Article : Rash Decisions: Atypical Exanthems...

Rash Decisions: Atypical Exanthems in 260 Consecutive Patients

Awareness of morphologic pattern and of seasonal viruses may help with a difficult diagnosis.


An atypical exanthema (AE) is defined as an eruptive rash morphologically different from the six classical exanthems (measles, scarlet fever, rubella, erythema infectiosum, exanthem subitum, and chicken pox). Although AEs are common, they are diagnostically challenging, and not well studied. To characterize the clinical features and laboratory findings that might help establish the etiology of AEs, investigators studied 260 consecutive patients (108 children, 141 females) with AE who presented to a university dermatology department in Italy. Erythema multiforme patients were excluded.

Seven morphologic patterns emerged: erythema, erythema with macules, erythema with papules, erythema with vesicles, erythema with papules and petechiae, erythema with pustules, and urticaria. Morphologic patterns in adults and children were similar, though the pustular pattern occurred only in adults. Acute generalized exanthematous pustulosis (AGEP) was diagnosed in four cases.

Etiology was established in 201 cases (77%): 94 were viral; 38, bacterial; 65, drug-related; 3 due to parasites; and 1 combined cause. An infectious etiology was seen in 70% of childhood and 39% of adult cases. Viral infection was determined serologically. Petechial and erythematous-vesicular patterns; location on the buttocks, hands and feet, or face; and incidence in the spring and summer were associated with an infectious etiology, usually viral. Antibiotics and nonsteroidal anti-inflammatory drugs were the most common agents in drug-related exanthems. Routine laboratory investigations were not helpful except for anti-streptolysin O in streptococcal infections, and liver function tests in hepatitis A, Epstein-Barr, and cytomegalovirus infections. In 11 patients with biopsies, histology was nonspecific and only helpful for diagnosing AGEP.


Citation(s):

Drago F et al. The challenge of diagnosing atypical exanthems: A clinico-laboratory study. J Am Acad Dermatol 2012 May 22; [e-pub ahead of print].

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