A Systematic Review of Median Nail Dystrophy: Clinical Presentation,Associated Risk Factors,and Management Outcomes

To the Editor,

Median canaliform nail dystrophy (MCND) is a rare benign nail disorder characterized by a central longitudinal split with an inverted fir-tree pattern, commonly found on the thumbnails.^1,2 The most common hypothesis involves repetitive trauma to the proximal nail fold and nail matrix, either self-inflicted or occupationally related, as well as compression by subungual tumors.^1,3 Familial inheritance and cases associated with isotretinoin therapy have also been reported; however, the cause is most often idiopathic. ¹ Management relies mainly on identifying and managing risk factors and various topical treatments.^1,2 To date, no systematic review has summarized the available literature on MCND.

To better evaluate the clinical features, associated risk factors, and treatment outcomes of MCND, we conducted a systematic review following PRISMA guidelines (Supplementary Figure 1). The protocol was registered in PROSPERO (CRD420251081213). A search of PubMed, MEDLINE, Embase, and Web of Science was performed from inception to June 19, yielding 331 unique records. In total, 44 case reports met the inclusion criteria, encompassing 57 patients (Supplementary Table 1).

Demographic data were available for 56 patients. The mean age was 34.18 ± 20.38 years (range: 2-87), of which 38 (67%) were males. Bilateral presentation was seen in most cases, 32 (56%), and unilateral presentation was documented in 13 (22%) patients. The most involved digits were the thumbs, 36 (53%). Predisposing or risk factors were divided into categories, including 28 (49%) idiopathic cases, 18 (32%) behavioral and trauma-related, 10 (18%) medication-related mostly due to systemic retinoids, 4 (7%) atopic dermatitis cases, either as a direct cause of nail changes or an underlying condition leading to repetitive trauma, 1 (2%) familial, and 1 (2%) iatrogenic.

Treatment of MCND is pursued to address cosmetic concerns associated with this condition. In most cases, management was primarily through addressing the identified risk factors or likely underlying cause, in addition to adjunct off-label treatments. These included, topical tacrolimus (n = 10, 18%); behavioral modification, including psychiatric consultation, cognitive-behavioral therapy, and structured plans to reduce nail trauma in device use (n = 9, 16%); completion, discontinuation, or reduced dosage of isotretinoin or alitretinoin (n = 6, 11%); topical steroids (n = 6, 11%); biotin or multivitamins (n = 5, 9%); and topical or foam tazarotene (n = 4, 7%).

In most cases, adjustment of systemic retinoid therapy led to complete resolution and regrowth of healthy nails. Behavioral modification was also effective in most patients achieving complete resolution. Multivitamin supplementation was variably effective, with 3 cases achieving complete resolution and 2 showing improvement. Topical tazarotene resulted in near-complete or complete resolution in 2 cases, suggesting modest efficacy in selected patients.

Our findings highlight the diverse clinical presentation and multifactorial etiology of MCND. Treatment outcomes suggest that addressing the underlying cause is often effective. However, the evidence is limited by small sample sizes, inconsistent outcome reporting, and heterogeneity in study designs and underlying etiologies. These factors limit the generalizability of findings and preclude firm conclusions. Further studies are needed to evaluate treatment efficacy and guide optimal management strategies.