Proposing an Algorithm to Treat Dystrophic Toenails

Nail pathology can be an indication of systemic underlying disease, but also can have etiologies including biomechanical abnormalities, psoriasis, fungal infection, physiological disturbances, deficiencies in vitamins and minerals, or a secondary bacterial infection. Half of the nail disease seen in the office is onychomycosis.¹ Other issues that can present uniquely in the toenails include disappearing nail bed, onychogryphosis, onychomadesis, and retronychia.

All of these entities fall under the umbrella of the term “nail dystrophy” that can be visually similar to onychomycosis. This article will review various nail maladies and present an algorithm to assist the practitioner in the office.  

A Guide To Nail Disease States

Onychomycosis. Onychomycosis or tinea unguium is caused by invasion of the nail unit by dermatophytes, non-dermatophyte molds, and/or Candida albicans. Onychomycotic nails generally are described as onycholytic, discolored, and hyperkeratotic with subungual debris.¹ Clinicians may see concomitant tinea pedis or tinea cruris in patients with onychomycosis.

The most common form of onychomycosis on the toenails is distal lateral subungual onychomycosis caused by Trichophyton rubrum. Clinically, it may be difficult to distinguish onychomycosis from other existing nail pathologies such as nail psoriasis. KOH prepration, periodic acid-Schiff (PAS) staining, polymerase chain reaction (PCR) testing, and fungal culture can aid in determining the presence of a dermatophyte-caused infection.

Treatment for onychomycosis includes targeting the causative organism with either oral terbinafine, oral itraconazole (typically in pulsed doses), oral fluconazole dispensed in once weekly dosages, oral griseofulvin ultramicrosize, topical ciclopirox 8% solution, topical tavaborole 5% solution, and topical efinaconazole 10% solution. Mechanical debridement to debulk the nail unit is standard to create comfort in shoes.  

Differential diagnoses of a mycotic nail include psoriasis, trauma, and biomechanically induced nail dystrophy. Often due to shoe gear, the fifth toenail becomes dystrophic and thickened. Patients and practitioners alike will confuse this with onychomycosis. If one sees this with concomitant onychomycosis and treats the patient systemically, the practitioner should discuss with the patient the possibility that the fifth toenail may not respond to treatment. The underlying cause of the dystrophy can be biomechanical (adductovarus fifth toe) or tight-fitting shoes. A Lister’s corn or focal hyperkeratotic lesion that may appear to the patient as a “split nail” lateral to the nail plate may also be present.  

Onychauxis, onycholysis, and discoloration secondary to trauma in a severely contracted hammertoe may frustrate the patient who is pursuing antifungal therapy and questioning why a treatment regimen is not successful. In these cases, it is imperative to educate the patient about the biomechanical cause of the nail thickening and the treatment options which range from purchasing a shoe with a deeper toe box to decrease pressure to surgical management of the digital deformity, if warranted.  

Psoriasis. Psoriasis can affect the skin, nails and joints. Classically, psoriatic nail disease consists of: onycholysis; salmon (oil) spots (discolored areas that represent nail bed psoriasis); an irregular pitting pattern; and onychauxis. Koebner phenomenon, or the appearance of lesions at the site of injury, can also occur in the nails and may manifest in an asymmetrical presentation. If a patient presents with an onychomycosis-like nail involvement and has failed oral antifungals, one should consider a diagnosis of psoriatic nail disease. Also, if psoriatic plaques and nail dystrophy are present, it does not automatically lead to a diagnosis of psoriatic nail disease.¹ Confirmatory lab testing (PAS, PCR, etc.) is essential to achieve the correct diagnosis. In addition to the nail changes, periungual erythema may be present. Patients may also present with the arthritic component of psoriasis, which may manifest in dactylitis of the digits (sausage toes), enthesitis of the Achilles tendon, and distal interphalangeal joint involvement.  

Management of nail psoriasis involves reducing the inflammatory response. Treatments include: injection of corticosteroid (such as triamcinolone) into the nail matrix, use of topical tazarotene, oral acitretin, or some of the systemic biologic agents.  

