Unusual localization and presentation of osteoid osteoma mimicking juvenile spondyloarthritis: a case report
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Osteoid osteoma is a painful benign skeletal tumour of unknown aetiology. Most often it occurs in the long bones of extremities and responds well to nonsteroidal anti-inflammatory medications. However, unusual localization and atypical presentation of this tumour might present a diagnostic challenge, especially if symptoms mimic that indicative of juvenile spondyloarthritis.
A misdiagnosed ten-and-a-half-year-old girl with osteoid osteoma involving the distal phalanx of a little finger is presented. Her initial symptoms were pain and swelling of the little finger resembling dactylitis, while various imaging modalities showed signs of tenosynovitis, indicating a possible development of juvenile spondyloarthritis. Several trials of different non-steroid anti-inflammatory drugs gave no satisfactory results and ultrasound guided triamcinolone-hexacetonide injection provided only a short relief. Finally, almost three years after initial presentation, persistent clinical symptoms warranted repeated imaging that raised suspicion of an osteoid osteoma. Directed treatment with surgical intervention led to almost immediate and complete resolution of her symptoms.
Osteoid osteoma should be suspected in case of a tender swelling of a digit in children and adolescents, regardless of initial imaging findings and clinical presentation. Early diagnosis and treatment of this benign condition can have a substantial impact on quality of life of patients and their families and protect them from many unnecessary diagnostic procedures and treatment.
KeywordsDactylitis Sausage digit Juvenile spondyloarthritis Distal phalanx osteoid osteoma
C reactive protein
Distal interphalangeal joint
Estimated sedimentation rate
Magnetic resonance imaging
Nonsteroidal anti-inflammatory drugs
- Technetium 99 m-MDP
Technetium 99 m-methyl diphosphonate
Osteoid osteoma (OO) is the third most common benign bone tumour typically found in children, adolescents, and young adults between 10 and 35 years of age [1, 2]. It accounts for approximately 3% of all primary bone tumours, and has a strong male predilection (male to female ratio 3:1) . Histologically it is characterized by a network of dilated vessels, osteoblasts, osteoid, and woven bone which comprises a central nidus surrounded by a rim of reactive osteosclerosis . Radiographically, a lytic lucent area less than 1.5 cm in diameter is most commonly demonstrated, making it hard to notice, especially in the early stage of the disease [1, 4]. The most common localization of such lesions are the long bones of lower limbs, while OO in the distal finger phalanx has been rarely reported [5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22]. The typical clinical presentation of OO includes progressively increasing pain that is worse at night and responsive to non-steroid anti-inflammatory drugs (NSAIDs). Nevertheless, substantial variations have been described, causing a delay in diagnosis, inadequate treatment, and persistence of symptoms, particularly when regions other than the lower limbs are involved [17, 23]. With fingers affected, the clinical features might mimic dactylitis, sausage-like tender swelling of one or more digits extending beyond the joint margin . Commonly, dactylitis is associated with juvenile spondyloarthritis, group of chronic rheumatic diseases seen in paediatric population more often than any of the bone tumours .
The aim of our report is to address the diagnostic pitfalls observed in atypical OO and emphasize OO as a possible cause of long-lasting symptoms resembling those seen in juvenile spondyloarthritis.
Discussion and conclusions
The presented case of OO at an unusual localization with an atypical presentation took almost three years to be correctly diagnosed and treated (Additional file 1). In the majority of cases, OO is much easier to diagnose based on localization and clinical presentation. However, without typical signs and symptoms it may present a great burden to both the patient and family as well as the physicians involved. Clinically, a painful fingertip swelling may represent a heterogenous group of differential diagnoses including but not limited to trauma, whitlow or paronychia, osteomyelitis, glomus tumour, subungual exostosis, arthritis, soft tissue rheumatism (e.g. tenosynovitis), and OO [11, 15, 26]. Therefore, the average delay of more than two years between the onset of symptoms and the first special investigations have been reported in cases of OO in the distal finger phalanx .
