The Venetian antithesis: Treating median canaliform nail dystrophy
By Warren R. Heymann, MD, FAAD
Oct. 4, 2023
Vol. 5, No. 40
Tony Bennett may have left his heart in San Francisco, but mine remains in Venice. (The editorial staff of DWI&I offer our sincerest condolences to the families of those who perished, and our prayers for recovery of those injured, in the tragic bus accident yesterday in Venice.) My wife and I first visited this splendiferous city of 120 islands, 177 canals, and 391 bridges 40 years ago, having returned twice — each time with undiminished awe. It is not the magnificence of St. Mark’s square or the Rialto Bridge over the Grand Canal that beckons my return, but rather the enchantment of getting lost in the labyrinth of the footbridges over the canals, with each island offering its charm. Climate changes hastening Venice’s demise by causing rising sea levels, in concert with the fact that the city is sinking due to its pile foundation being pushed down vertically into mud, is frightful. Hopefully, the soon-to-be-completed Mose (Experimental Electromechanical Module) project will be helpful; a long-term solution may require following the model of the Delta project of dams and dikes operating in the Netherlands. (1)
The canals dermatologists confront are on the nails in the condition known as median canaliform nail dystrophy (MCND, aka MCND of Heller, median nail dystrophy [MND], or solenonychia). Clinicians need to differentiate MND from other disorders that may cause linear defects of the nail, especially the habit tic deformity. It is easier to differentiate other disorders that may display linear nail defects such as subungual tumors, digital mucous cysts, lichen planus, lichen striatus, Darier disease, and others. (2,3)
MCND of Heller is characterized by a midline or a paramedian ridge or split and canal formation in the nail plate of one or both the thumbnails. The first case was reported by Heller in 1928. Men and women are affected equally. The mean age of occurrence is 25.72 years. The condition is diagnosed based on its clinical features. (3) Classically, the thumbs are involved, although other fingers and even the great toenails may be affected. The appearance has been likened to an “Inverted fir tree” because of the midline longitudinal furrow with multiple transverse parallel lines. (4) In contrast, habit-tic deformity is characterized by multiple transverse ridges, lacking the longitudinal splitting observed in MCND. Wang et al note that both conditions may coexist, as observed in a 58-year-old man with habitual cuticle manipulation due to pruritus from his atopic dermatitis. The authors suggested that these disorders may have a similar pathogenesis and be on the same disease spectrum. (5)
Aside from those cases where trauma to the proximal nail fold and matrix is evident, the etiology of MCND is obscure. A temporary defect of the nail matrix has been presumed, be it due to microtrauma (including nail biting, pruritus), infection, tumor, or drugs such as oral retinoids (isotretinoin, aliretinoin), and ritonavir. (6) Damevska et al reported a case of MCND in an 11-year-old girl following cryosurgery for periungual warts; spontaneous resolution occurred. (7) Familial cases of MCND have been reviewed by Sweeney et al. (8) Although the inheritance pattern was not defined, my read of the article suggests an autosomal dominant mode of transmission. A histopathologic analysis is not usually performed and is not very informative; parakeratosis and melanin in the nail bed keratinocytes may be observed. (3)
Although MCND can spontaneously remit, it is usually long-standing and recalcitrant to therapy. If due to obsessive manipulation of the digit, behavioral/psychiatric intervention may be warranted. For those cases where the etiology is unknown, anecdotal reports include a litany of therapies: topical steroids, intralesional steroids (9), topical tacrolimus (10), dupilumab (11), marigold (6), PUVA, and the Nd:YAG laser. (9) Tucking the thumb into the palm, until the urge to manipulate the nail passes, may help. (12) What inspired me to write this commentary was the excellent response to tazarotene foam within 5 months in a 33-year-old woman with MCND (see image). (13) (I know that I should not get too excited by a solitary case report; however, I have never successfully treated MCND with anything I have prescribed — at least this gives me hope!) To date there are no reports in PubMed focusing on JAK inhibition for MCND, but you know they’re coming! Devoted dermatologists will continue to work hard to eliminate dystrophic nail canals. To avoid the ravages of climate change, Venetians are actively devoting their energy and intellect for solutions to maintain their canals and magnificent city. I pray for their success.
Point to Remember: Median canaliform nail dystrophy is easy to recognize but difficult to treat. Recent reports utilizing tazarotene foam, dupilumab, and marigold offer some promise that warrant further study with appropriate trials.
Our expert’s viewpoint
Matilde Iorizzo, MD PhD FMH
Private Dermatology Practice, Bellinzona/Lugano, Switzerland
European Nail Society vice president, Swiss Hair & Nail Group coordinator
When dealing with longitudinal nail splitting running all or part of the length of the nail plate, a distinction should be made between post traumatic cases (20%) with a clear history of trauma versus those due to tumors (45%) or inflammatory disorders (25%). Congenital and systemic diseases are also possible causes but are less frequent. Among the congenital causes, the median canaliform dystrophy of Heller is most distinctive. Although familial cases have been recorded, most are sporadic and do not have a known cause.
