Introduction: Subungual acantholytic dyskeratotic acanthoma is a rare benign tumor of epidermal keratinocytes characterized by acantholysis and dyskeratosis. Only 7 other cases have been published in the literature. Case Presentation: A 29-year-old male presented with painful erythronychia and onycholysis of the left thumbnail. He worked as an electrician and was ambidextrous. Two months prior to the onset, he reported completing a mechanical task which led to repeated and sustained pressure to his left thumb. The clinical diagnosis was onychopapilloma, and a longitudinal excision was performed to remove the tumor. However, on histopathological examination, the primary features were hyperkeratosis, acantholysis, and dyskeratosis, consistent with a final diagnosis of subungual acantholytic dyskeratotic acanthoma. Conclusion: Nail trauma was reported by our case as a preceding feature, and this has not been described previously. Pain may accompany nail changes in the presentation of this tumor. Although subungual acantholytic dyskeratotic acanthoma is a benign tumor, it caused disruption in productivity, and our case highlights the need for timely access to specialist nail services.

Established Facts

  • Subungual acantholytic dyskeratotic acanthoma is a rare benign nail tumor with only 7 other cases published in the literature.

  • Clinical presentation includes longitudinal erythronychia, xanthonychia, distal onycholysis, and subungual hyperkeratosis.

Novel Insights

  • Nail trauma may be an etiological factor and possibly be under-recognized.

  • Given the frequent involvement of the thumb, subungual acantholytic dyskeratotic acanthoma may adversely impact function and productivity, underscoring the need for timely assessment by specialist nail services.

Acantholytic dyskeratotic acanthoma (also sometimes referred to as acantholytic acanthoma or acantholytic dyskeratoma) is an uncommon benign tumor of epidermal keratinocytes. Subungual acantholytic dyskeratotic acanthoma is a rare variant with only 7 other published cases in the literature (shown in Table 1) [1‒5]. Histologically, it is characterized by acantholysis and dyskeratosis. In this report, we share a case of subungual acantholytic dyskeratotic acanthoma including its presentation, histopathology, and some novel features.

Table 1.

Summary of solitary nail lesions with subungual acantholysis and dyskeratosis [1‒5]

ReferenceAgeSexLocationClinical featuresHistological features
Isonokami and Higashi [3] (1990) 20 4th finger, right Painful, longitudinal, and subungual red streak with distal wedge-shaped subungual keratosis Suprabasal acantholysis leading to lacunae. Dyskeratosis forming corps ronds and grains 
Sass et al. [5] (2009) 53 Thumb, right Rapidly evolving subungual tumor with proximal erythronychia, xanthonychia, and distal splinter hemorrhages with warty appearance of tumor at the free edge Epidermal acanthosis and subungual hyperkeratosis. Suprabasal acantholytic clefts and dyskeratotic cells (corps ronds and grains) 
15 Thumb, right Asymptomatic longitudinal xanthonychia, distal erythronychia, and onycholysis 
12 Thumb, right Red macule of the lunula, longitudinal linear onycholysis 
Ng et al. [4] (2018) 25 Thumb, right Longitudinal erythronychia, distal onycholysis, hyperkeratotic plaque at the free edge Suprabasal acantholytic clefts and dyskeratotic cells (corps ronds and grains) 
Carlioz et al. [1] (2020) 55 Thumb, left Longitudinal leucoxanthonychia, few splinter hemorrhages, distal nail plate erosion, localized hyperkeratosis Numerous acantholytic and dyskeratotic cells, horizontal architecture, and ill-defined borders 
Wu et al. [2] (2023) 54 Thumb, right Painful longitudinal xanthonychia and distal wedge-shaped onycholysis Suprabasal acantholysis, the distal nail bed had foci of diffused acantholysis, and dyskeratosis 
Current case 29 Thumb, left Painful longitudinal erythronychia, subungual hyperkeratosis, and distal onycholysis Predominant hyperkeratosis and acantholysis. Dyskeratosis seen 
ReferenceAgeSexLocationClinical featuresHistological features
Isonokami and Higashi [3] (1990) 20 4th finger, right Painful, longitudinal, and subungual red streak with distal wedge-shaped subungual keratosis Suprabasal acantholysis leading to lacunae. Dyskeratosis forming corps ronds and grains 
Sass et al. [5] (2009) 53 Thumb, right Rapidly evolving subungual tumor with proximal erythronychia, xanthonychia, and distal splinter hemorrhages with warty appearance of tumor at the free edge Epidermal acanthosis and subungual hyperkeratosis. Suprabasal acantholytic clefts and dyskeratotic cells (corps ronds and grains) 
15 Thumb, right Asymptomatic longitudinal xanthonychia, distal erythronychia, and onycholysis 
12 Thumb, right Red macule of the lunula, longitudinal linear onycholysis 
Ng et al. [4] (2018) 25 Thumb, right Longitudinal erythronychia, distal onycholysis, hyperkeratotic plaque at the free edge Suprabasal acantholytic clefts and dyskeratotic cells (corps ronds and grains) 
Carlioz et al. [1] (2020) 55 Thumb, left Longitudinal leucoxanthonychia, few splinter hemorrhages, distal nail plate erosion, localized hyperkeratosis Numerous acantholytic and dyskeratotic cells, horizontal architecture, and ill-defined borders 
Wu et al. [2] (2023) 54 Thumb, right Painful longitudinal xanthonychia and distal wedge-shaped onycholysis Suprabasal acantholysis, the distal nail bed had foci of diffused acantholysis, and dyskeratosis 
Current case 29 Thumb, left Painful longitudinal erythronychia, subungual hyperkeratosis, and distal onycholysis Predominant hyperkeratosis and acantholysis. Dyskeratosis seen 

