Case 2: A curious case of nail dystrophy: Is there a fungus among us?

A three-year, eight-month-old boy was referred by a consultant pediatrician for management of a presumptive diagnosis of onychomycosis following an eight-week history of fingernail and toenail dystrophy. One month before the onset of nail changes, he had experienced an episode of hand, foot and mouth disease (HFMD). There was no history of nailbed trauma or associated pain, and he was not taking any medications. His history was significant for autism spectrum disorder and an allergy to egg white. The family history was unremarkable. On physical examination, he was a well-appearing child in no apparent distress with only postinflammatory changes on the dorsum of the feet where he had been affected by HFMD. He had longitudinal horizontal bands over the thumbnails and the toenails (Figure 1). There was no interdigital scale and no other pathological skin changes were noted. Longitudinal depressed bands over the toenails of the right foot HFMD is a common viral infection mainly affecting young children. It is characterized by fever, sore throat, general malaise, and vesicular eruptions on the oral mucosa, tongue, hands, feet, buttocks and, less commonly, genitalia. HFMD is caused by different strains of enteroviruses, and small epidemics occur during the summer and autumn months. Nail dystrophies, such as Beau's lines and onychomadesis, have been associated with HFMD. Onychomadesis is the spontaneous, complete shedding of the nail from its proximal edge, without pain or inflammation, following temporary nail matrix arrest. Beau's lines, defined as the transverse ridging of the nail plate, is caused by a temporary slowing of nail matrix production. Severe Beau's lines can occur with HFMD, leading to an eventual shedding of the nails. Causes of onychomadesis include local trauma, periungual inflammation (eg, periungual dermatitis, paronychia), systemic medications (eg, retinoids, chemotherapy agents), pemphigus and Kawasaki disease. The lack of onycholysis, subungual debris and concominant tinea pedis help to distinguish onychomadesis from onychomycosis. There has been an increasing number of cases of HFMD-associated onychomadesis occurring in children, with latency periods ranging from four to 10 weeks postinfection. The first association of onychomadesis with HFMD was reported in 2000 in Chicago, Illinois, USA (1). There have since been numerous reports of this association globally, in Spain, Finland, Italy, France, Belgium, Japan and Taiwan. A case-control study in Valencia, Spain in 2008 involving 221 cases (214 children, 96% <6 years of age) established a clear link between HFMD and onychomadesis (OR 5.836; P<0.001) (2). The etiological agent responsible for onychomadesis after HFMD has included several serotypes of enteroviruses including coxsackieviruses A5, A6, A10, A16, B1 and B3; echoviruses 3, 4 and 9; and enterovirus 71. Patients with coxsackie A6 infection were also found to experience more severe symptoms such as desquamation and nail deformities. It is not known whether onychomadesis occurs due to direct inflammation of the periungual skin, a systemic impact of HFMD on children or a coxsackievirus-specific dysfunction of the nails, and there have been limited studies performed to investigate causative mechanisms. With HFMD-associated onychomadesis, the nails will eventually grow back, and treatment is not required. However, its recognition is important to avoid unnecessary investigations and treatment. Onychomadesis presents as complete shedding of the nail from its proximal edge. HFMD is a common and under-recognized trigger of onychomadesis. Onychomadesis from HFMD is self-resolving and usually presents four to 10 weeks after the onset of HFMD, with spontaneous regrowth of nails.

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