What is your diagnosis?

Figure 1 Firm nodular lesion on the distal surface of the third finger of the right foot, compatible with subungual exostosis.  

Figure 2 Exostotic proliferation in the phalanx of the third finger of the right foot (arrow). 

Discussion

The patient was diagnosed with SE and referred to orthopedic consultation. Excision of the nodule was performed without intercurrences. Anatomopathology confirmed the diagnosis of SE.

SE is a painful benign osteochondral proliferation of the distal phalanx of the fingers or toes, most commonly affecting the hallux.^1-5 Progressive growth of the lesion may cause nail lifting and deformity.⁴ The etiology of SE is unknown, although trauma and chronic infection seem to play a role.^3,5 Half of the cases occur in patients under the age of 18 years, and females are predominantly affected.^2,5 The differential diagnosis is broad and should include other subungual masses such as osteochondroma, pyogenic granuloma, keratoacanthoma, wart, or fibroma.⁴ Radiograph of the affected digit is essential for diagnosis and shows a dorsal or dorsomedial surface proliferation of the distal phalanx.^1,5 Histopathology typically shows endochondral ossification with lamellar trabeculae covered by a fibrocartilaginous cap.^1,4 As this is usually a progressive condition, treatment consists of complete marginal surgical excision.^1-5 Postoperative nail deformity may persist, and recurrence has been reported.^1,2

Although SE is not a rare entity, a diagnostic delay of 12 months is common,² highlighting the importance of a high index of suspicion for this entity by all physicians working with children, as it can affect their quality of life.³

Authorship

Susana C Teixeira - Conceptualization; Writing - original draft; Writing - review & editing

Pedro Marinho - Writing - review & editing

Miguel Oliveira - Writing - review & editing

Susana Machado - Patient´s assistant physician; Validation; Writing - review & editing