Lichen planus of the nail. Lichen planus is an idiopathic T cell–mediated inflammatory condition, which affects the skin, hair, nails, and mucous membranes. This condition more commonly affects fingernails but, in my practice, I have found toenail disease related to lichen planus to be more common than the literature describes.¹

Lichen planus usually affects several nails. The nails become thin, rough (trachyonychia), ridged longitudinally (onychorrhexis), fissured, and can develop a dorsal wing formation of the proximal nail fold (or pterygium formation) over the nail plate. If the matrix damage from lichen planus is not addressed, these nail findings become permanent scarred reminders of the skin disease that may resolve. Clinicians may manage nail lichen planus with injectable steroids like triamcinolone into the nail matrix.  

What You Should Know About Other Signs of Nail Dystrophy

Beau’s lines. Beau’s lines are transverse palpable grooves that run along the nail and represent periods of arrest in growth of the nail plate. The growth arrest is attributed to prior severe systemic illness or trauma.² Each insult to the nail matrix is eventually followed by recovery and continuation of nail growth.³ This generates the grooved appearance of the nail.³

Beau’s lines most commonly occur bilaterally, affecting all 20 digits, as a result of systemic illnesses and drugs. In some cases, it can occur in isolation when trauma or isolated digital inflammation is involved, specifically trauma to the hand, wrist, elbow, or foot. These traumas can include manicures, pedicures, shoe trauma, as well as fractures to the hand, wrist, or elbow.⁴ Some more common systemic conditions linked to Beau’s lines are zinc deficiency, erythroderma, psoriasis, eczema, pemphigus, Raynaud’s disease, hyperpyrexia, acute stress, rheumatic fever, malaria, myocardial infarction, oral retinoid treatment, and chemotherapy treatment.^4–6 Considering that fingernails grow at a rate of about 0.1mm per day and toenails about 0.03mm per day, the length of time of the pathology can be gauged by measuring the distance from the proximal nail fold to the distal groove of the Beau’s line.^4,5  

During a pedicure, the process of manipulating the cuticle may lead to Beau’s lines, or depressions of the nail plate that are parallel to the proximal nail fold. Also, scraping of the hyponychium can lead to onycholysis, which provides a pocket for dermatophyte infection to take hold.  

Onychorrhexis. Onychorrhexis is described as nail thickening and ridging in a longitudinal pattern. Nails with onychorrhexis have a coarse appearance and can be casually described as “brittle nail syndrome.”⁷ Features of onychorrhexis can vary from a small number of isolated ridges to deep involvement covering up to 70% of the nail. Longitudinal splitting can be superficial or deep.⁸ Twenty percent of people have reported signs of brittle nails. Women are more frequently affected, and the incidence is 15% higher in patients over 60 years old.⁸

Onychorrhexis is most commonly caused by trauma from exogenous sources, lichen planus, and systemic pathologies. All causes are related to disorganized regulation of keratin in the nail matrix.⁹ Exogenous traumas such as chemical exposure, frequent hand washing, and pedicures are among the more common causes.⁹

Furthermore, onychorrhexis is a hallmark feature of lichen planus. Diagnosis of lichen planus can be inferred from a large midline indentation or ridging, but this finding can be normal in elderly patients.⁷

Systemic findings include anemia and arteriosclerosis, which decreases the oxygen content of the matrix and leads to keratin disorganization.¹⁰ Other metabolic causes include rheumatoid arthritis, hyperthyroidism, hypothyroidism, anorexia nervosa, bulimia nervosa, and Raynaud’s disease.^9–11 It has been theorized that sulfur content is diminished in patients with onychorrhexis. This leads to fewer disulfide bonds in proteins that form keratin fibrils.¹⁰ Treatment of onychorrhexis is dependent on the underlying source of the problem.

