Eczema

Overview
  • Eczema is a type of dermatitis characterized by prototypical gross and histological morphological features as well as particular clinical findings. A variety of etiologies can lead to eczematous rashes although in many cases no particular cause is found.
Morphology
  • Overview
    • The gross and histological morphology of eczema classically evolves between acute, subacute, and chronic timescales. Some of this evolution is likely due to chronic itching and rubbing which occurs in response to the pruritis that is characteristic of eczematous eruptions. However, as described under the etiology section below, certain eczematous etiologies have unique morphological features.
  • Acute Eczema
    • Acute eczematous eruptions typically manifest grossly as juicy erythematous papules and plaques and may display vesicles. Lesions may possess crust and scales as well. Histologically, this is characterized by spongiosis and a perivascular dermal lymphocytic infiltrate
  • Chronic Eczema
    • Over time, eczematous lesions become progressively lichenified, transforming into thickened plaques with accentuation of skin markings. There is matched by histological lichenification as well with epidermal acanthotic, hyperkeratotic and a continued dermal perivascular lymphocytic infiltrate.
Etiologies and Clinical Consequences
  • Overview
    • A variety of etiologies can result in eczematous eruptions and in many cases an idiopathic cause is identified after others have been ruled out. The common clinical theme of these causes is pruritis which can be quite severe in contact and atopic etiologies.
  • Contact Dermatitis
    • Contact Dermatitis can caused by the direct chemical irritant effect of a substance or an allergic immune response to topically applied antigens. A large variety of culprit substances exist including poison ivy or poison oak, cosmetics, nickel, rubber compounds, or even substances in topical medications. The major clue to contact dermatitis is the distribution of the lesion, which will classically follow the distribution of the applied substance. For example, poison oak dermatitis may display a distribution of linear streaks as a person brushes up against branches whereas dermatitis secondary to nickel will often be localized to the skin touching buttons or jewelry. Depending on the timescale of exposure contact dermatitis may display juicy papules, vesicles, and even bullae if acute, or lichenified plaques if exposure has been long-standing.
  • Atopic Dermatitis
    • Please refer to the Atopic Dermatitis page for an review of this particular etiopathogenesis.
  • Idiopathic Eczema
    • When a clear source for an eczematous eruption cannot be found an idiopathic cause is suspected. Once again, lesions typically evolve clinically and histologically over time through acute, subacute, and chronic stages.
Treatment
  • Dermatologists can use a wide variety of treatments for eczematous eruptions; however, topical corticosteroids are often the first choice. However, when contact dermatitis is to blame, the first therapeutic step is identification and elimination of all sources of the culprit substance