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When Opaque Or Discolored Hallux Nails Fail Multiple Treatments

Tracey Vlahovic DPM

Have you had patients who have one hallux nail that is dystrophic or onycholytic, and the other nine are normal in appearance? Has that nail failed every therapy you have tried? Does it look just like onychomycosis? Is your patient frustrated? 

Your patient may have asymmetric gait nail unit syndrome or AGNUS. Zaias and colleagues have described this clinical entity in two publications.1,2 When I heard it presented at the Council for Nail Disorders meeting, I was intrigued and my mind raced through my patients who fit the description. 

We, more than most professions, understand the body is not symmetrical.  Certainly, feet are not built to be a carbon copy of each other. We have long known that faulty biomechanics can affect the nail. AGNUS combines the biomechanical aspect with the notion that the feet are not mirror images. AGNUS is simply defined as “dermatophyte fungus-negative abnormal nail as a result of toe friction in a closed shoe in patients with asymmetrical walking gait.”1,2

The syndrome begins with a unilateral hallux nail presentation but may eventually involve both halluces. Patients may also complain of back pain. Ultimately, these nails look onychomycotic but frequently have negative fungal cultures. With AGNUS, there is onycholysis distally, the patient may have hyperkeratosis at the tip of the toe and, as Zaias and colleagues describe it, an asymmetrical walking gait due to dysfunctional foot biomechanics (which they ascertained by looking at shoe wear patterns).1,2 The nails might look more opaque or discolored than the non-affected nails. The authors hypothesize that the friction of the shoe against the nail in a patient with an abnormal gait will lead to AGNUS. Therefore, part of their treatment regimen is to have the patient forgo closed toed shoes. 

Anecdotally, my patients who I felt fit this description improved in the summer months when they could wear open-toed shoes daily. However, all of those positive changes regressed once patients returned to close-toed shoes in the fall and winter months.

What is the optimal treatment biomechanically? Insoles? Deep toe box shoes? mesh or Lycra upper soles? Should the patient move to a climate where open toe shoes are a reality 12 months out of the year? I am sure some of my patients would love to receive a prescription stating that.

In all seriousness, this is a new way of looking at this type of nail presentation and should at least make you remember that not everything is onychomycosis. Do any of your patients fit the AGNUS description and how would you manage this? 

References

1. Zaias N, Rebell G, Casal G, Appel J. The asymmetric gait toenail unit sign. Skinmed. 2012;10(4):213-7.

2. Zaias N, Rebell G, Escovar S. Asymmetric gait nail unit syndrome: the most common worldwide toenail abnormality and onychomycosis. Skinmed. 2014;12(4):217-23.

Editor’s note: The answer to the November blog (https://www.podiatrytoday.com/blogged/what-lesion ) was: squamous cell carcinoma. 

 

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