A 29-year-old male was referred to a sub-specialist nail clinic for an abnormality of the left thumbnail which was noted 6 months prior. Initially, the nail lesion was painless; however, after 3–4 months, the patient experienced localized pain with sporting activities (e.g., boxing) and cold weather.

He reported being ambidextrous and worked as an electrician. Two months prior to noticing the thumb lesion, he recalled performing a repetitive mechanical installation task resulting in sustained pressure to his left thumb. He had no other significant medical conditions.

On clinical and dermoscopic examination, there was a subungual lesion affecting the lateral left thumbnail with hemorrhage at the proximal nail fold, erythronychia, distal onycholysis, and subungual hyperkeratosis at the free edge (shown in Fig. 1). All other nails were normal. There were no clinical signs of other skin diseases. The preferred diagnosis prior to excision was onychopapilloma with a differential diagnosis of Bowen disease and warty dyskeratoma.

Fig. 1.

a–c Clinical and dermoscopic appearance at presentation: hemorrhage at proximal nail fold, erythronychia, distal onycholysis, and subungual hyperkeratosis at the free edge.

Fig. 1.

a–c Clinical and dermoscopic appearance at presentation: hemorrhage at proximal nail fold, erythronychia, distal onycholysis, and subungual hyperkeratosis at the free edge.

Close modal

A procedure was performed to remove the tumor. A digital nerve block at the base of the thumb with plain lignocaine 2% with additional infiltration at the proximal nail fold was administered. A lateral curled nail avulsion exposed the tumor. A longitudinal tangential excision of the nail bed and proximal matrix around the tumor was performed. The defect was closed directly with a 4–0 absorbable suture.

Histological sections showed nail matrix and bed, with underlying onychodermis. There was a thickened and partly papillomatous squamous lesion showing hyperkeratosis, mild hypergranulosis prominent acantholysis, and some dyskeratosis (shown in Fig. 2). No crateriform or cup-shaped hyperkeratosis was apparent. Classic corps ronds were absent. No significant nuclear atypia or inflammation was seen. No invasive carcinoma was seen.

Fig. 2.

a Histopathology, H&E, ×100: Thick hyperkeratosis, parakeratin, and squamous epithelium with acantholysis. b Histopathology, H&E, ×200: Markedly thickened squamous epithelium with acantholysis and dyskeratosis. c Histopathology, H&E, ×400: Thickened squamous epithelium showing acantholysis, disordered hypergranulosis, and dyskeratosis.

Fig. 2.

a Histopathology, H&E, ×100: Thick hyperkeratosis, parakeratin, and squamous epithelium with acantholysis. b Histopathology, H&E, ×200: Markedly thickened squamous epithelium with acantholysis and dyskeratosis. c Histopathology, H&E, ×400: Thickened squamous epithelium showing acantholysis, disordered hypergranulosis, and dyskeratosis.

Close modal

The first likely description of subungual acantholytic dyskeratotic acanthoma was published in 1990 as a case of “focal acantholytic dyskeratosis.” However, this was not recognized as a distinct entity at the time [3]. In 2009, a case series was presented by Sass et al. [5] of 3 patients with suspected onychopapilloma based on clinical features. However, histologically, all cases showed coexistence of acantholysis and dyskeratosis. Since 2009, 3 other cases have been described in the literature (shown in Table 1).

Shared clinical features of subungual acantholytic dyskeratotic acanthoma include longitudinal erythronychia, xanthonychia, distal onycholysis, and subungual hyperkeratosis. This appearance mimics onychopapilloma which is often the preferred clinical diagnosis prior to histological analysis.

