Shedding Light on Onychomadesis

Onychomadesis is an acute, noninflammatory, painless, proximal separation of the nail plate from the nail matrix. It occurs due to an abrupt stoppage of nail production by matrix cells, producing temporary cessation of nail growth with or without subsequent complete shedding of nails.^1-10 Onychomadesis has a wide spectrum of clinical presentations ranging from mild transverse ridges of the nail plate (Beau lines) to complete nail shedding.^4,11 Onychomadesis may be related to systemic and dermatologic diseases, drugs (eg, chemotherapeutic agents, anticonvulsants, lithium, retinoids), nail trauma, fever, or infection,⁵ and a connection between onychomadesis and hand-foot-and-mouth disease (HFMD) was first described by Clementz et al¹² following outbreaks in Europe, Asia, and the United States.

Epidemiology

Onychomadesis has been observed in children of all ages including neonates. Neonatal onychomadesis is thought to be related to perinatal stressors and birth trauma, with possible exacerbation by superimposed candidiasis.¹⁰ Depending on the underlying cause, there may be involvement of a single nail or multiple nails. Nag et al¹ noted that onychomadesis was most commonly observed in nails of the middle finger (73.7%), followed by the thumb (63.2%) and ring finger (52.6%). Fingernails are more commonly involved than toenails.¹

Clementz et al¹² first proposed the association between onychomadesis and HFMD in 2000. Patients with a history of HFMD were found to be 14 times more likely to develop onychomadesis (relative risk, 14; 95% confidence interval, 4.57-42.86).⁴ A common pathogen for HFMD is coxsackievirus A6 (CVA6),^13,14 but the mechanism of onychomadesis in HFMD remains unclear.^5,7,13 Outbreaks of HFMD have been reported in Spain, Finland, Japan, Thailand, the United States, Singapore, and China.¹⁵ During an outbreak of HFMD in Taiwan, the incidence of onychomadesis following CVA6 infection was 37% (48/130) compared to 5% (7/145) in cases with non-CVA6 causative strains.¹⁶ There also have been observed differences in the prevalence of onychomadesis by age: a 55% (18/33) occurrence rate was noted in the youngest age group (range, 9–23 months), 30% (8/27) in the middle age group (range, 24–32 months), and 4% (1/28) in the oldest age group (range, 33–42 months), with an average of 4 nails shed per case.¹⁷ A study in Spain also found a high occurrence of onychomadesis in a nursery setting, with 92% (11/12) of onychomadesis cases preceded by HFMD 2 months prior.¹⁸

Etiology

Local trauma to the nail bed is the most common cause of single-digit onychomadesis.⁴ Multiple-digit involvement suggests a systemic etiology such as fever, erythroderma, and Kawasaki disease; use of drugs (eg, chemotherapeutic agents, anticonvulsants, lithium, retinoids); and viral infections such as HFMD and varicella at the infantile age (Table).^5,9,19 Most drug-related nail changes are the outcome of acute toxicity to the proliferating nail matrix epithelium. If onychomadesis affects all nails at the same level, the patient’s history of medication use and other treatments taken 2 to 3 weeks prior to the appearance of the nail findings should be evaluated. Chemotherapeutic agents produce nail changes in a high proportion of patients, which often are related to drug dosage. These effects also are reproducible with re-administration of the drug.²⁰ Onychomadesis also has been reported as a possible side effect of anticonvulsants such as valproic acid (VPA).²¹ One study evaluating the link between VPA and onychomadesis indicated that nail changes may be due to a disturbance of zinc metabolism.²² However, the pathomechanism of onychomadesis associated with VPA treatment remains unclear.²¹ Onychomadesis also has developed after an allergic drug reaction to oral penicillin V after treatment of a sore throat in a 23-month-old child.²³

Nail involvement has been reported in 10% of cases of inflammatory conditions such as lichen planus²¹; however, it may be more common but underrecognized and underreported. Grover et al⁹ indicated that lichen planus–induced severe inflammation in the matrix of the nail unit leading to a temporary growth arrest was the possible mechanism leading to nail shedding. Prompt systemic and intramatricial steroid treatment of lichen planus is required to avoid potential scarring of the nail matrix and permanent damage.⁹

Onychomadesis also has been reported following varicella infection (chickenpox). Podder et al¹⁹ reported the case of a 7-year-old girl who had recovered from a varicella infection 5 weeks prior and presented with onychomadesis of the right index fingernail with all other fingernails and toenails appearing normal. Kocak and Koçak⁵ reported onychomadesis in 2 sisters with varicella infection. There are few reported cases, so it is still unclear whether varicella infection is an inciting factor.¹⁹

One of the most studied viral infections linked to onychomadesis is HFMD, which is a common viral infection that mostly affects children younger than 10 years.¹ The precise mechanism of onychomadesis for these viral infection events remains unclear.^7,10,13 Several theories have been delineated, including nail matrix arrest from fever occurring during HFMD.⁶ However, this cause is unlikely, as fevers are typically low grade and present only for a few hours.^4,6,13 Direct inflammation spreading from skin lesions of HFMD around the nails or maceration associated with finger blisters could cause onychomadesis.^1,5,7 Haneke²⁴ hypothesized that nail shedding may be the consequence of vesicles localized in the periungual tissue, but studies have shown incidence without prior lesions on the fingers and no relationship between nail matrix arrest and severity of HFMD.^5,6,13 Bettoli et al²⁵ reported that inflammation secondary to viral infection around the nail matrix might be induced directly by viruses or indirectly by virus-specific immunocomplexes and consequent distal embolism. Osterback et al¹⁴ used reverse transcription–polymerase chain reaction to detect CVA6 in fragmented nails from 2 children and 1 parent following an HFMD episode, suggesting that virus replication could damage the nail matrix, resulting in onychomadesis. Cabrerizo et al¹⁸ also suggested that virus replication directly damages the nail matrix based on the presence of CVA6 in shed nails. Because fingernails with onychomadesis are not always of the fingers affected by HFMD, an indirect effect of viral infection on the nail matrix is more plausible.⁸ Additional studies are needed to clarify the virus-associated mechanism of nail matrix arrest.⁶ Finally, frequent washing of hands¹⁵ resulting in maceration, Candida infection, and allergic contact dermatitis² may be possible causes. It is unclear if onychomadesis following HFMD is related to viral replication, inflammation, or intensive hygienic measures, and further investigation is needed.^2,15