The trunk is a general term for the core body region including the chest, abdomen, flanks, and back. The trunk has many unique characteristics. In many people it is a site of minimal sunlight exposure as it is usually covered by clothing. Dermatoses within this distribution may be caused by an allergic contact dermatitis due to chemicals in clothing, soaps, dryer sheets, and other allergens. Since the trunk is generally covered by clothing, this occlusion often creates a warm, humid environment ideal for the development of diseases such as folliculitis, acne, and tinea versicolor. A high density of sebaceous glands in the presternal area may provide an ideal location for pityrosporum ovale yeast proliferation, making this a common location for seborrheic dermatitis. Skin folds, such as the abdominal skin folds and inframammary creases are prone to intertrigo and/or maceration, increasing the risk of developing cutaneous candida infections among other dermatoses. The trunk is the most common location for herpes zoster. The umbilicus is unique in that it has a high density of apocrine glands. Interestingly some conditions including psoriasis and scabies often favor this site.
Skin diseases primarily involving the trunk can be broadly categorized into inflammatory dermatoses, infections, and pilosebaceous diseases (see Table 34-1). The inflammatory diseases are the most common cause of skin disease on the trunk, however infectious skin diseases are more common in hot humid climates, in obese or immunocompromised patients. The trunk is the area of the body that is most involved in diseases such as morbilliform drug rashes, guttate psoriasis, tinea versicolor, and pityriasis rosea.
| Disease | Epidemiology | History | Physical Examination |
|---|---|---|---|
| Inflammatory | |||
| Allergic contact dermatitis | Common F > M Age: any age | Pruritus Onset: hours to days after contact with allergen | Acute: papules and/or vesicles on an erythematous base (Figures 8-4 and 8-5) Chronic: xerosis, fissuring, hyperpigmentation, and lichenification (Figures 8-1, 8-2, 8-3). Typical locations: axillae, waistline, and umbilicus |
| Psoriasis | Common M = F Age of onset: any age but peaks in 20s and 50s | Asymptomatic or mildly pruritic. Chronic May have history of arthritis and family history of psoriasis | Red papules and plaques with silvery, thick, adherent scale typically on lower back, umbilicus, buttocks, and gluteal cleft. Guttate psoriasis presents with multiple small scaly papules (Figure 9-5) |
| Seborrheic dermatitis | Common M > F Age: bimodal; peaks in infancy and adulthood | Asymptomatic or mildly pruritic. Intermittent with seasonal variation | Symmetric pink plaques with greasy scale on central chest |
| Pityriasis rosea | Common F > M Age: any, most common in children and young adults Seen in fall or spring | Variable pruritus, sometimes preceding nonspecific “flu-like” symptoms Spontaneous remission in 6-12 weeks | Begins with a herald patch, an oval, slightly elevated, salmon pink 2-5 cm plaque with trailing collarette scale. Later dull pink oval papules or plaques with fine scale develop symmetrically on trunk in “Christmas tree” distribution (Figure 9-9) |
| Infectious | |||
| Candidiasis | Common M = F Age: infants and adults, other ages when risk factors present | Pruritus, soreness Risk factors: pregnancy, immunodeficiency, obesity, diabetes, antibiotic and glucocorticoid use | Initially vesicopustules that rupture and coalesce leading to moist, macerated, red plaque with fissures with satellite pustules at periphery on inframammary, axillae, and abdominal skin folds (Figure 10-17) |
| Tinea versicolor | Common M = F Age: postpubertal | Asymptomatic rarely mild pruritus Duration: months to years. More common in summer and warm moist environments | 3-5 mm round to oval macules with fine scale, may coalesce and develop hypo- or hyperpigmentation or variable coloration on central back and chest and neck (Figure 10-14) |
| Tinea corporis | Common M = F Age: any, most common in preadolescents | Asymptomatic or mild pruritus. Spread by direct contact with infected humans, animals, soil, or autoinoculation from a dermatophyte infection present on other locations | Red, scaly papule that expands outward and develops into annular plaque with slightly raised well-demarcated border with peripheral scale (Figure 10-4) Central clearing may result in a “target-like” appearance |
| Folliculitis | Common M:F dependent upon etiology which may include non-infectious causes Age: any | Variable pruritus. Risk factors: occlusion, heat, humidity, diabetes, immunosuppression, trauma, and medications | Follicular-based papules or pustules May have surrounding red zone May have erosions or crust from secondary changes (Figures 15-8 & 15-9) |
| Infectious exanthems | Common Age: <20 years Viral pathogen most common, can be bacterial, mycoplasmal, rickettsial, or other | Prodromal symptoms including fever, malaise, coryza, sore throat, nausea, vomiting, diarrhea, abdominal pain, and headache Usually precedes cutaneous eruption by up to 3 weeks | Multiple presentations: scarlatiniform, morbilliform (Figures 27-1, 27-2, 27-3, 27-4, 27-5, 27-6), vesicular, and pustular Often accompanied by oral mucous membrane involvement, lymphadenopathy, hepatomegaly, and splenomegaly |
| Syphilis (secondary) | Uncommon M > F Age: 15-40 Risk factors: men who have sex with men | History of asymptomatic, genital ulcer several weeks to months prior to onset of rash. Systemic symptoms (fever, malaise, myalgia, and headache). May be present or shortly precede onset of eruption | Scattered ill-defined pink macules or red, scaly, well-defined papules symmetrically distributed on trunk (Figure 12-6) |
| Herpes zoster | Common M:F unknown Age: any age, but usually >50 years | Severe pain, paresthesias, or pruritus precedes eruption. Resolves over 2-3 weeks | Grouped vesicles on an erythematous base (Figure 11-4) that later crusts over a unilateral dermatome (usually thoracic) |
| Pilosebaceous | |||
| Acne | Common Teens: M > F Adults: F > M Age: adolescents and young adults | Asymptomatic, pruritic, or tender. Individual lesions may last weeks to months. Variable course Menstrual exacerbations | Open (black heads) and closed (white heads) comedones, erythematous papules, pustules, and nodules on upper chest and back (Figure 15-1) |
| Other | |||
| Drug eruption | Common F > M Age: any, most common in hospitalized patients | Symptoms, onset, and duration variable and depend on offending agent. History of recent changes or adjustments to medications Risk factors: elderly, concomitant viral infection | Morphology and distribution extremely variable, virtually every cutaneous reaction may be seen. Morbilliform most common, presents with small pink macules and papules, often starts on trunk and pressure-bearing areas, may generalize and become confluent (Figure 10-6) |
| Grover’s disease (transient acantholytic dermatosis) | Uncommon M > F Age: ≥50 | Variable pruritus Abrupt onset with chronic course. Exacerbated by heat, sweat, sunlight, fever, and bedridden status | Discrete, scattered, and/or confluent red hyperkeratotic scaly papules sometimes with crust, erosion on central trunk, and proximal extremities |
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