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Athlete's Puzzling Toe Ailment

Editor's Note: The Case Challenge series includes difficult-to-diagnose conditions, some of which are not frequently encountered by most clinicians, but are nonetheless important to accurately recognize. Test your diagnostic and treatment skills using the following patient scenario and corresponding questions. If you have a case that you would like to suggest for a future Case Challenge, please email us at ccsuggestions@ with the subject line "Case Challenge Suggestion." We look forward to hearing from you. Background and Initial Presentation A 36-year-old woman presents to the clinic with a longstanding nail complaint (1-2 years' duration). She is otherwise healthy and reports aching pain and tenderness surrounding her right great toenail that has been worsening over the last year. The immediate proximal skin of the toe has signs of inflammation and redness. The surrounding tissue is not draining fluid or bleeding. The toenail itself has yellow discoloration and a thickened appearance with a pattern similar to that of an oyster shell. She notes that her nail appears to grow in horizontal layers but seems to have stopped growing over time. She no longer feels the need to clip its end. She reports discomfort during exercise and periods of walking or running. All her other toenails and fingernails are unaffected. She denies any personal or family history of nail issues or psoriasis. She regularly hikes and goes for long runs and has worn the same brand of running shoes for many years. She wears shoes of "medium" width and Converse brand shoes when lifting weights. She says that these shoes sometimes feel tight-fitting and often apply pressure to her toes while exercising. Her pain, tenderness, and swelling of the proximal nailfold began around 1-2 years ago and have gradually become more bothersome. She also reports that she began noticing abnormal-appearing nail growth several months before the initial onset of symptoms. She cannot recall any specific major traumatic incident involving the nail around that time. Another healthcare provider, who presumed a case of onychomycosis (toenail fungus), had prescribed a topical antifungal treatment to use twice daily. She had also tried other topical therapies, including an antibiotic ointment and petroleum jelly, in addition to a course of oral antibiotics. None of these treatments significantly improved her condition. She is most bothered by the discomfort she feels while doing physical activity, as she is an avid runner and hiker. Physical Examination and Workup A thorough physical examination using a dermatoscope revealed xanthonychia (yellowing of the nail), along with a thickened longitudinal curvature (Figure 1) and marked onycholysis (separation of the nail plate from the nail bed). Paronychia (inflammation) and erythema (redness) of the proximal nail fold were also observed. The cuticle appeared to be absent. These signs suggest an issue that interferes with proper nail growth and indicates that infection, trauma, or irritation to the periungual tissues has occurred. No visible signs of infection were observed on clinical examination. A nail clipping for dermatopathology was also performed to rule out fungal involvement, since a previous healthcare provider had not performed laboratory work but rather treated empirically with a topical antifungal. Dermatopathology results were negative for fungal involvement. Retronychia is typically diagnosed based on clinical examination and dermoscopy, which reveal features such as proximal paronychia, a thickened and layered nail plate, onycholysis, and an absent cuticle. The diagnosis is supported by a thorough patient history and may be confirmed by excluding similar conditions such as onychomycosis or nail psoriasis through nail clipping and dermatopathologic analysis. Retronychia can also be diagnosed based on ultrasonography if more than two overlapping nail plates are present, blood flow is increased through the dermis of the proximal nailbed and posterior nailfold, the distance between the nail plate's origin and the base of the distal phalanx is decreased, and echogenicity is decreased.[1,2] While rarely performed in everyday practice, ultrasonography is a noninvasive examination that allows for clear visualization of the nail and underlying tissue.[1,3] This can help to rule out potential tumors and other possible complications. It is particularly useful for observing clinical changes consistent with nail psoriasis.[4] Conventional radiography can be used in the initial investigation for bone and joint deformities or bony outgrowths associated with trauma or suspected tumors. However, other imaging modalities (eg, ultrasonography) would be more appropriate for this patient.[5] Retronychia is an underreported and underdiagnosed condition in dermatology. Case studies in research and literature are limited. Symptoms of retronychia can mimic other more commonly recognized nail disorders involving inflammation of the proximal nailfold. Individuals with retronychia may endure a prolonged duration of symptoms before seeking treatment, which can further confound the clinical diagnosis. While retronychia primarily affects adults, it can occur in all ages.[6] It is more common in women than in men, partially owing to the choice and fit of footwear. Shoes with narrow toe boxes limit the forefoot's range of motion and predispose feet to loading stress. Women tend to wear shoes with longer lengths to compensate for the lack of width or depth that their feet need, in addition to wearing shoes with elevated heels more regularly than men. This can exacerbate foot pathology and pain, such as corns and calluses, as well as nail disorders like retronychia.