The patient with an acute maculopapular rash presents a diagnostic challenge to the clinician. The term maculopapular is somewhat non-specific, as many eruptions have a primary morphology of macules or papules, and the term may be mis-used to indicate any rash. The term rash is itself also non-specific and is sometimes incorrectly applied to any skin finding; eruption may be preferred for a cutaneous reaction of acute onset. However, the term maculopapular rash is in common clinical usage and will be retained here for purposes of simplicity. Synonyms for maculopapular rash include exanthematous eruption (exanthem) or morbilliform eruption.
The term maculopapular rash typically implies an acute and generalised eruption.
A brief review of morphological terms is appropriate.
Macule: a flat skin lesion <1 cm in greatest diameter. When macules exceed 1 cm, the appropriate term is patch.
Papule: a raised bump <1 cm in diameter. When papules exceed 1 cm in size, the appropriate term is plaque (palpable lesions elevated above the skin surface) or nodule (a larger, firm papule with a significant vertical dimension).
Other morphological terms encountered in this clinical setting include:
Pustule: a papule containing purulent fluid
Vesicle: a papule containing clear serous fluid
Bulla: a larger vesicle >1 cm
Urticaria: a wheal or hive.
Hence, the term maculopapular rash implies a skin eruption of flat and raised lesions.
Initial considerations in evaluating the maculopapular rash include the morphology, duration, and distribution. Age, gender, family history, medicines, known allergies, and exposures are also of primary importance.
Lesions are typically erythematous or reddened, due to the presence of inflammation.
Commonly, the eruption in a given patient is a combination of macules, papules, patches, plaques, and even other morphologies, though one morphology may predominate.
Age may be the single most important predictive factor of diagnosis. In the absence of other data, maculopapular rash in adults is most likely to be drug related, while maculopapular rash in children is most likely to be viral related.
The duration of the eruption may be acute (recent onset, <4 weeks), sub-acute (4-8 weeks), or chronic (>8 weeks). These timeframes are arbitrary.
An acute eruption often has a specific trigger, such as an allergic (e.g., medicine) or infectious (e.g., viral) exposure. The distribution of the eruption can be localised or generalised.
Other clinical factors, including the presence of fever, headache, and other signs of illness, are of great importance. Some conditions with a serious clinical course have a maculopapular eruption as a presenting sign and evaluation should be carried out urgently.
The primary differential diagnoses to consider for a maculopapular rash are:
Bacterial infections (including those that are toxin mediated)
Systemic diseases (e.g., acute graft-versus-host disease and Kawasaki disease)
Generally, a maculopapular eruption in the absence of fever or systemic systems is not urgent. When fever or signs of illness are present, urgent illness must be considered. Several conditions with serious clinical course may have a maculopapular eruption as a component, and evaluation should be carried out urgently if suspected. Among them are:
Toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS)
Drug reaction with eosinophilia and systemic symptoms (DRESS)
Staphylococcal scalded skin syndrome (SSSS) and toxic shock syndrome (TSS)
Rickettsial spotted fever.
MN declares that he has no competing interests.
Dr Mark Naftanel would like to gratefully acknowledge Dr Hobart W. Walling, a previous contributor to this monograph. HWW declares that he has no competing interests.
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