There are many conditions that can have truncal involvement. This section focuses on some common eruptions that frequently affect the trunk: papulosquamous disorders; urticarial and morbilliform disorders; blistering disorders; and miscellaneous disorders. Urticaria and angioedema are discussed in chapter 14, "Anaphylaxis, Allergies, and Angioedema." Although the truncal location of an eruption can be a helpful clue for diagnosis, the clinical appearance of the lesions and overall assessment of the patient are needed to make the correct diagnosis.
Scaling conditions include psoriasis, seborrheic dermatitis, tinea corporis, pityriasis ("tinea") versicolor, eczema/atopic dermatitis, lichen planus, secondary syphilis, and scabies. Table 251-1 lists common features distinguishing these eruptions.
TABLE 251-1Comparison Features of Common Papulosquamous Eruptions |Favorite Table|Download (.pdf) TABLE 251-1 Comparison Features of Common Papulosquamous Eruptions
|Condition ||Distinguishing Clinical Features ||Location ||Special Signs ||Comments |
|Psoriasis ||Erythematous, well-marginated papules and plaques with silvery scale ||Trunk, extensor surfaces, scalp ||Auspitz sign; Koebner phenomenon, nail pitting ||Hereditary predilection; onset in early 20s |
|Seborrheic dermatitis ||Greasy, yellow scales ||Midchest, suprapubic, scalp, facial creases ||Can overlap with psoriasis, "sebopsoriasis" ||Debilitated, elderly, or infants (cradle cap) |
|Atopic dermatitis ||Ill-defined vesicles forming plaques with scale; chronic lesions lichenified ||Flexures > trunk ||Spares the nose ||Pruritus "itch that rashes"; atopic individuals |
|Lichen planus ||5 P's: purple, pruritic, polygonal, planar papules ||Any skin, mucous membranes, hair follicles ||Wickham striae; Koebner phenomenon ||Age 20–60 y old |
|Pityriasis rosea ||Lines of skin tension, collarette of scale ||Trunk, in Christmas tree pattern following skin lines ||Herald patch 1–2 wk before general eruption ||Spring and fall, age 15–40 y old; viral exanthem, herpes 6 and 7 |
|Tinea corporis ||Sharply demarcated, erythematous, scaly annular plaques; may coalesce into gyrate patterns ||Trunk, legs, arm, neck ||May need KOH/culture to diagnose; septate branching hyphae on KOH ||All ages; from pets, soil, or autoinoculation from hands/feet; incubation days or months |
|Pityriasis (tinea) versicolor ||Versicolored—red, salmon, light brown, dark brown, hypopigmented; well-demarcated scaly patches ||Central upper chest and back ||Spaghetti and meatballs on KOH; nonseptate pseudohyphae and budding yeast ||Young adults, summer, hot humid environments |
|Secondary syphilis ||At 2–10 wk, macular erythema on trunk, abdomen, inner extremities; followed by papular or papulosquamous lesions ||Palms, soles, trunk ||Serology ||Great masquerader—can take any form; can be confused with pityriasis rosea |
|Scabies ||Pruritic papules and burrows with crusting ||Finger webs, wrists, axillae, areolae, umbilicus, abdomen, waistband, genitals ||Scrapings show mites, feces, eggs ||Can be chronic "7-year itch"; intensely pruritic, especially at night |
Psoriasis is discussed in detail in chapter 253, "Skin Disorders: Extremities." Stress or alcohol ingestion can be associated with a flare of psoriasis. The following medications can also be related to an exacerbation: steroid withdrawal, lithium, β-blockers, interferon, and antimalarials.1 The differential diagnosis is listed in Table 251-1.
Diagnosis is clinical. The disorder is characterized ...