[7] Pathophysiology of Retronychia Retronychia is a chronic inflammatory condition characterized by ingrowth of the proximal nail plate toward the proximal nailfold.[8] Retronychia results from misaligned nail growth and multiple generations of nail plate localization beneath the initially damaged nail.[1] When the toe experiences repetitive microtrauma or a major traumatic event, the growing nail loses support from the nailbed but remains adhered laterally to the nail matrix or abnormally to the distal nail bed, forcing continued misalignment between the nail plate and nail matrix. Newly growing nail plates become embedded in the proximal nail fold, and old nail plates are unable to be properly shed.[3] The nail unit thus remains unstable and susceptible to further microtrauma, which perpetuates the cycle of nail plate layering.[9] Figure 1. Retronychia of the great toenail, seen on the right (patient's left toe). The nail surface appeared in a horizontal layered pattern, likely an indication of generations of nail being repetitively pushed backward into the nail matrix and causing the nail to "stack" in layers. In retronychia, the old nail plate becomes misaligned with the nail matrix, preventing it from becoming pushed out as new nail plates grow. Distal onycholysis perpetuates the cycle of nail dystrophy by reducing the surface area of the anchored nail, which can lead to gradual longitudinal shortening of the nail bed.[10] The nail thus becomes continuously destabilized from the matrix and more prone to backward displacement with trauma. In long-term retronychia, the formation of a distal bulge can manifest as another consequence of continuous backward pressure on the nail and often contributes to the progression, maintenance, and relapse of retronychia (Figure 2).[1,8] Granulation tissue may form under the proximal nailfold, particularly in more advanced cases.[2] The cuticle often appears to be absent, and proximal nail fold inflammation and erythema are frequently observed. > Figure 2. The vast majority of retronychia cases result from trauma (isolated incident or repetitive microtraumas) and ill-fitting footwear.[1] Regular physical activity is another underlying factor observed in many cases. Ischemic etiologies that contribute to nail dystrophy may also be linked to retronychia by precipitating disrupted nail matrix growth. Some conditions hypothesized to fall under this category are compartment syndrome and thrombophlebitis.[11] Furthermore, individuals with static disorders of the foot may be predisposed to retronychia.[11] Congenital malalignment of the great toenail (lateral deviation of the nail plate), reflex compensatory hyperextension of the halluces, and an Egyptian foot type (characterized by a longer great toe and shorter second toe) are podiatric conditions that can increase stress on the great toe and make it more susceptible to trauma. They also seem to be encountered more often in practice than they are reported.[11] Potential hereditary factors and static disorders of the feet should therefore be accounted for in the management of retronychia to prevent relapse. Retronychia may cause varying symptom severity, affecting motivation to seek treatment. The earlier the diagnosis is made, the less likely recurrence will occur and the higher success rate treatment interventions will yield. Differential Diagnoses Retronychia can often be mistaken for onychomycosis, as both conditions share similar manifestations of yellowing discoloration and thickening of the nail plate.[12] Onychomycosis is common, constituting 40%-50% of all nail disorders, making clinicians more likely to mistake retronychia for onychomycosis in its early stages.[13] Since no fungus was detected in the tested sample, antifungal therapies would be ineffective in treating this patient's condition. Collecting a nail clipping for dermatopathology, in conjunction with dermoscopy, can also be helpful in ruling out nail psoriasis, another common misdiagnosis of retronychia. Nail psoriasis is frequently characterized by pitting of the nails, onycholysis, red spots in the lunula, subungual hyperkeratosis (which can also be seen in retronychia), and oil or salmon patches.[13] Nail psoriasis more often affects the fingernails, whereas retronychia primarily affects the toenails — particularly the great toenails. Retronychia can also manifest similarly to onychomadesis or Beau lines.[10] Both nail dystrophies involve a disruption to nail growth following some type of insult to the nail matrix. Beau lines appear as parallel ridges or grooves across the nail plate due to slowed nail plate production. Onychomadesis, a more severe form of Beau lines, is the proximal separation of the nail plate from the nailbed associated with cessation of nail plate growth from the matrix.[14] Drugs, specifically chemotherapeutic agents, are one of the most common causes of Beau lines, while infections are a more common cause of onychomadesis.[14] Both onychomadesis and retronychia are linked to chronic repeated trauma. In onychomadesis, however, the old nail plate separates from the nail bed but remains aligned with the nail matrix, allowing the new nail plate to gradually push out and replace the old one. The prognosis is usually promising.[15] Onychorrhexis is characterized by longitudinal ridging or splitting of the nail plate due to fragility, often seen in conditions such as lichen planus, aging, nutritional deficiencies, or systemic disease. Retronychia typically affects one or both great toenails and is far less common in other toes or fingernails.