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Received：November 19, 2015, Revised：December 23, 2015, Accepted：December 24, 2015

Corresponding to：Hee Jin Park, Department of Rheumatology, Catholic Kwandong University International St. Mary’s Hospital, 25 Simgok-ro 100beon-gil, Seo-gu, Incheon 22711, Korea. E-mail：yolliko@ish.ac.kr

pISSN: 2093-940X, eISSN: 2233-4718Copyright ⓒ 2016 by The Korean College of Rheumatology. All rights reserved.This is a Free Access article, which permits unrestricted non-commerical use, distribution, and reproduction in any medium, provided the original work is properly cited.

Case ReportJournal of Rheumatic Diseases Vol. 23, No. 5, October, 2016https://doi.org/10.4078/jrd.2016.23.5.316

A Case of Idiopathic Massive Rice Bodies in the Knee Joint without Rheumatoid Arthritis or Tuberculosis and a Literature Review

Whan Yong Chung1, Ji-Sun Song2, Hwa Eun Oh3, Hee Jin Park4

Departments of 1Orthopedics, 2Pathology, and 4Rheumatology, Catholic Kwandong University International St. Mary’s Hospital, Incheon, 3Department of Pathology, Korea University Ansan Hospital, Ansan, Korea

Rice bodies are materials with an amorphous nucleus and a fibrin layer found floating in the synovial space and bursa. These bodies have often been detected in patients with rheumatoid arthritis, tuberculous arthritis, and bursitis. Although the etiology and pathogenesis of rice bodies are not yet fully understood, it has been hypothesized that they might be caused by chronic in-flammation originating from the synovium. However, we report on a case of idiopathic massive rice bodies in the knee joint without evidence of inflammatory articular disease or infection including rheumatoid arthritis, seronegative spondyloarthri-tides, tuberculosis, or bacterial or fungal infection. (J Rheum Dis 2016;23:316-320)

Key Words. Rice body, Knee, Rheumatoid arthritis, Tuberculosis

INTRODUCTION

Floating rice-like particles in the synovial space could be found in the inflammatory joint diseases. These particles are known as rice bodies and were first reported by Reise in 1895 in tuberculous arthritis [1]. Rice bodies have been found in the synovial space in patients with rheuma-toid arthritis or seronegative spondyloarthritis [2] and in the bursa [3] and around tendon sheaths [4] in associa-tion with inflammation. However, we experienced a case with massive rice bodies in the knee joint without any in-flammatory or infective evidence and report these idio-pathic rice bodies with an associated literature review.

CASE REPORT

A 46-year-old male had developed discomfort in the right knee one year ago, and aggravated swelling and pain two month ago. For these symptoms, he visited to the out-patient clinic of orthopedics department. He did not have

any medical history and previous joint problems. He worked in an office and had not experienced any traumatic events involving the right knee joint. He felt discomfort when climbing stairs but no definite tenderness and warmth in the right knee. He did not have any symptoms in the other joints and had not experienced inflammatory back pain, uveitis, psoriasis, or inflammatory bowel disease. At admission, his white blood cell count was 3,870/μL, hemoglobin was 14.9 g/dL, and platelet count was 224,000/μL. Erythrocyte sediment rate was 6 mm/hr, and C-reactive protein was 3.18 mg/L (normal range, 0∼5 mg/L). Antinuclear antibody, rheumatoid fac-tor, anti-cyclic citrullinated protein antibody, and human histocompatibility leukocyte antigen (HLA) B27 were all negative. Magnetic resonance imaging (MRI) of the knee showed a large amount of joint effusion with numerous low-signal foci in the suprapatellar bursa against a back-ground of fluid signal intensity on T2-weighted image and intact anterior and posterior cruciate ligaments and collat-eral ligaments, as shown in Figure 1. Arthroscopic syno-

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Figure 2. Gross morphology of rice bodies in the washing synovial fluid and arthroscopic findings. (A) Many white amorphous ma-terials were found in the washing synovial fluid collected through arthroscopic irrigation. Arthroscopic findings were consistent with rice bodies in the suprapatellar space (B) and revealed a normal synovium (C).

Figure 1. Magnetic resonance images of the right knee. (A) T1-weighted image (T1WI) and (B∼D) T2-weighted images (T2WI) showed a large amount of joint effusion with numerous low-signal foci against a back-ground of fluid signal intensity on T2WI. Anterior and posteri-or cruciate ligaments and collat-eral ligaments were intact.

vectomy of the right knee joint was conducted for diag-nosis and revealed numerous rice bodies in the synovial space, but no definite synovial proliferation, as shown in Figure 2. Microscopic pathology of these materials re-vealed multiple nodular fibrocartilaginous tissues con-sistent with rice bodies and clean synovium without any synovial hyperplasia and inflammatory cells as shown in Figure 3. The results of bacterial, fungal, and acid-fast ba-

cilli (AFB) culture studies from the synovium and washing synovial fluid were all negative, and real-time polymerase chain reaction (PCR) for non-tuberculous mycobacterium (NTM) of synovium was also negative. His symptoms im-proved after synovectomy without any medications and continue to be stable 6 months later.

