When does onycholysis become a more permanent, irreversible problem? Sharing insights from clinical experience and relevant research, these authors discuss the phenomenon of the disappearing nail bed, including insights on the pathogenesis of the condition, key contributing factors and pertinent treatment pearls.
Disappearing nail bed is a diagnosis you have most likely never heard of but you see it in practice on almost a daily basis. It describes the entity in which long-standing onycholysis causes the nail bed to convert to digital skin, which ultimately results in nail plate shortening in comparison to the contralateral side due to lack of nail bed-nail plate attachment.1 The shortened nail will only grow so far distally and seem to stop, or it will abut the distal skin that becomes hypertrophied and deformed. Often, patients will complain of the lack of nail growth when comparing one foot to another and will relate pain at the distal tip of the toe where the nail meets the skin.
The nail may appear yellowish or white in color, or exhibit hyperkeratosis at the most distal edge. There might be a small bump or hypertrophy of the distal skin that deforms the distal tip of the toe. You may culture the nail but the culture results may come back as negative for fungal growth. However, you are confident visually that this is toenail onychomycosis. Before delving into this disorder, let us differentiate onycholysis from onychomycosis and discuss the pathophysiology behind it.
Understanding The Pathogenesis Of Onycholysis
Differentiating between onychomycotic and true onycholytic nail disorders is difficult for even the most seasoned practitioners. This can create issues when it comes to proper diagnosis and treatment plans. Having a strong understanding of the key characteristics of onychomycosis and onycholysis can help ensure proper identification of these nail disorders, and reduce the amount of misdiagnosed culture-negative nails that receive incorrect treatment.
Onycholysis, separation between the nail plate and nail bed, is an early sign of onychomycosis, but not all nails that present with onycholysis are mycotic. Nails that have onycholysis without an underlying dermatophyte infection will not resolve with the use of an oral or topical antifungal. In our experience, entertaining the wide-ranging differential diagnoses of onycholysis (such as onychomycosis, onychogryphosis, psoriatic nails, lichen planus-affected nails and trauma-induced pathology) and employing appropriate clinical laboratory testing are important to determine the source of onycholysis, and prevent the complication known as the disappearing nail bed.
From a microscopic perspective, the nail plate is made up of about 80 layers of keratinized flattened cells.2 There are three macroscopic layers that make up the nail plate: the dorsal layer, which is a few cells thick; an intermediate layer, which is the most flexible and thickest layer; and lastly, the ventral layer, which is only one or two cells thick.2 The nail matrix and nail bed comprise the layers beneath the nail plate. One can visualize the nail matrix proximally as a “half-moon” shape or lunula in some nails (the hallux more so than the fifth digit). The nail matrix creates the nail plate.2
The nail bed begins from the distal edge of the lunula and extends all the way to the hyponychium distally. The nail bed lacks the keratin proteins K1 and K10 that are common in normal skin, and there is no granular layer like in the epidermis of normal or non-nail bed skin.2 The distal portion of the nail bed may have a different color in comparison to the rest of the nail bed and is usually a one to 1.5 mm transverse band of a deeper pink or brown.3 This is called the onychodermal band and is the first barrier present to prevent materials reaching underneath the nail plate.3
When there is a disturbance of the onychodermal band, a separation of the nail plate from the underlying nail bed may occur and this is known as onycholysis.4-7 Onycholysis typically originates at the distal free border of the nail plate and advances proximally. When onycholysis is present, the unattached nail plate will have a white appearance, whether it is in a linear streaking pattern or a geographic-like pattern.4-7 In the case of a dermatophyte invasion, the nail may present with yellow discoloration distally. If the onycholysis is present for an unknown period, the nail bed will become keratinized and develop dermatoglyphics, which ultimately results in what we know as the disappearing nail bed.4-7
Daniel and colleagues proposed a grading of onycholysis as follows:
• Stage one: early, initial separation of one to two mm of the distal nail plate from the hyponychium;
• Stage two: separation of the distal one-third of the nail plate;
• Stage three: separation of one- to two-thirds of the nail plate;
• Stage four: onycholysis extending from the proximal nail fold (onychomadesis) to the distal end of the nail; and
• Stage five: disappearing nail bed.8
Disruption of the onychodermal band can occur through a variety of events including but not limited to: idiopathic, which includes trauma, allergies, and contact irritants; psoriasis; trauma; drugs; onychomycosis; bacterial infections; and iatrogenic events (repeated nail surgery or total nail avulsion).9
Women present with onycholysis more commonly than men and it develops more commonly in adulthood. However, onycholysis can appear at any age.9 It is also more common in the great toenail but can be present in any nail. Onycholysis usually presents as asymptomatic and the patient may view it as a cosmetic concern.9 If one does not remove the aggravating factor causing the onycholysis, the longer the aggravating factor is present, the higher the probability that the nail plate may never reattach to the nail bed.1,9 Once the nail bed epithelializes, it cannot be reversed so timely treatment should occur before this nail diagnosis presents.
Pinpointing The Etiology Of Onycholysis
Treating the underlying cause of onycholysis is imperative to prevent a progression to disappearing nail bed or manage the already present disappearing nail bed.