[15] The great toes are more susceptible because of their exposure to repeated trauma from bearing body weight and experiencing continuous pressure during walking, standing, or exercising. Early stages of retronychia are characterized by cessation of nail growth, xanthonychia, and mild acute paronychia with associated pain. Late stages involve the classic layered nail plate, along with onycholysis of the distal nail and subungual hyperkeratosis (buildup of keratin under the nails).[1] Purulent discharge is not seen in retronychia. It suggests an infectious etiology. The patient in this case experienced mild pain and discomfort that gradually worsened over time. In some cases of chronic retronychia, however, pain may be minimal or entirely absent.[9] Treatment for retronychia depends on the severity of symptoms at the time of diagnosis and the patient's motivation to treat. Conservative treatment methods involve high-potency corticosteroids in topical (eg, clobetasol propionate) or intralesional (eg, triamcinolone acetonide) preparations. These can be used to target paronychia in the proximal nailfold for mild-to-moderate cases.[15] Intralesional corticosteroid injections show promising results, with one study showing a definitive cure in 27 of 28 patients in an "intermediate stage" of retronychia after three rounds of once-monthly triamcinolone acetonide injections.[6] A third steroid injection was warranted in only 4 of 28 of patients. Nail plate discoloration, proximal nail fold discharge, and nail elevation significantly improved after just one session, and cessation of nail growth improved after the second. Other conservative treatment options include consistent taping to alleviate some pressure and promote regular nail growth. Additionally, wrapping the affected toe in a protective foam tube may lessen further microtrauma and prevent relapse of symptoms.[8] Recurrence is always a risk with conservative treatment. Nonconservative treatment entails surgical intervention — specifically proximal or complete nail plate avulsion. Superimposed nail plates can be removed, and granulation tissue can be excised with this method.[11] This remains the treatment of choice for chronic or end-stage cases of retronychia that do not respond well to conservative treatments. Patients undergoing this procedure should experience pain relief and prompt healing, and the new nail plate is expected to grow back normally (Figure 3). Mild postoperative nail dystrophy is a risk, but it is rare.[11] Examples include retraction of the nail bed with pincer nail, hypertrophy of periungual tissues, and micronychia.[2] In cases with severe pain or nailfold hypertrophy, nail surgery can be performed with the DuBois (for mild-to-moderate cases) or super "U" (for severe cases) techniques to reduce excess periungual tissue.[2,6] While these procedures are more invasive and require better analgesic control, complication and recurrence rates appear to be low.[16] Patients who decline surgery may be treated with a chemical avulsion instead, using a 50% urea occlusive dressing overnight to promote softening of the nail.[2,3] Figure 3. A patient with retronychia pre- (left) and post- (right) complete surgical nail avulsion. Regardless of the treatment used, retronychia can persist even with minimal trauma to the foot. Static disorders of the foot, if present, should be corrected to minimize predisposition to trauma. For long-term management of symptoms, it is critical for patients to wear open-toed shoes or close-toed shoes with an adequate toe box to permit ample space for movement and decreased pressure on the toenails. Medical or surgical intervention will be more effective if properly fitted footwear is also incorporated. The patient in this case should consider having her feet sized and begin wearing wide-width shoes, if warranted. She should also seek shoe brands that advertise wider toe boxes. Over the long term, nonconstrictive footwear will help to reduce loading pressure on the toes, enhance stability of the feet, and prevent future trauma to the involved nail plate and matrix.[9] The prognosis for this patient, if treated appropriately, is slow nail regrowth with minimal long-term deformity. Complete resolution without treatment is improbable because of the chronic inflammatory nature of retronychia, which can lead to persistent discomfort and complications if unaddressed. Permanent nail loss is also unlikely, as the new nail plate is typically expected to grow back normally. Finally, rapid onset of pain requiring immediate surgical intervention is not characteristic of retronychia; this patient's pain developed gradually, and conservative treatments are often the initial approach for mild-to-moderate cases, with surgery reserved for more advanced or unresponsive cases. The prognosis of retronychia can vary widely based on the severity and duration of symptoms, as well as the treatment approach used. Mild cases can be managed conservatively. In moderate-to-severe cases, regular nail regrowth will most likely be restored through surgical nail avulsion. Regardless of the chosen treatment, patients need to be educated on properly fitted footwear with generous toe space, as this accounts for a significant risk factor of progression and recurrence. If detected early and managed effectively through appropriate treatment methods in conjunction with addressing the original triggering factor(s), positive outcomes can be expected. Retronychia is largely underreported and underrepresented in current literature. Provisional diagnoses may be confusing, and symptoms may be overlooked by the patient and/or healthcare provider, especially if they are mild or nonspecific. It is important for clinicians to be familiar with distinct indicators of this disease to avoid unnecessary treatments and promote optimal health outcomes.