A 15 year old boy presented with generalised swelling of right little toe with no prior history of injury.
A 15 year old boy presented with a 3-month history of an enlarging, minimally painful swelling of the tip of right little toe. The swelling was generalised with no clear cut demarcations from the underlying bone and was firm in consistency with minimal tenderness on palpation. The overlying nail was thickened and spoon-shaped. No similar swellings were found elsewhere. Radiography showed bony erosion of the distal phalynx of little toe (figure 1). MRI showed a lesion enveloping the terminal phalanx of the little toe from below and laterally, with further extension of it between the dorsal surface of the bone and the nail. The lesion was low signal on the T1 sequence (figure 2a), high signal on the fat suppressed sequence (figs 2b - d) and there was no enhancement within it following gadolinium administration. No signal void to suggest calcification within the mass was demonstrated. The scan confirmed pressure erosion of the tuft of the distal phalanx. Surgical excision of the lesion was performed and histopathological assessment of the specimen showed it to be consistent with a subungual exostosis with predominant chondroid metaplasia.
Subungual exostosis is a rare osteo-cartilaginous benign tumour arising usually from the distal phalynx of the toes, more commonly from the hallux. Very rarely they can be found in the hands. The term ‘exostosis’ is a misnomer as there is no continuity with the underlying bone. Females are affected twice as males and the lesions occur mostly during the second decade. The precise cause is not clear, but factors like trauma, chronic infection and local irritation are often implicated. The underlying pathology is the initial growth of fibro-cartilaginous tissue, which later ossifies to a varying degree. It differs from osteochondroma, which is a congenital lesion arising from the metaphysis of the underlying bone. Clinically patients may present with swelling in the distal phalynx, with some degree of tenderness often after an episode of trauma. The position of the lesion is almost always dorso-medial. Possible differential diagnoses for the lesion include osteochondroma, glomus tumour, squamous cell carcinoma and melanoma. Radiologically, the appearances can vary according to the amount of calcification. Generally the outgrowth has features of cancellous bone without a defined cortex. During the pre-ossifying stage the underlying bone can be eroded due to the compression by the tumour. Surgical excision and curettage of the base is the treatment of choice. Rarely recurrences can occur if the base is not excised completely.
Subungual exostosis of the liitle toe
Based on the provided imaging of the right little toe (including X-ray and MRI), the following findings are noted:
Considering the patient’s age, clinical presentations (mild pain, no apparent history of trauma), and imaging findings, the following conditions or differential diagnoses can be considered:
Taking into account the patient’s clinical presentation (a 15-year-old male with no significant history of trauma, mild local pain with swelling), imaging findings (dorsal proliferation of the distal phalanx, not continuous with the bone shaft, showing fibrous-cartilaginous changes), and pathophysiological characteristics, the most likely diagnosis is:
Subungual exostosis.
If there is still any doubt or further clarification is needed, surgical excision of the lesion followed by pathological examination can confirm the diagnosis and assess the nature of any tumor cells.
The most effective treatment for this condition is typically surgical excision, along with curettage of the base to reduce the risk of recurrence. The following are the recommended treatment and rehabilitation guidelines:
To promote functional recovery of the affected toe and reduce pain and swelling, a gradual, individualized rehabilitation program should be established. The FITT-VP principle can be referenced:
Throughout rehabilitation, pay attention to any signs of recurrent swelling or pain in the affected toe. If significant discomfort emerges, seek timely medical consultation.
Precautions: If the patient has poor bone quality or a high sensitivity to pain, the exercise regimen should be slowed down accordingly. In cases of persistent infection or signs of poor wound healing, seek medical attention promptly for appropriate medication or other interventions.
This report provides a reference analysis based on the existing medical history and imaging data, and does not replace in-person consultation or the diagnostic and treatment plans provided by a professional medical institution. If you have any questions or if symptoms worsen, please seek professional medical attention promptly.
Subungual exostosis of the liitle toe
