Hidden in plain sight: the diagnostic dilemma of tuberculous synovitis: a case report

Abstract

Tuberculous synovitis (TS) is an infrequent yet significant manifestation of tuberculosis (TB), particularly in regions where TB is endemic. The clinical presentation of TS is often nonspecific yet distinctive, and diagnosis is confirmed by histopathological examination. Anti-TB therapy is the cornerstone of treatment, although the necessity of surgical intervention remains debated. A case was reported of a 73-year-old female patient who complained of left wrist pain and swelling for the past 3 years. The left wrist was swollen from the metacarpophalangeal joints to the mid-forearm. Radiography on the left forearm revealed extensive, mixed predominant osteolytic and sclerotic bony lesions affecting all the carpal bones. These findings were associated with increased size of a hyperdense soft tissue swelling. Magnetic resonance imaging revealed rim-enhancing multiple encapsulated cystic fluid collections at the distal radioulnar and carpal regions. A biopsy of the left wrist was performed, revealing TS. The patient was subsequently started with anti-TB therapy.

Introduction

Tuberculous synovitis (TS) is a chronic granulomatous inflammation of the synovium caused by Mycobacterium tuberculosis. It results from either hematogenous spread or direct extension from adjacent osteoarticular tuberculosis (TB). The infection induces a delayed hypersensitivity reaction, forming caseating granulomas within the synovium. Progressive synovial thickening and joint effusion can lead to cartilage destruction and joint deformity [1]. TS often presents as monoarticular joint swelling, pain, and restricted movement. It is frequently misdiagnosed as inflammatory arthritis, which can delay appropriate treatment.

TS most commonly affects large weight-bearing joints, although smaller joints may be involved. The knee joint is the most frequently affected site, owing to its extensive synovial surface and rich vascular supply. Following the knee, the hip joint is another common site, particularly in children and young adults, often presenting with pain, restricted mobility, and progressive joint destruction when left untreated.

The ankle is the third most involved joint and typically presents with persistent swelling and stiffness. The wrist, which is less frequently affected, is the most involved small joint. Its involvement is significant due to its functional importance and the potential for misdiagnosis as other inflammatory arthritides, such as rheumatoid arthritis [2]. If not treated early, TB of the wrist can lead to severe joint destruction and loss of function. In all cases, the infection is monoarticular and progresses insidiously, often resulting in delayed diagnosis. This report describes a rare case of TS affecting the wrist, which presented with progressive swelling and impaired function, a clinical pattern infrequently documented in the current literature.

Case Report

A 73-year-old female patient, previously healthy, presented to the orthopedic clinic with left forearm pain and swelling that had persisted for 3 years. Her symptoms started after a fall during which extended her left hand to break the impact while on a picnic. After the fall, the patient developed pain and swelling in the left wrist and forearm. Although an initial radiograph at a private clinic showed no abnormalities, her symptoms persisted. The patient underwent multiple wrist injections as part of ongoing treatment; however, the pain persisted. In August 2023, after approximately 3 years of ongoing symptoms, the patient sought treatment at the hospital. The pain and swelling in the left forearm worsened, severely impairing hand function, particularly in gripping and grasping. The patient denied experiencing any constitutional symptoms.

On examination, diffuse, firm swelling was observed around the left wrist, without any associated skin changes. The wrist exhibited a reduced range of motion and noticeable wasting of the thenar and hypothenar muscles. Neurological examination revealed an inability to perform the “OK” sign. Finger strength was graded at 2/7, with reduced sensation on the ulnar side and marked hypothenar muscles wasting. Blood parameters were mostly within normal limits, except for C-reactive protein level of 9.2 mg/L and an erythrocyte sedimentation rate (ESR) of 37 mm/h.

A left forearm radiograph displayed extensive mixed osteolytic and sclerotic bony lesions involving all carpal bones and the bases of the metacarpal bones, with narrowing of the intercarpal and radiocarpal joints (Figure 1). A hyperdense soft tissue swelling was additionally noted, with evidence of interval size progression. Ultrasound examination revealed a multiloculated, heterogeneous collection at the distal forearm, extending into the wrist joint and proximal carpal bones (Figure 2).

