Folliculopapular eruptions | Acne | Presents in adolescence Waxing and waning lesions Inflammatory papules, pustules, comedones, and nodulocysts | Face, chest, and back | 29–2 |
| Rosacea | Presents in adults Telangiectasias and persistent centrofacial erythema, occasionally with inflammatory red papules and papulopustules | Face | 29–3 |
Blistering disorders | Herpes zoster | Closely grouped vesicles on an erythematous base Over 2–3 days, the lesions become pustular and then crust over after 7–10 days Pain and paresthesias over involved dermatome may precede the rash | Single, unilateral dermatome | 29–4 |
| Bullous impetigo | Presents as flaccid, transparent bullae that rupture easily and leave a rim of scale and shallow moist erosion Usually seen in children | Intertriginous areas | 29–5 |
| Bullous arthropod bites | A cluster of large, tense blisters on exposed skin | Most common on the extremities | 29–7 |
| Bullous pemphigoid | Seen in elderly patients Sudden onset of 1–2 cm tense blisters and bright, red, urticarial plaques | Begin on the lower extremities and progresses upward | 29–8 |
| Stevens-Johnson syndrome | Targetoid or macular patches with dusky centers that subsequently blister and then erode The skin is usually excruciatingly tender The lips are typically eroded and become covered with hemorrhagic crust) | Begins on chest and face and then spreads Palms and soles often involved Mucosal surfaces (lips, conjunctiva, genitals) may be involved | 29–9 |
Papulosquamous eruptions | Psoriasis | Well-demarcated erythematous plaques with silvery, adherent scales | Extensor surfaces, umbilicus, and scalp (Trunk and proximal extremities for guttate psoriasis) | 29–10 |
| Pityriasis rosea | “Herald patch” progressing to small, oval, scaly plaques in a “fir tree pattern” | Trunk | 29–11 |
| Tinea corporis | Round, pink plaques with small peripheral papules and an advancing scaling border | Anywhere | 29–12 |
| Nummular dermatitis | Extremely pruritic rash of numerous, round, crusted lesions | Legs | 29–13 |
| Secondary syphilis | Oval red/brown macules presenting diffusely, including palms and soles A history of a transient, painless, genital ulcer in the preceding weeks can often be obtained | Rash can be diffuse including palms and soles | |
Skin cancers | Basal cell carcinoma | Flesh-colored, translucent, or slightly red papule or nodule, classically displaying a rolled border | Head, neck, or other sun-exposed skin | 29–16 |
| Squamous cell carcinoma | Firm, but somewhat indistinct nodule or rough plaque | Sun-exposed skin | 29–17 |
| Melanoma | Dark brown to black macule with pigment variation and irregular borders | Anywhere | 29–18 |
Purpura and petechiae | Petechiae | Nonblanching, pinpoint, red spots | Dependent body parts, most commonly the lower extremities | 29–15 |
| Purpura | Red, blue or purple nonblanching macules, papules or plaques, may or may not be palpable, up to several centimeters in diameter | Anywhere | |