Hip Pain in a Kidney Transplant Recipient

A 45-year-old kidney transplant recipient (KTR) presented with right hip pain and restriction of joint movements for a 1-week duration in his 3^rd month after transplantation. Examination revealed an antalgic gait and diffuse tenderness in the right hip joint line. Contrast Magnetic Resonance imaging (MRI) showed moderate right hip joint effusion with smoothly enhancing synovial thickening suggestive of right hip synovitis [Figure 1]. He underwent an ultrasound-guided aspiration of the right hip joint, and synovial fluid showed a white blood cell count of 13,147 cells/μL with 70% polymorphs. Biochemical analysis showed a protein of 5.7 g/dL, lactate dehydrogenase (LDH) of 2148 IU/L, and adenosine deaminase (ADA) of 42.4 IU/L. Synovial fluid microbiology was unrevealing. He underwent an open arthrotomy, joint debridement, and synovial biopsy. It showed fibrocollagenous tissue with well-formed epithelioid granuloma and chronic inflammatory infiltrates with focal areas of necrosis [Figure 2a-b]. The Ziehl-Neelsen stain for acid-fast bacilli was negative in the biopsy [Figure 2c]. GeneXpert for Mycobacterium tuberculosis was positive in synovial tissue. His pain and joint movements improved after anti-tuberculous treatment (ATT).

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Figure 1:

(a) Post contrast T1 weighted MRI coronal sequence of the right hip shows extensive synovial thickening and enhancement (yellow arrow). Erosions (white arrows) involving the acetabulum and the fovea of the femoral head are also seen. (b) Axial proton density (fat-saturated) sequence of the bilateral hips shows subarticular oedema (white arrows) involving the anterior pillar of the right acetabulum and the right femoral head around the fovea.

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Figure 2:

(a) Section shows synovial tissue with a large area of caseous necrosis (white star) surrounded by granulomatous response, occasional Langhans’ giant cells (white arrow) and lymphocytic infiltration. H&E stain, x 100. (b) Section shows higher magnification of the focus of caseation (white star) surrounded by aggregates of epithelioid histiocytes (black oval shape) forming a granuloma. H&E stain, x 400. (c) Section shows negative acid-fast staining in the focus of the granulomatous response. Ziehl Neelsen stain, x400. H&E: Hematoxylin and Eosin.

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The immunosuppression-induced reactivation of the latent mycobacterial infection mainly causes tuberculosis (TB) after solid organ transplantation (SOT).¹ TB involvement of the bone and joints is seen in up to 10% of extra-pulmonary cases.² The spine, hip, and knee joints are the commonly affected sites. Pathogenesis involves the hematogenous spread of TB bacilli to the bone or synovial tissue from the site of primary infection.³

The MRI findings include synovial effusion, sub-articular edema, bone erosions, and synovial thickening. The synovial fluid analysis shows a predominantly neutrophilic leucocytosis, but can also be lymphocytic in up to 20% of cases.⁴ A definitive diagnosis requires a synovial tissue biopsy for histopathology and culture. The minimum duration of treatment for tuberculosis in SOT recipients is 9 months.⁵