Leukonychia. Leukonychia describes the white discoloration of the nail plate and presents clinically as leukonychia totalis, leukonychia partialis, leukonychia striata, and leukonychia punctata.¹² Leukonychia totalis involves whiteness of the entire nail and has commonly been described as a hereditary condition that is autosomal dominant.¹³ Leukonychia partialis involves only a portion of the nail and is more commonly associated with a systemic disease or trauma. However, both conditions can be acquired or inherited.¹⁴ While the exact pathophysiologic mechanism of leukonychia totalis is unclear, it is thought to be due to abnormal keratinization of the nail plate.¹⁵

While leukonychia can be associated with several disease states and toxicities, some common ones include renal disease, liver disease, cardiac disease, and arsenic intoxication.¹⁶ When associated with these disease states it will often present as one of four nail patterns, these being Mee’s lines, Terry’s nails, half-and-half (or Lindsay’s nails), and Muehrcke’s lines.¹⁶

Mee’s lines are transverse, non-blanching, non-palpable, white bands that run parallel to the lunula.¹⁷ These lines are associated with arsenic poisoning, certain chemotherapeutic drugs, and Hodgkin’s lymphoma.¹⁷

Terry’s nails involve whiteness of almost the entire nail with a sparing of the distal 0.5–3.0mm and it is indistinguishable from the lunula.¹⁸ This pattern can occur with congestive cardiac failure, chronic renal failure, hepatic disease, diabetes, and idiopathically.¹⁸

Lindsay’s nails present with the proximal one-third to one-half of the nail being white with the distal aspect being reddish-brown.¹⁹ This arrangement is seen in patients with chronic kidney disease and renal failure.¹⁹

Muehrcke’s lines are multiple white parallel bands that are separated by normal pink tissue and are present on all nails bilaterally.²⁰ These lines are characteristic in individuals who have chronic hypoalbuminemia associated with hepatic disease and cirrhosis.²⁰ For these disease-associated manifestations of leukonychia, correction of the underlying disease may lead to normalization of the nails.²¹

Longitudinal melanonychia (LM). Longitudinal melanonychia (LM) presents as a brown/black longitudinal band that extends from the nail matrix to the distal edge of the nail plate.²² LM is caused by one of two processes, either melanocytic activation or melanocyte proliferation.²³ Most longitudinal melanonychia is caused by a benign process like melanocytic activation or melanocytic nevi; however, another cause is malignant melanoma.²³ Nail melanomas are most commonly seen between ages 50 and 60 and should be examined further if LM presents during this time period.²² Age, along with factors such as the lesion being greater than 6mm, location (the thumb, great toe, and index finger are most common), and skin color require more in-depth examination.²² If LM is present on one digit, perform further examination as there is a higher incidence of malignancy.²² Performing an in-depth and thorough patient history is the first step in diagnosing malignant or benign LM. Medication, and social and medical history can indicate trauma or drug use as the cause and rule out malignancy.  

A helpful tool in diagnosing whether LM is malignant or benign is the dermatoscope. Dermatoscopy allows the visualization of lesions that are not normally seen and will reduce the number of unnecessary biopsies for patients with LM. Dermatoscopy has a few limitations as it cannot visualize the nail matrix where the disease begins.²⁴ For this reason, nail biopsies are the gold standard to determine benign vs. malignant LM. Many different techniques can be performed; however, it is important to obtain the nail matrix specimen as this is where the nail grows from, and where the disease begins.

If the lesion is benign LM, the course of action for these patients is reassurance and periodic evaluation. However, if found to be malignant, surgical excision is indicated.²⁵ Treatment includes the excision of 5–10mm borders with or without bone resection and possible lymph node resection. More aggressive treatment requires amputation at the appropriate joint level.²²

An Algorithm for Nail Evaluation: Targeted to Expanded

Podiatric physicians are faced with unique factors causing toenail dystrophy. The following algorithm aims to assist the clinician in the office when faced with a nail that may not have a fungal infection. Ultimately, I recommend focusing on the nail itself and then expanding out to identify any pedal issues followed by any systemic causes that could be creating nail dystrophy.  