Common clinical and dermoscopic features of onychopapilloma include a subungual hyperkeratotic mass, distal fissures, erythronychia, and longitudinal ridging [6]. Kim et al. [7] described lunula notching, macrolunula, and trailing lunula along the longitudinal band as previously undescribed but relatively common dermoscopic features of onychopapilloma. From our review of published subungual acantholytic dyskeratotic acanthoma cases which include clinical images, 2 cases showed lunula notching, the same two showed macrolunula, and one had trailing lunula [5]. This suggests that these additional dermoscopic features are less common in subungual acantholytic dyskeratotic acanthoma and may help to clinically differentiate this entity from onychopapilloma.

Histologically, there are some key differences between onychopapilloma and subungual acantholytic dyskeratotic acanthoma. Onychopapilloma is a benign epithelial lesion showing papillomatosis and nail matrical epithelial metaplasia without significant cytologic atypia. In contrast, subungual acantholytic dyskeratotic acanthoma is a benign epithelial lesion showing acanthosis, acantholysis, and dykeratoses. Corps ronds may be present in some instances.

Other differential diagnoses include warty dyskeratoma, Darier disease, Hailey-Hailey disease, and squamous cell carcinoma/Bowen disease [8]. Acantholytic dyskeratosis is a histological pattern characterized by epidermal suprabasilar clefting with acantholysis and dyskeratosis of the epidermis [9]. This pattern can be found in several different conditions such as Darier disease, Hailey-Hailey disease, and warty dyskeratoma. However, conditions like Darier and Hailey-Hailey disease are associated clinically with polydactylous red bands, as opposed to subungual acantholytic dyskeratotic acanthoma and warty dyskeratoma, which are monodactylous [8].

In our case, the clinical presentation and histopathology were consistent with subungual acantholytic dyskeratotic acanthoma. Exclusive ungual Darier disease was considered unlikely as there was only one affected nail and no family history. Histologically, warty dyskeratoma was not considered due to lesion architecture, in particular the absence of cup-shaped invagination with hyperkeratosis.

In the literature, there is some debate regarding previously published cases of warty dyskeratoma. For example, Ng et al. [4] reclassify a published case of warty dyskeratoma as subungual acantholytic dyskeratotic acanthoma, citing the lack of follicular structures in the subungual region. Other experts consider warty dyskeratoma and subungual acantholytic dyskeratotic acanthoma as the same neoplasm, with warty dyskeratoma being more endophytic and displaying prominent cup-shaped invagination. We acknowledge that the terminology in this area is confusing and that the classification of a previous published case of warty dyskeratoma may be contested by some authors [4]. However, we have not sought to reclassify other published cases as we believe the interpretation of other authors to be reasonable, given the overlap between these entities.

Age at onset of subungual acantholytic dyskeratotic acanthoma appears to have 2 clusters; the first in the 10–30 years age-group and the second in the 50–60 years age-group. Pain is an inconsistent feature, and the thumb is frequently involved (all except 1 case). No published cases were associated with Darier disease.

Various etiological factors including infection and immunologic factors have been hypothesized [9]. In previously published cases, trauma is not specified as a preceding feature. In the current case, the patient works as an electrician and is ambidextrous. He recalled experiencing sustained pressure to his left thumb 2 months prior to the onset. Given the frequent involvement of the thumb in previously published cases (6 out of 7 patients) and suggestive history in our case, nail trauma could be a contributor and possibly be under-recognized. Future research could help elucidate whether trauma is a precipitant by specifically seeking a history of prior trauma and analyzing the occupation of affected patients.

As a result of the symptoms associated with the tumor and downtime after excision, our patient required time off work and recreational physical activity. In the case of subungual acantholytic dyskeratotic acanthoma, the frequent involvement of the thumb means that productivity may be affected especially for workers who require manual dexterity. Our case highlights the importance of accurate diagnosis and timely access to care for patients with nail disorders, especially when affecting the hands.

One month after excision, the patient experienced an uncomplicated recovery with good healing and persistent onycholysis of avulsed portion of nail. He was advised to self-monitor for signs of recurrence.

Written informed consent was obtained from the patient for publication of the details of their medical case and accompanying images. Ethical approval was not required for this study in accordance with local and national guidelines.

The authors have no conflicts of interest to declare.

This study was not supported by any sponsor or funder.

A.G. reviewed the literature and contributed to the principal manuscript drafting. S.L.D.M. reviewed the literature, contributed to manuscript amending, and assisted with the collection of patient data. M.D.H. assisted in the collection of patient data. S.P. interpreted the histological findings and contributed to manuscript amending. R.O. interpreted the histological findings and contributed to manuscript amending. J.S.K. had responsibility for conception of the report, patient data collection, analysis, and interpretation and contributed to manuscript drafting and critical revision of the article. All the authors issued final approval for the version to be submitted.

All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.

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