Rash
Rash: Excerpt from Pediatric Complaints and Diagnostic Dilemmas
Heather C. Forkey
Approach to the Patient with Rash
I. Definition of the Complaint
Rash, a general term applied to any skin eruption, is the presenting problem or
secondary complaint for 20% to 30% of visits to pediatricians, emergency
departments, and primary care practitioners. Perhaps because rashes are so
common and because the skin is the easiest organ of the body to access,
patients with skin complaints may receive only cursory examinations and overly
hasty diagnoses.
Rashes may be divided into primary and secondary lesions. The primary lesion is
the most representative lesion and arises from the disease process itself
without alteration by the patient or therapies. Examination of the primary
lesion is most helpful in making a specific diagnosis. Secondary lesions result
from changes caused by the patient or environment, usually from scratching,
medication use, or infection. These change over time. Although they do not
usually identify the primary cause, they do give historical clues to the
primary lesions.
There are a variety of primary lesions. A macule is a flat, nonpalpable area of color change to the skin in any shape. Papules are raised lesions less than 0.5 cm in diameter. Nodules are raised lesions larger than 0.5 cm in diameter, and tumors are larger nodules, usually greater than 2 cm in diameter. Plaques are well-circumscribed, wide-based lesions usually created by the convergence
of a number of papules. The diameter of a plaque is usually greater than its
height.
Wheals are raised edematous lesions of various sizes that are transient in nature and
white, pink, or red in color.
Vesicles are raised, fluid-filled lesions smaller than 1 cm in diameter, and bullae are similar but greater than 1 cm in diameter. Cysts are circumscribed tumors that contain fluid or soft contents. Pustules are raised, well-demarcated lesions with purulent material inside, and they are
usually white or yellow in appearance.
Petechiae are pinpoint areas of hemorrhage that are caused by leakage of blood into the
skin.
Purpura is the leakage of blood into the skin that results in a flat or elevated
lesion. Neither purpura nor petechiae blanch when pressure is applied.
Burrows are linear lesions caused by the movement of parasites in the skin.
Secondary lesions include scales, which are accumulations of dried layers of squamous cells. Scales can appear
greasy, yellowish, or silvery.
Crusts are made by dried exudate overlying damaged skin. Excoriations are usually caused by scratching; they are linear lesions of skin that usually
indicate pruritus.
Erosions are lesions of denuded epidermis, and ulcers signify a deeper loss of skin into the dermis or subcutaneous tissue. Fissures are linear clefts of the epidermis to the dermis. Lichenification is an exaggeration of skin markings caused by chronic rubbing or scratching. A scar is permanent fibrotic tissue that is found when there has been deep injury to
the skin.
Atrophy is the loss or thinning of the epidermis or dermis.
One of the values of identifying primary lesions and differentiating them from
secondary lesions is that doing so allows classification into broad groups of
skin disorders that can narrow the differential. These categories are
papulosquamous, vesicobullous, tumor-nodule, vascular reaction, eczematous, and
pigmentary changes.
Two additional terms define a constellation of findings rather than primary or
secondary lesions.
Eczematous lesions are erythematous inflammatory skin lesions that have poorly defined
borders and can acutely become vesiculated. Scale, crust, and lichenification
may be seen over time.
Hyperkeratosis describes lesions with thick and adherent scale.
II. Complaint by Cause and Frequency
Causes of rashes may be grouped by age and frequency (Table 9-1).
III. Clarifying Questions
The history is vitally important in narrowing the differential diagnosis of skin
lesions. Because rash can be the primary manifestation of systemic disease,
general questions relating to the child
's overall health are important. Determination of age, gender, and racial or
ethnic background may be useful, because some skin disorders are found only in
particular age groups or are seen more commonly in specific subsets of the
population. Specific questions that help narrow the diagnosis include the
following.
• What was the progression of the rash over time and the duration of the rash?
— Viral exanthems can be defined by where they start and where they spread. For
example, measles begins at the scalp and hairline and progresses downward,
whereas scarlet fever begins on the upper trunk. Duration varies with different
types of rashes. Pityriasis rosea may last for weeks, whereas viral exanthems
are more limited.
• What is the configuration of the lesion?
— The shape of the lesion can often be characteristic or provide clues to the
etiology. Linear lesions include contact dermatitis and lichen striatus, a
self-limited papular dermatitis. Annular lesions, which are ring shaped with
central clearing, include tinea corporis, pityriasis rosea, and nummular
eczema. Arciform lesions are arc-like or semicircular and are found in erythema
multiforme and erythema marginatum.
• Where is the rash distributed on the body?
— Lesions limited to a particular dermatome may be characteristic of herpes
zoster. If contact dermatitis is being considered, the distribution of the rash
must be consistent with the area in contact with the suspected irritant.
Knowing the typical patterns of disorders in particular types of patients may
guide diagnosis. Scabies rarely involves the face, except in infants. Atopic
dermatitis is found in the flexural areas of the older child, whereas psoriasis
involves extensor surfaces.
• What is the color of the rash?
— Pigmentation and erythema are clues to the disease process. Pigment changes can
include hyperpigmentation and hypopigmentation and usually indicate
postinflammatory changes due to increases or decreases in melanin production.
Depigmentation is the loss of pigment resulting from an autoimmune effect or
congenital disorder.
IV. References
1. Hurwitz S. Clinical pediatric dermatology: a textbook of skin disorders of childhood and
adolescence,
2nd ed. Philadelphia: WB Saunders, 1993:1–6.
2. Pomeranz AJ, Fairley JA. The systematic evaluation of the skin in children. Pediatr Clin North Am 1998;45:49–63.
3. Shivaram V, Christoph RA, Hayden G. Skin disorders encountered in a
pediatric emergency department.
Pediatr Emerg Care 1994;9:202.
4. Tunnessen WW Jr. A survey of skin disorders seen in pediatric general and
dermatology clinics.
Pediatr Dermatol 1982;1:219.
5. Weston W, Lane AT, Morelli JG. Color textbook of pediatric dermatology, 2nd ed. St. Louis: Mosby, 1996:1–16.
Pictures
Book Source Details
- Book Title: Pediatric Complaints and Diagnostic Dilemmas
- Author(s): Samir S Shah MD; Stephen Ludwig MD
- Year of Publication: 2003
- Copyright Details: Pediatric Complaints and Diagnostic Dilemmas, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
» Next page: Rash - Case 9-2: 7-Week-Old Girl (Pediatric Complaints and Diagnostic Dilemmas)
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