Evaluation of rash in children

Rash in children is common. The differential diagnoses are extensive, ranging from self-limiting conditions (e.g., roseola) to life-threatening illnesses such as meningococcal disease.

Rash may be the first indication of a potentially serious multiorgan disease or sepsis and should be carefully evaluated (see Urgent considerations).

Rash may be categorized as maculopapular, pustular, vesiculobullous, diffuse/erythematous, or petechial/purpuric in nature. In many etiologies these forms may coexist or evolve from one form to another.

Initial considerations in evaluating a rash in children include the morphology, duration, and distribution. Age, sex, family history, medications, known allergies, and exposures are also of primary importance.

Generally, rash in the absence of fever or systemic symptoms is not urgent.

Definitions

• Macule: a flat area of color change <1 cm in size (e.g., viral exanthem [such as measles and rubella], morbilliform drug eruption).

• Patch: a large macule >1 cm in size (e.g., viral exanthem [such as measles and rubella], morbilliform drug eruption).

• Papule: a raised area <1 cm in size (e.g., wart).

• Nodule: a larger papule, >1 cm in size (e.g., nodular prurigo).

• Plaque: a flat-topped raised area (a cross between a nodule and a patch; e.g., psoriasis).

• Vesicle: a small fluid-filled lesion (blister) <0.5 cm in size (e.g., varicella, eczema herpeticum).

• Bulla: a larger vesicle >0.5 cm (e.g., bullous impetigo).

• Pustule: a pus-filled lesion (e.g., folliculitis).

• Wheal: a transient raised papule or plaque caused by dermal edema (e.g., urticaria).

• Scale: flakes of stratum corneum (e.g., eczema, psoriasis).

• Crust: dried serum, blood, or purulent exudate on the skin surface (e.g., impetigo).

• Erosion: loss of epidermis, heals without scarring (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis).

• Ulcer: loss of epidermis and dermis, heals with scarring (e.g., venous ulcer, pyoderma gangrenosum).

• Excoriation: loss of epidermis following trauma such as scratching (e.g., as can be seen in eczema).

• Fissure: a split in the skin (e.g., angular cheilitis, palmoplantar keratoderma).

• Lichenification: thickening of the skin with accentuation of skin markings (e.g., chronic eczema, lichen simplex chronicus).

• Purpura: an area of color change (red or purple) due to bleeding into the skin; does not blanch on pressure (e.g., vasculitis, disseminated intravascular coagulation).

• Petechia: a pin-point purpuric lesion (e.g., vasculitis, disseminated intravascular coagulation).

• Ecchymosis: a larger area of purpura (e.g., vasculitis, disseminated intravascular coagulation).

• Annular: ringed lesions.

• Malar: also known as "butterfly rash"; a symmetrical fixed erythematous maculopapular lesion with slight scale occurring over both cheeks and nose, sparing the nasolabial folds.

This topic covers the evaluation of rash in children.

For evaluation of rash by lesion type and including adult populations, see Evaluation of maculopapular rash; Evaluation of pustular rash; Evaluation of vesicular-bullous rash.​