Clinical characteristics of 68 children with atypical hand, foot, and mouth disease caused by coxsackievirus A6: a single-center retrospective analysis.

Background: Hand, foot, and mouth disease (HFMD) caused by coxsackievirus A6 (CV-A6) has become prevalent in many parts of the world. It is commonly referred to as atypical HFMD which more likely to present as bullous lesions. Compared with traditional HFMD, its misdiagnosis rate is relatively high, which brings difficulties to clinical diagnosis. We retrospectively analyze the clinical characteristics of children with HFMD with bullous lesions caused by CV-A6. Methods: The study included 68 children with atypical HFMD caused by CV-A6 who were hospitalized from 2018 to 2020. Data of the children including age, sex, month of HFMD onset, the morphologies and distribution of rashes, the details of fever, the presence or absence of onychomadesis, and laboratory test results were analyzed and compared between an infant group (<1 year), a toddler group (1-<3 years), and a preschool group (3-<6 years). Results: Of the 68 children, 67 were younger than 5 years old, with a male to female ratio of 1.62:1. The disease peaked in the period from June to September. With 75.0% of the infant group had more than three kinds of rashes; 95.0% of the preschool group had rashes in more than five locations. These differences were statistically significant (P<0.05). All children had fever. The peak fever in the toddler group was lower (P=0.033). No critical cases were observed in any of the groups. Of the 61 children who were successfully followed up, 68.9% developed onychomadesis within 2-3 weeks. The proportion of cases with abnormal liver function was 83.3%, 41.7%, and 10.0% in the infant, toddler, and preschool groups (P<0.001). The proportion of cases with increased serum creatine kinase MB isoenzyme (CK-MB) were significantly higher in the toddler group (P<0.05). Conclusions: Atypical HFMD caused by CV-A6 infection usually occurred in children under 5 years old. The morphologies of the rashes in the infant group changed more, while the rashes in the preschool group was more widely distributed. The incidence of critical cases was low. More than half of the cases can develop onychomadesis in the recovery period. Organ damage was relatively mild in the preschool group.