Rash, Pediatric

Basics

Description

Lesion morphology:
- Macule:
  - Localized nonpalpable changes in skin color
  - Purpura or petechiae (nonblanching with pressure)
- Maculopapule:
  - Slightly elevated lesions with localized changes in skin
- Papule:
  - Solid, elevated lesions <5 mm in diameter
  - Keratotic (rough-surfaced lesion)
  - Nonkeratotic (smooth lesion)
  - Palpable purpura (nonblanching with pressure)
- Plaque:
  - Solid, elevated lesions >5 mm in diameter
  - Often results from a confluence of papules
- Nodule:
  - Solid, elevated lesions extending deep into the dermis or SC tissue >5 mm in diameter
- Wheal:
  - Circular, irregular lesions varying from red to pale
- Vesicle:
  - Clear, fluid-filled lesions <5 mm in diameter
- Bullae:
  - Clear, fluid-filled lesions >5 mm in diameter
- Pustules:
  - Pus-filled lesions
Secondary lesions:
- Scales:
  - Thin plates of dried cornified epithelium partially separated from the epidermis
- Lichenification:
  - Dried plaques resulting in skin furrowing
- Erosion:
  - Moist surface uncovered by rupture of vesicles or bullae
- Excoriation:
  - Linear loss of the skin due to trauma
- Ulcer:
  - Deep loss of the skin involving the epidermis and a variable amount of the dermis and SC tissue
Configuration:
- Circles or arcs
- Serpiginous (creeping or worm like)
- Iris grouping (bull's eye appearance)
- Irregular grouping
- Zosteriform grouping
- Linear grouping
- Retiform grouping
Color of a lesion or the entire skin may be due to a number of substances:
- Red or red-brown lesions result from oxyhemoglobin found in RBCs
- The macular erythematous lesions seen in viral exanthema usually represent dilated superficial cutaneous vessels
- Purpura and petechiae result from leakage of RBCs out of the vascular space
- Hypopigmentation or hyperpigmentation represent postinflammatory change from either increases or decreases in melanin production
- Depigmentation refers to the total loss of pigment secondary to autoimmune effect (vitiligo) or congenital disorders (albinism)
- Consistency
- Feel of lesion may be helpful
Scales represent a proliferative disorder of epidermal cell turnover

Etiology

Papulosquamous:
- Infections:
  - Viral or bacterial
  - Rickettsial or fungal
- Allergic reactions
- Autoimmune disorders
Purpura and petechiae:
- Clotting or platelet disorder
- Vascular fragility disease
- Vasculitis
- Overwhelming infection
Vesiculobullous:
- Infection
- Drug reaction
- Autoimmune disorder
Ulcer:
- Infection
- Vascular insufficiency

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