Seasonal occurrence, the presence of an enanthem and morphological patterns helped physicians to make etiological diagnoses of atypical exanthems in a recent study.
Researchers in Italy collected data for 260 consecutive patients (108 children and 152 adults), aged 9 months to 71 years, with atypical exanthems. The patients (141 females) were classified as having one of the following morphological patterns: erythema, erythema with papules, macules with papules, erythema with vesicles, macules with papules and petechiae, erythema with pustules, or urtircarial.
The exanthems had been present for fewer than 5 days in 189 patients (73%) at presentation, and enanthems were observed in 69 patients (26%), and divided almost evenly between adults and children. Among these patients, 57 had viral infections; four had bacterial infections.
Researchers found a causal relationship in 201 patients (77%), with 94 cases attributed to viruses, 38 to bacteria, 65 to drugs, three to parasites and one to viruses and drugs.
The researchers also found a relationship between morphological pattern and etiology. The morphological patterns of infectious exanthems had significant differences from those of unknown causes (gloves-and-socks syndrome x2=19.245; P=.02). The erythematous-vesicular pattern significantly indicated an infectious exanthem for children (x2=16.451; P<.001) and adults (x2=82.989; P<.001).
Exanthems and the seasons also were associated. In winter, when drug intake is more frequent, iatrogenic etiology (x2=4.041; P=.044) was prevalent, while infectious etiology, particularly viral infection, was more common during the spring/summer (x2=10.32; P=.0013). Bacterial infection showed a prevalence in the fall/winter (x2=10.771; P=.001).
The researchers noted patients whose hands and feet (x2=7.14; P=.006) and patients whose buttocks (x2=17.24; P<.0001) were affected by exanthems had enanthems more often than patients with involvement at other sites.
“Understanding the etiology of atypical exanthems remains difficult and often the routine procedures do not allow a definitive prognosis to be achieved,” the researchers said. “This study … provides some diagnostic clues to help determine the etiology of atypical exanthems.”