresponding to clinical skin thickening Lichenoid A band-like inflammatory infiltrate (usually lymphocytes) below the dermal-epidermal junction Orthokeratosis Stratum corneum without retention of nuclei Parakeratosis Retention of nuclei within the cornified cells of the stratum corneum Pedunculated A papule connected to the skin by a stalk thinner than the lesion itself Psoriasiform Inflammatory pattern: epidermis with thickening and elongation of rete ridges Spongiosis Intercellular edema between the keratinocytes of the spinous layer Vacuolar alteration Alteration including vacuole formation in cells of the basal layer 2.

It is also used to test for gene amplifications. IV. Common Inherited Diseases A. Trisomy (discussed in detail in Chapter 19). B. Monosomy (discussed in detail in Chapter 19). Chapter 2: Molecular Diagnostics 29 C. Huntington Disease 1. Huntington disease is a devastating adult-onset neurodegenerative disease that leads to progressive motor dysfunction, personality changes, and gradual cognitive loss. 2. It is caused by an autosomal dominant trinucleotide expansion (CAG repeats) within the Huntington gene.