Figure. 1.

Left forearm radiograph: anteroposterior view (A) and lateral view (B). Soft tissue swelling with extensive mixed predominant osteolytic and sclerotic bony lesions.

Figure. 2.

Ultrasound of the left hand: multiloculated, heterogeneous collection at the distal forearm, extending into the wrist joint and proximal carpal bones. (A) Volar aspect distal forearm transverse view. (B) Longitudinal view.

Contrast-enhanced magnetic resonance imaging (MRI) of the distal radioulnar and carpal regions demonstrated multiple rim-enhancing encapsulated cystic fluid collections (Figure 3). The differential diagnoses included abscesses, bursitis, avascular necrosis, and osteomyelitic changes affecting the carpal bones, distal radius and ulna articular surfaces, and the bases of second to fourth metacarpal bones. A QuantiFERON-TB Gold In-Tube test, conducted in December 2023, returned a positive result, indicating a probable M. tuberculosis infection. The patient was subsequently started on anti-TB therapy and referred to an occupational therapist for functional rehabilitation.

Figure. 3.

Magnetic resonance imaging of the left forearm with contrast: rim-enhancing, multiple encapsulated cystic fluid collections at the distal radioulnar and carpal regions.

Written informed consent was obtained from the patient for publication of this case report.

Discussion

TS, particularly when affecting the wrist, is a rare condition that presents significant diagnostic challenges. In this case, the patient’s symptoms, gradual swelling and localized pain in the wrist that progressed to articular damage with abscess discharges [3], were consistent with the indolent nature of the disease, despite the absence of systemic signs such as fever or wight loss. This slow progression and the absence of systemic symptoms often result in a delayed diagnosis, as such presentations can be mistakenly attributed to more common conditions, such as inflammatory arthritis. Although trauma does not directly cause TS, some studies have indicated that minor injuries may disrupt local immune defenses or blood flow, possibly triggering the activation of a previously dormant infection [4].

The diagnosis in our case was supported by imaging findings, which played a crucial role in confirming the suspicion of tuberculous involvement. Although inflammatory markers such as ESR were elevated, they were nonspecific, highlighting the need for further imaging. Ultrasound is instrumental in detecting the synovial sheath volume, which encases the tendon, along with identifying tendon thickening or fluid accumulation [5], whereas MRI provides a clearer picture of synovial alterations, including tendon sheath involvement and early signs of bone erosion. These findings are consistent with existing literature, which underscores the effectiveness of MRI in diagnosing musculoskeletal TB owing to its ability to detect soft tissue changes and bone involvement at early stages.

Although TB of the wrist is uncommon, it should be included in the differential diagnosis of persistent joint swelling, particularly in patients with risk factors such as a history of TB or immunocompromised status. In this case, the diagnosis was made in a timely manner, and the patient promptly initiated appropriate anti-TB therapy. The treatment approach, which includes both pharmacological management with anti-TB medications and wrist splinting for joint stability, is consistent with current recommendations for managing musculoskeletal TB.

Surgical intervention is typically reserved for cases with significant bone or cartilage damage or when patients do not respond to drug therapy [6]. Fortunately, in this case, surgery was not required, as the patient responded well to medication. However, as the literature suggests, early surgical intervention may be necessary in cases of large abscess formation, extensive joint destruction, or poor response to initial therapy.

This case highlights the importance of considering TS in the differential diagnosis of chronic monoarticular joint disease, particularly when typical symptoms persist despite standard treatment. Timely recognition and intervention are crucial for preventing long-term joint dysfunction and improving patient outcomes.

In conclusion, TS is an uncommon condition that poses diagnostic challenges owing to its ambiguous clinical manifestations. Laboratory analyses, imaging techniques (MRI, ultrasound, and plain radiography), and microbiological test assist in diagnosis; nonetheless, histopathology remains the gold standard. The primary treatment is conservative and includes anti-TB medications; however, surgical intervention may be necessary in complex or advanced cases.