Onychopapilloma: A Report of Three Cases Presenting with Various Longitudinal Chromonychia

Dear Editor:

Onychopapilloma is an uncommon benign tumor of the distal matrix and nail bed characterized by localized distal subungual keratosis¹. Several cases have been reported since the term 'onychopapilloma' was proposed by Baran and Perrin in 2000¹,²,³,⁴,⁵. Herein, we report three cases of onychopapilloma presenting with various longitudinal chromonychia.

Two men and one woman with a median age of 47.8 years (range, 35~67 years) developed onychopapilloma. The average disease duration was 15.5 months and showed great variation (range, 0.8~48.0 months). The affected nails showed various chromonychia, including longitudinal erythronychia, longitudinal reddish-yellow longitudinal chromonychia and multiple yellowish chromonychia (Fig. 1A~C). All three patients reported pain, tenderness, and cosmetic problems. Mycological evaluation, including a KOH smear, fungal culture, and histopathologic examination, revealed negative results. Histopathologically, a digitation of the epithelium parallel to the affected nail plate was present with abundant eosinophilic cytoplasm and irregular thickening (Fig. 1, A3~C3). All three patients were treated with nail extraction and curettage of the hyperkeratotic lesion. After post-treatment follow-up period (mean, 6.7 months), two patients showed good responses without nail deformities or recurrence, and one patient showed a partial response with persistent mild subungual hyperkeratosis (Fig. 1, A2~C2). Most cases of onychopapilloma present as a localized longitudinal ridge of the nail bed that is expanded at the distal aspect as a subungual keratosis with longitudinal erythronychia². However, onychopapilloma can also present with longitudinal melanonychia and leukonychia³,⁴. The patients described herein showed various degrees of chromonychia including red, reddish-yellow, and yellow. Therefore, the color of the longitudinal ridge is not consistent among patients. We also suggest that a longitudinal ridge or chromonychia that extends to the proximal area is an important clinical feature of onychopapilloma. Although the pathogenesis of onychopapilloma is not fully understood, three hypotheses could be suggested: i) neoplastic hyperplasia of the nail bed epithelium, ii) reactive hyperplasia of the nail bed epithelium due to chronic irritation or trauma, and iii) a concomitant response with other inflammatory nail diseases such as lichen planus⁵. All of our patients complained of pain, especially tenderness when pressing the nail plate, which may have been due to the hyperkeratotic mass compressing the nail bed.

Fig. 1. Clinical appearances of three cases of onychopapilloma. (A) Longitudinal reddish-yellow colored chromonychia was seen on the left thumbnail (patient 1). (A2) Post-treatment clinical view (after one month). (B) Multiple longitudinal yellowish chromonychia with marked subungual hyperkeratosis was seen on the right thumbnail (patient 2). (B2) Post-treatment clinical view (after 7 months). (C) Multiple longitudinal red streaks were seen on the left thumbnail. (C2) Post-treatment clinical view (after 12 months). (A1~C1) The nail plate was extracted and 2 mm punch biopsy and curettage were performed on the nail bed (arrows). (A3~C3) There was acanthosis of the epithelium of the nail bed (A3, B3), a digitation of the epithelium parallel to the nail plate (A3) and a thickened epithelium (C3) (H&E, ×100).

We performed nail extraction and curettage of all the hyperkeratotic lesions on the nail bed. Based on our experience, surgical treatment to remove the hyperkeratotic tumor mass by curettage can be one of the acceptable methods for improving the patient's symptoms. Additionally, the removed tissue must undergo histopathological examination to differentiate it from other benign tumors such as keratoacanthomas, inflammatory conditions such as fungal infections, and malignant conditions such as Bowen's disease or squamous cell carcinoma¹.

In conclusion, we reported three cases of onychopapilloma presenting with diverse clinical features including chromonychia of various colors, onycholysis, and hemorrhagic spots. To our knowledge, onychopapilloma has never been reported in the Korean dermatological literature. We hope that when patients present with longitudinal chromonychia with tenderness, dermatologists should be aware of the possibility of onychopapilloma.