Indian Journal of Dermatology
: 2009  |  Volume : 54  |  Issue : 5  |  Page : 46--48

Subungual exostosis of the thumb - first case report in youngest age

Sanjeev Gupta1, Amit Mittal2, Sunita Gupta3, Aneet Mahendra1, Anil Kumar Dhull4,  
1 Department of Dermatology and STI, MM Institute of Medical Sciences and Research, Mullana, Ambala, India
2 Department of Radiodiagnosis, MM Institute of Medical Sciences and Research, Mullana, Ambala, India
3 Department of Medicine, MM Institute of Medical Sciences and Research, Mullana, Ambala, India
4 Department of Radiation Oncology, PG Institute of Medical Sciences and Research, Rohtak, India

Correspondence Address:
Sanjeev Gupta
H. No. B 2, Near Shiv Mandir, MM Medical College, Residential Campus, Mullana, Ambala, Haryana


Subungual exostosis (SE) is a benign osteocartilaginous tumor of the ungual apparatus, particularly of the toes. It affects both sexes equally, more frequently in the second and third decades of life. The present case highlights this entity (SE) in a six and half year old female child affecting the terminal phalanx of the right thumb. She presented to us with gradually enlarging, painless, subungual hard nodule on the right thumb. Roentogram of the hand showed bony outgrowth arising from the terminal phalanx of right thumb. Lesion was excised and sent for histopathological examination. Histology showed evidence of SE. No recurrence at postoperated site was seen till eight months of follow-up.

How to cite this article:
Gupta S, Mittal A, Gupta S, Mahendra A, Dhull AK. Subungual exostosis of the thumb - first case report in youngest age.Indian J Dermatol 2009;54:46-48

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Gupta S, Mittal A, Gupta S, Mahendra A, Dhull AK. Subungual exostosis of the thumb - first case report in youngest age. Indian J Dermatol [serial online] 2009 [cited 2020 Jan 28 ];54:46-48
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Subungual exostosis (SE) may be defined as solitary benign tumor of the bone arising on the distal phalanx beneath the nail, [1] first described by Duputyren in 1847. [2] Since then there are many case reports in the literature. It is more common in feet than in hands. In foot, the great toe is most commonly involved. Involvement of the fingers of hand by SE occurs rarely and is very rare in less than seven year of age. [3],[4],[5],[6] Advanced literature search failed to reveal a case of SE involving the thumb at a very early age of six years.

So herein, we report the very first case of SE involving the thumb in a six and half year old-female child.

 Case History

A six and half year old-female child presented with the complaint of a slowly growing, slightly tender nodular growth under the right thumb nail for last seven to eight months. Prior to that, her thumb nail was normal in appearance. The patient herself and her mother did not recall any major or minor trauma affecting this nail. There was no history of chronic infection of the right terminal phalanx of the thumb. The patient complained of mild pain in the distal part of the nail while writing.

The subungual nodular growth was measuring around 11cm. It was well-defined in outline, bony hard in consistency, slightly tender and with a hyperkeratotic surface [Figure 1]. Overlying nail plate was markedly elevated and appeared normal. A presumptive diagnosis of subungual wart was made but repeated attempts at superficial paring of the topmost layer of the hyperkeratotic subungual area did not cause any improvement in the lesion. Because of the bony hard consistency of the lesion patient was sent for the radiological examination. Radiographs of the hand [Figure 2], taken in antero-posterior and oblique projections revealed an outgrowth of trabeculated bone projecting from the distal phalanx of the right thumb on the dorsal aspect, with intact well-defined cortical margins. There was no evidence of calcification of soft tissues. No destructive changes were noted in the distal phalanx to suggest the possibility of a malignant lesion. These radiological findings were consistent with the diagnosis of subungual exostosis. The patient underwent excision of the exostosis with satisfactory relief of symptoms. Histopathologic analysis of the lesion showed a base of lamellated trabecular bone covered by a thin hyaline fibrocartilage cap consistent with the diagnosis of subungual exostosis. There has been no local recurrence till eight months after the patient underwent excision of the growth.


Subungual exostosis is an uncommon benign bone tumor arising in the distal phalanx of a digit, beneath or adjacent to the nail bed. It is considered to be a rare variant of osteochondroma. [7] Almost invariably, it is a solitary lesion, mostly asymptomatic but sometimes pain, ulceration of the nail bed or surrounding tissue secondary infection may occur. [8] This usually solitary lesion, most often, occurs on the large toe but also has occurred on the lesser toes and even on fingers. [4] Subungual exostosis usually develop during adolescence and are more common in females than males. [9],[10],[11] Subungual exostosis is very rare under seven years of age. [4],[12]

A solitary exostosis occurring on the finger is a rarely reported entity. Recently, Guarneri et al , [4] have reported SE of great toe in six years old female child. We for the first time are reporting subungual exostosis affecting the thumb in a six and a half years old-female patient.

The cause of subungual exostosis is unknown. Many factors have been suggested for this exostosis including trauma, chronic infection, tumor, a hereditary abnormality or activation of a cartilaginous rest. [1] Subungual exostosis may represent cartilaginous metaplasia occurring in response to acute or chronic irritation and often, trauma is the precipitating factor. [3] The recent identification of a recurrent chromosomal translocation t(X;6)(q24-q26;q15-21) in short-term-cultured tumor cells strongly suggests that subungual exostosis is a neoplastic lesion caused by rearrangement of genes in the two breakpoints. [13] Clinically, the differential diagnosis may include the following: subungual verruca, granuloma pyogenicum, glomus tumor, carcinoma of the nail bed, melanotic whitlow, keratoacanthoma, subungual epidermoid inclusions, enchondroma, konen tumor and ingrowing toe nail. [3],[7],[14]

Diagnosis of the SE most of the time is made on plain radiographs. On plain radiographs, SE appears as trabecular bony outgrowth arising from the parent bone of terminal phalanx of the toe or finger. The cortex and medulla of outgrowth are continuous with the parent bone. The outgrowth has well defined cortical margins without any destruction of the parent bone. [8] The cartilaginous cap is not visualized as it is radiolucent and can be seen on histopathology.

At the histopathological examination, subungual exostosis resembles an osseous callus in its morphologic gradations to mature bony trabeculae: a base of normal-appearing trabecular bone is covered by a fibro cartilage cap with enchondral ossification proceeding from base to cap. [15],[16]

The treatment of subungual exostosis remains surgical. Performed under a digital block, complete removal of the tumor with subsequent curettage of the base is necessary to avoid recurrences. [17],[18]

The idea of reporting this case is to highlight the rare occurrence of subungual exostosis on thumb and that too at an early age of six and a half years and to stress that while examining subungual lesions, the possibility of subungual exostosis should be considered as it is often missed because X-ray films are routinely not advised for such type of lesions.


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