Atypical hand, foot and mouth disease in adults associated with coxsackievirus A6: a clinico-pathologic study

BackgroundHand, foot, and mouth disease (HFMD) is a contagious illness most commonly occurring in children 5 years old or younger. The most common cause of HFMD in the United States is Coxsackievirus A16. HFMD is uncommon in adults, and may show other atypical features including a broader spectrum of cutaneous involvement and a greater degree of severity. MethodsWe evaluated the clinical, histopathologic and molecular features of three cases of atypical HFMD occurring in adults. ResultsAll three cases showed clinical features that were worrisome for erythema multiforme or a disseminated herpesvirus infection. The histopathologic findings were quite uniform, and showed intraepidermal vesiculation with a predominantly neutrophil-rich infiltrate. A characteristic feature was the specific involvement of the upper stratum spinosum and stratum granulosum, with relative sparing of the stratum corneum. In none of the cases was there evidence of herpesvirus. Molecular analysis performed on two of the cases showed involvement by Coxsackievirus A6, an uncommon serotype in HFMD. All three cases resolved spontaneously. ConclusionsAtypical HFMD associated with Coxsackievirus A6 represents an uncommon and potentially diagnostically challenging cutaneous eruption. Its recognition is critical to avoid unneeded therapy and to establish accurate prognostic expectations.