Diagnostic Approach to Rash in Young Adults

Questions and Answers

Morphology of the lesion

An initial lesion that has not been altered by trauma or manipulation, and has not regressed

A circumscribed, elevated lesion that measures ≥ 1 cm and contains serous or hemorrhagic fluid

Primary lesion is the initial lesion, secondary lesion develops as the disease evolves Signup and view all the answers

Global reaction pattern Signup and view all the answers

A circumscribed, nonpalpable discolouration of the skin that measures ≥ 0.3 cm Signup and view all the answers

A circumscribed, elevated lesion that measures < 1 cm and contains serous fluid Signup and view all the answers

Morphology of the lesion, global reaction pattern, distribution of lesions Signup and view all the answers

An inflammatory skin eruption Signup and view all the answers

Study Notes

A rash is an inflammatory skin eruption.
Differential diagnosis of a rash is primarily based on the morphology of the lesion.

Primary lesion: the initial lesion that has not been altered by trauma or manipulation and has not regressed.
Secondary lesion: develops as the disease evolves or as the patient damages the lesion (e.g., rubbing, scratching, infections).

Bulla: a circumscribed, elevated lesion that measures ≥ 1 cm and contains serous or hemorrhagic fluid (i.e., a large blister).
Macule: a circumscribed, nonpalpable discoloration of the skin that measures ≤ 0.3 cm.
Pustule: a lesion that contains pus; may be follicular (centered around a hair follicle) or nonfollicular.
Vesicle: a circumscribed, elevated lesion that measures < 1 cm.

Identify the primary lesion, which is the typical element of the eruption.
Determine the global reaction pattern.
Note the distribution of the lesions (e.g., diffuse, isolated, localized, regional, universal).