While uncommon, other cases of OO of the distal phalanx have been presented in children around 10 years of age. However, all cases share similar clinical presentations with nail hypertrophy, local enlargement and night pain as the main symptoms [6, 7, 8, 9, 10]. In our case, OO caused pain and swelling of distal finger phalanx that extended beyond the borders of the osseous structures, giving an appearance of a “sausage digit”, commonly referred as dactylitis. This finding is not very common in children, and when tuberculosis, infection or sickle cell crisis are excluded in majority of cases dactylitis is associated with juvenile spondyloarthritis [27, 28, 29].
In our patient, three imaging modalities (MSUS, MRI, skeletal scintigraphy) demonstrated characteristic signs indicative of juvenile spondyloarthritis, although no other joint and/or enthesis was involved, and despite no family history of HLA-B27-associated diseases. Therefore, after several years of follow up with persistent symptoms, and without adequate response to NSAIDs or intraarticular glucocorticoids, re-evaluation by a second paediatric orthopaedics was suspicious for another pathology. Finally, three years after the initial symptoms and various, mostly inadequate treatment trials, repeated imaging led to the diagnosis of OO of the distal phalanx as a possible cause of the disturbances.
Although OO and rheumatic diseases have almost completely different underlying mechanisms, they do both share excessive production of prostaglandins at the affected site and therefore benefit from NSAIDs treatment. Nevertheless, several reports demonstrated that conservative management with NSAIDs may take years before the OO is resolved [30, 31, 32]. Therefore, it is not surprising our patient did not achieve sustained remission with this treatment modality.
The other dilemma elicited in our case is the sensitivity and specificity of various imaging modalities in the assessment of OO. While in the vast majority of cases OO can be easily identified with plain radiographs, computed tomography (CT) scans, MRI and/or skeletal scintigraphy, there are some areas of the skeleton, including spine, femoral neck and small bones of hands and feet, that are difficult to assess [33, 34]. Although dynamic contrast-enhanced MRI has been suggested as being useful to detect and to differentiate this tumour from OO-mimicking lesions, longstanding literature still supports thin-section CT as the most specific imaging study [17, 35, 36]. Besides the unexpected localization, the small size of the tumour (typically less-than 1.5–2 cm) could also be a cause of misdiagnosis . Finally, recent literature also gives an argument in favour of the diagnostic riddle concerning atypical OO, with major issues being prolonged impairment and overtreatment .
In conclusion, we would like to emphasize OO as a possible cause of a tender swelling of a digit, a symptom more commonly seen in juvenile spondyloarthritis. Although OO is a benign disease, it might represent a diagnostic and treatment challenge for paediatric rheumatologists, indicating the need for consultation with other specialists, including the paediatric orthopaedics.
Authors would like thank to Assistant Professor Martin J. Morrison, III, MD; (Educational Consultant for DePuy Synthes Spine and Educational Consultant for OrthoPediatrics); Loma Linda University Department of Orthopaedic Surgery Loma Linda, CA 92354 USA for text editing assistance.
The authors state that this work has not received financial support.
Availability of data and materials
The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.
JV, LL, SS, participated in the conception and design of the study. They contributed to analysis and interpretation of the data and drafting of the manuscript. They approved the final version of the manuscript to be submitted, and agreed to be accountable for all aspects of the work.
MH and DB treated the patient and participated in the conception and design of the study. They critically revised the manuscript for important intellectual content. They approved the final version of the manuscript to be submitted, and agreed to be accountable for all aspects of the work.
Ethics approval and consent to participate
The local Institutional review board (IRB) at the Children’s Hospital Zagreb was consulted prior to undertaking this case report. Written informed consent was obtained from patient’s parent and patient presented in the case report.
Consent for publication
This manuscript has the consent of the patient and patient’s parent for the use of her data and image of fingers. The authors obtained the written consent of the patient and patient’s parent for the publication of the data and images that appear in the article.
The authors declare that they have no competing interests.
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