A while back I was reading an interesting article from the dermatologist, Dr Eckhart Haneke entitled “Double nail of the little toe” (1) . The paper describes a retrospective review of Dr Haneke’s patients over a 13-year period, documenting what he labelled as “double nail of the fifth toe”. On looking at the images provided of selected cases, it became apparent that these lesions, in podiatric parlance could in fact be a Durlacher’s corn (also known as Lister’s corn in North America).
Figure 1 : Examples of a double nail: Image courtesy of Dr E Haneke (1)
A strange name for a corn perhaps but it takes its name from British chiropodial royalty. The Durlacher family were a family consisting of four generations of chiropodists (Solomon Abraham 1757-1845), Lewis (1792-1864), Alexander (1822-????), Montague (1824-1894) and Edward [nee Newton Jones] who adopted the name by marriage to Montague’s daughter). The term “Durlacher corn” was coined after probably appearing in the text by Lewis Durlacher (first published in 1845) – “Treatise on Corns, Bunions, the Diseases of Nails, and the general Management of the Feet" (2). In it he says “The corn which is seated close to the nail is acutely painful, and to the unaccustomed eye difficult to discover, being long and thin in its form and concealed under the pellicle near the root. This species of corn more frequently attacks young people, as soon as they commence wearing stout shoes, which are usually made more pointed than the foot, so that the pressure is thrown exactly on the outer angle of the toe.”
Figure 2 : Examples of a double nail: Image courtesy of Dr E Haneke (1)
The implication from reading this is that the lesion is hyperkeratotic skin, similar other types of corn. In practice, we frequently come across corns on the fifth toes. Most commonly on the lateral side of the proximal interphalangeal joint related to shoe wear or close (but not associated the nail unit - figure 3) . Corn-like lesions closely associated with the base of the nail are treated by podiatrists enucleating these painful lesions.
Figure 3 : Corn (close but not associated with the nail unit)
After reading the paper by Dr Haneke, it is thought provoking – are Durlacher’s corns in fact another miniature section of nail? Dr Haneke believes so and that they represent part of a double nail. He describes 58 cases from practice where he identifies cases of “double nail”. Described as a normal nail. Sometimes slightly wide but close examination with the dermatoscope demonstrates a nail in two parts often separated by a longitudinal depression or split. In addition, he describes how many had callus associated lateral to the nail – often misdiagnosed as a corn. In his patient cohort, the majority were bilateral. Patients reported pain in about 20% of cases. The main method of treatment described in the paper was a partial nail avulsion to remove the smaller, lateral section of the nail, only when the lesion was painful for patients. Results from histological specimens excised from patients demonstrated the removed sections were in fact nail not skin, adding evidence to the theory.
Speaking to Dr Haneke, he believes most “Durlacher” corns to be miniature nail sections on the lateral edge. Also, in a few cases where he was able to obtain a decent radiograph of the distal aspect of the fifth digit (very tricky), often a “Y” shaped phalanx could be seen. The phalanx shape ultimately dictates the nail shape so such a deformity may give rise to a double nail.
References
1. Haneke E. Double Nail of the Little Toe. Skin Appendage Disorders. 2015;1(4):163-7.
2. Durlacher L. A concise treatise on corns, bunions and the disorders of the nails, with advice for the general management of the feet. London: Simpkin, Marshall and Co.,; 1858.