Baran and Badillet reviewed 113 cases of onycholysis of the toenails.10 Even though some of the nails had bacteria and yeast-like organisms in onycholytic spaces, the authors could not rule out that the organisms caused the onycholysis. When pathological organisms reside in the onycholytic space, it is difficult to determine if the onycholysis came before the invading organism or was instead an effect of its presence. This can cause a dilemma when deciding on a proper treatment plan.
Baran and Badillet stated that if an invading organism caused the onycholysis, then treatment should include antifungals or antibacterial agents (such as in a Pseudomonas infection) to eliminate the pathogenic organism in hopes of restoring the nail bed.10 However, if there is no invading organism present, then treating the onycholysis should be the primary concern. For simple onycholysis caused by chronic and repetitive trauma, Baran and Badillet noted that proper foot balancing with insoles and proper shoe gear can prevent future traumatic events from continuously hitting the nail.10 Personally, the senior author sees this in patients who wear steel-toed boots for work and patients who have hallux extensus.
Essential Treatment Considerations For Onycholysis And The Disappearing Nail Bed
For the cases of disappearing nail bed that the senior author sees daily, she approaches it systematically and conservatively at first. When faced with a nail affected by disappearing nail bed and after obtaining an appropriate medical history, the clinician may order a radiograph collimated to the affected digit to rule out a subungual exostosis of the distal phalanx as the source for the deformed distal tip of the toe.
Also, appropriate nail diagnostic testing, such as periodic acid-Schiff (PAS) staining, fungal culture, etc., is appropriate to rule out onychomycosis as the source for the onycholysis. If a dermatophyte infection is present, appropriate antifungal therapy is warranted. Antifungal therapy will not cause reversal of the disappearing nail bed so it is important to ensure the patient has realistic expectations.
If the nail is ingrown at the distal tip, nail debridement can relieve discomfort. For patients who do not have a subungual exostosis as the underlying cause, the senior author teaches the patient to tape his or her toe with athletic tape or a Band-Aid®, starting from where the nail meets the skin distally, down and around the plantar pulp of the toe (see photos on page 29). This method encourages the skin to flatten in order for the nail to grow over the skin. Again, this will not cause adhesion of the epithelialized nail bed to the nail plate but has the potential to allow the nail to grow to a more desirable length since the hypertrophied distal skin will be flatter. The senior author suggests the patient performs this on a daily or nightly basis for a minimum of four hours.
For cases in which a subungual exostosis is present, one can perform an exostectomy of the distal phalanx with a skin plasty as needed to remove the excess skin at the tip of the digit. This skin plasty allows for the skin to lay flat in order for the nail to grow distally uninterrupted. The patient must be aware that this procedure does not restore the nail bed and there will be a cavern (i.e. continual onycholysis) under the nail plate, which will create the appearance of nail discoloration and be a possible invasion point for microorganisms.
There is another suggested surgical option for the disappearing nail bed but it is not a practical solution from a podiatric perspective. If there is a matrix still present underneath the problematic nail, Fernandez-Mejia and coworkers suggest a technique using a one to two cm mucosal graft from the hard palate.11 These authors recommend working in
conjunction with an otolaryngologist to assist with obtaining the graft. Afterward, the podiatric surgeon removes the nail’s unattached distal nail plate and proceeds to excise the nail bed down to the phalanx. The surgeon then places graft obtained from the hard palate in the offending area and sutures it down to the surrounding area. Fernandez-Mejia and colleagues noted that all six patients in their study showed 70 to 90 percent improvement in nail dystrophy, which they characterized by nail adherence to the nail plate.11
For nails that develop onycholysis due to an underlying inflammatory disease state like psoriasis or lichen planus, one may consider other topical or systemic conservative modalities. In a 2013 study, Park and colleagues found topical calcipotriol/betamethasone to be an appropriate treatment for nails in onycholysis stage one or two.12 However, the authors did not indicate differentiation of the nails from simple onycholysis in comparison to other pathologic onycholysis.13 Ultimately, if there is identification of the underlying disorder causing the onycholysis, the practitioner should treat that underlying diagnosis with the appropriate therapy.
Long-standing onycholysis can have irreversible physiologic consequences on the nail unit. Once epithelialization of the nail bed occurs, there is nothing short of a complex interdisciplinary surgical procedure to change it. There are no studies to determine how long onycholysis needs to be present for disappearing nail bed to occur. It may or may not be associated with onychomycosis, so proper clinical lab studies are necessary to rule out a dermatophyte infection.14 Overall, appropriate diagnosis is essential at the first signs of onycholysis in order to encourage nail bed reattachment to the nail plate and stop the progression to a disappearing nail bed.
Dr. Vlahovic is a Clinical Professor in the Department of Podiatric Medicine at the Temple University School of Podiatric Medicine in Philadelphia.
Dr. Borrelli is Chief Resident of the Podiatric Residency Program at CarePoint Health Hoboken University Medical Center in Hoboken, N.J.
Dr. Bruno is a third-year podiatric resident at Eastern Virginia Medical School in Virginia Beach, Va.
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