Literature about this topic is sometimes misleading because median canaliform dystrophy of Heller is often misdiagnosed with midline transverse ridging of habit tic (aka washboard nails) therefore, data on its prevalence and incidence may not always reliable. In median canaliform dystrophy the nail plate, the split is usually in the midline, with a fir tree-like appearance of ridges angled posteriorly. The thumbs are most commonly affected, and the involvement may be symmetrical. The cuticle is usually normal, and this is a sign that should help in the distinction from washboard nails where the cuticle is pushed back by a repetitive and unconscious habit tic using another finger (usually the 2nd digit is used to push back the cuticle of the thumb).
As stated, median canaliform dystrophy is usually bilateral affecting both thumbs. If diagnosed as unilateral, a tumour should always be ruled out. Almost one third of tumours producing nail plate splitting are, in fact, malignant and it is common for nail unit tumours to affect the thumb.
Median canaliform dystrophy is a long-standing condition — after a period of months or years the nails can return to normal, but relapse may always occur. It is often a bothersome condition and patients seek a remedy, however literature on potential treatments is scant and the dystrophy is often recalcitrant to therapy.
Potential benefits due to tazarotene are not surprising as retinoids accelerate both nail growth and desquamative effects as well as normalizing keratinocyte differentiation.
Delivery of topical drugs is always difficult, especially in the matrix area. It is often only mildly effective and can be time-consuming. That said, clinicians are often reluctant to prescribe systemic treatments when the disease is localized to the nails. For a disease limited to one fingernail, prescription of a topical product is more than justified — even the known tazarotene side effect of irritation of the nail folds is a risk worth taking compared to the results. Due to the slow growth rate of the nail plate and the difficulty for the active drug to penetrate the nail tissues, it is necessary to wait several months before seeing improvement so follow-up should be in 4-6 months.
Surely more patients should be treated, maybe with a split hand (non-dominant hand) study, to draw definitive conclusions about the success of a treatment.
Phelan J. Venice is at risk of succumbing to its sinking foundations and rising sea levels. To avert disaster, the city is making changes. Future Planet. September 27, 2022. https://www.bbc.com/future/article/20220927-italys-plan-to-save-venice-from-sinking
Khodaee M, Kelley N, Newman S. Median nail dystrophy. CMAJ. 2020 Dec 14;192(50):E1810. doi: 10.1503/cmaj.201002. PMID: 33318093; PMCID: PMC7759106.
Kota R, Pilani A, Nair PA. Median Nail Dystrophy Involving the Thumb Nail. Indian J Dermatol. 2016 Jan-Feb;61(1):120. doi: 10.4103/0019-5154.174092. PMID: 26955129; PMCID: PMC4763640.
Pathania V. Median Canaliform Dystrophy of Heller occurring on thumb and great toe nails. Med J Armed Forces India. 2016 Apr;72(2):178-9. doi: 10.1016/j.mjafi.2015.06.020. Epub 2015 Aug 31. PMID: 27257330; PMCID: PMC4878880.
Wang C, Lee S, Howard A, Foley P. Coexisting median canaliform nail dystrophy and habit-tic deformity in a patient with atopic dermatitis. Australas J Dermatol. 2020 Feb;61(1):e100-e101. doi: 10.1111/ajd.13084. Epub 2019 Jun 3. PMID: 31155700.
Wilson A, Tariq Khan M, Murrell DF. Median canaliform nail dystrophy in a 2-year-old boy: Case report and review of the literature. Pediatr Dermatol. 2022 Nov 13. doi: 10.1111/pde.15181. Epub ahead of print. PMID: 36372450.
Damevska K, Duma S, Pollozhani N. Median canaliform dystrophy of Heller after cryotherapy. Pediatr Dermatol. 2017 Nov;34(6):726-727. doi: 10.1111/pde.13257. Epub 2017 Aug 29. PMID: 28851117.
Sweeney SA, Cohen PR, Schulze KE, Nelson BR. Familial median canaliform nail dystrophy. Cutis. 2005 Mar;75(3):161-5. PMID: 15839359.
Choi JY, Seo HM, Kim WS. Median canaliform nail dystrophy treated with a 1064-nm quasi-long pulsed Nd:YAG laser. J Cosmet Laser Ther. 2017 Aug;19(4):225-226. doi: 10.1080/14764172.2017.1279330. Epub 2017 Jan 31. PMID: 28135887.
Kim BY, Jin SP, Won CH, Cho S. Treatment of median canaliform nail dystrophy with topical 0.1% tacrolimus ointment. J Dermatol. 2010 Jun;37(6):573-4. doi: 10.1111/j.1346-8138.2009.00769.x. PMID: 20536678.
Giura MT, Viola R, Dika E, Ribero S, Ortoncelli M. Median canaliform nail dystrophy of Heller in a patient with atopic dermatitis: 'miraculous' healing with dupilumab. Clin Exp Dermatol. 2020 Jul;45(5):601-602. doi: 10.1111/ced.14169. Epub 2020 Jan 29. PMID: 31889326.
Jiang J, Kern JS, Tam M. A simple solution for habit-tic nail deformity. Australas J Dermatol. 2023 Aug;64(3):e295-e296. doi: 10.1111/ajd.14077. Epub 2023 May 17. PMID: 37195687.
Quan EY, Johnson NM. Successful treatment of median canaliform nail dystrophy with topical tazarotene foam. JAAD Case Rep. 2022 Sep 7;29:70-71. doi: 10.1016/j.jdcr.2022.08.051. PMID: 36204694; PMCID: PMC9529541.
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