1. Assess the nail unit characteristics. How many nails are dystrophic? Is it symmetrical or bilateral? What is the shape of the nail? Does the nail “stop” growing due to the shape of the distal digit like in a disappearing nail bed? What color(s) are present (red, black, green, yellow, brown, white)? What is the quality of the nail plate: brittle, peeling, dry? Is the cuticle present? What is the quality of the periungual skin (scaly, erythematous, pruritic)? How does the nail plate and bed appear when viewed distally instead of looking down on it? Are there Beau’s lines, onychorrhexis, or pigmentation present?

2. Assess the anatomy and any underlying biomechanical issues. Anatomically, what is present that could be affecting the nails? Hammertoes, hallux valgus, hallux limitus/rigidus, long second toe, adductovarus fifth toe? Is there a correlation between the nail issue and the anatomy and/or biomechanics?

3. Assess for an internal or an external cause. Is there a history of trauma, inflammatory skin disease (psoriasis, eczema, etc.), or chemotherapeutic agents that may contribute to nail issues (onychocryptosis to pigmentation changes). Does the patient get pedicures regularly, including gel nail polish or application of acrylic nails? Has the patient had numerous nail surgeries over the years that has narrowed the nail plate widthwise? Or has the patient had repeated total nail avulsions that has caused the nail bed to disappear? Does the patient “pick” their nails and periungual skin?  

4. Perform lab testing or a biopsy of the nail unit. Once the above questions have been assessed, laboratory nail testing may be performed to refine the diagnosis. This may involve PAS staining, PCR testing, KOH/fungal culture, or a punch biopsy of the nail unit. A simple punch biopsy of the nail unit can be used to identify the cause of LM, nail psoriasis, proximal subungual onychomycosis, various skin cancers affecting the nail, subungual verrucae, and other nail tumors.  

5. Formulate a treatment plan. Treatment options will depend on the results of the lab testing or clinical assessment. If shoe gear is an issue, then a discussion on proper shoe size, depth, and type may be warranted. Surgical intervention of either the nail unit or anatomical issue (ie, adductovarus fifth toe) may be appropriate. See above for therapeutic options for nail involvement in inflammatory skin conditions. The following section describes over-the-counter options for onychodystrophy of various causes.  

Non-prescription Treatment Options: Devices, Cosmetic, and Nutritional

Onychodystrophic nails are typically dry in appearance. A topical product that has been on the over-the-counter market for several years is DermaNail (Summers Labs). It is described as a nail conditioner for brittle nails and is applied topically daily.  

In addition, if cosmesis is a concern for the patient, Keryflex^™ (Podiatree) nail resin may be applied to camouflage and protect the nail unit. Keryflex^™ has been used to cover nail fungus and various other nail dystrophies.  

I no longer recommend biotin supplements due to the US Food and Drug Administration’s (FDA’s) statement on possible interference with lab testing.²⁶ It significantly interferes with laboratory studies, causing either a falsely high or low result depending on the test.²⁶ Biotin (or vitamin B7) is used in laboratory studies due to its ability to bind to specific proteins. For example, biotin is a part of the lab test for detection of troponin T, a marker of cardiac damage.²⁶ Both patients and physicians may be unaware of the potential biotin interference in lab tests.

Patients may not even realize that their “hair, skin and nails” supplement they bought at the drugstore contains higher than recommended doses of biotin or has biotin at all. If your patient is taking biotin supplements, make them aware that many lab tests, including but not limited to cardiovascular diagnostic tests and hormone tests that use biotin technology, are potentially affected, and incorrect test results may be generated if there is biotin in the patient’s specimen.²⁶

Final Thoughts

Nail pathology is a staple condition evaluated by podiatrists daily. However, the multitude of potential etiologies, especially those that originate outside the foot itself, make clear work-up and treatment a necessity. Familiarizing oneself with the key points and questions outlined in this proposed algorithm is the first step in optimizing outcomes for these patients.

Dr. Vlahovic is a Clinical Professor at Temple University School of Podiatric Medicine in Philadelphia. She discloses she is a consultant for Ortho Dermatologics and Bako Diagnostics.

References

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