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Figure 3. Pathology of rice body and synovium. (A) Microscopic examination (H&E, x40) revealed multiple nodular fi-brocartilaginous tissues consistent with rice bodies. (B) The synovium of the knee joint (H&E, x100) showed a histologically cleansynovial surface.

Table 1. Clinical characteristics and prognosis after treatment of idiopathic rice bodies

Age (yr)/

gender

Site ofrice body

Duration of symptom

Laboratory data

Culture Pathology TreatmentFollow-up duration

Prog-nosis

Refe-rence

38/F Right ankle 2 yr RF/ANA negative

PPD skin test (−)

Tenosynovitis Tenosynovectomy 5 yr No recurr

4

51/M Left wrist 2 yr RF/ANA/HLA B27 negative

Tenosynovitis Radicalsynovectomy

1 yr No recurr

11

31/M Left knee 3 mo ESR/CRP normal

Bacterial culture (−)

Synovitis Synovectomy 2 yr No recurr

12

RF/ANA negative

AFB (−)

4/F Both shoulder and knee

Unknown ESR (18 mm/hr)/CRP normalRF/ANA negative

Surgery without synovectomy

1 yr No recurr

13

11/M Left knee 4 mo ESR/CRP normal

Chronic synovitis

Subtotal synovectomy

2.5 yr No recurr

14

RF negative54/F Both shoulder 14 mo ESR/CRP

normalInflammatory

bursitisSynovectomy 3 mo No

recurr 9

RF/ANA negative

F: female, M: male, ANA: anti-nuclear antibodies, AFB: acid-fast bacilli, CRP: C-reactive protein, ESR: erythrocyte sedimentation rate, HLA: human histocompatibility leukocyte antigen, PPD: purified protein derivative, RF: rheumatoid factor, recurr: recurrence.

DISCUSSION

Rice bodies were most commonly detected in rheuma-toid arthritis [2], tuberculous arthritis, and bursitis [5,6]. Rice bodies had been found in 72% of joints affected by rheumatoid arthritis after aspiration and lavage of syno-

vial fluid [2]. These materials could occur adjunctive to inflamed synovium, in the bursa [3], and around tendon sheaths [4], as well as in the pleural fluid of patients with rheumatoid arthritis [7]. They have also been reported in patients with juvenile arthritis [8], seronegative spondy-loarthritis [2], and osteoarthritis [2]. In the tuberculous

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arthritis and bursitis, it had been also often combined with rice bodies [5,6]. Rice bodies have been found in var-ious joints including shoulder, knee, wrist, and elbow [2]. MRI is a helpful diagnostic tool for rice bodies in the

synovial space and bursa ahead to operation. The MRI features of rice bodies are described as iso- or hypo-in-tense on T1-weighted and T2-weighted images. They are difficult to distinguish from bursal and synovial fluid on T1-weighted images, and a honeycomb-like pattern could be seen from the border of each body that is distinguished from the surrounding fluid on T2-weighted images, as shown in our report [9]. These appearances are not spe-cific findings of rice bodies, and they have to be differ-entiated from various benign synovial proliferative dis-orders, including chronic synovial proliferation, pig-mented villonodular synovitis, and synovial osteochon-dromatosis [9,10]. The etiology of rice bodies is not fully understood, but

they might originate from microinfarction of the syno-vium due to chronic inflammation [10]. Microscopic find-ings of rice bodies had shown an amorphous core sur-rounded by thin fibrin, and the core compositions were similar to those of inflamed synovium including types I, II, and V collagen and microvasculature [10]. Thus, float-ing materials might originate from proliferative syno-vium due to chronic inflammation. However, rice bodies had been rarely reported in the

joint with nonspecific synovitis as shown in Table 1. Several cases with rice bodies of the wrist joints and flexor tendon sheath in the absence of rheumatic disease or tu-berculosis have been reported, and these might be caused by overuse because they usually occurred on the patient’s dominant side [11]. And two cases of rice bodies in the knee joint with nonspecific synovitis have been reported, and both patients had no signs or laboratory findings of rheumatoid arthritis or infection [12,13]. And pediatrics also had rice bodies in knee and shoulder joints without definite inflammatory articular diseases [13,14]. All cas-es with idiopathic rice bodies had been accompanied with synovitis or tenosynovitis and any symptoms had not been recurred after only tenosynovectomy. Rice bodies without any inflammatory signs in the joint have not been previously reported. In our report, erythrocyte sed-imentation rate (ESR) and C-reactive protein (CRP) were within normal range, and no definite clinical features re-flecting inflammation such as tenderness or joint warmth were noted. Results of culture and PCR for tuberculosis and NTM were negative, and all ligaments and menisci

were intact. Furthermore, arthroscopic finding and path-ology of the synovium showed clean synovium without definite inflammatory cells infiltrates. Based on our case and literature reviews, we have to

check immunologic markers including rheumatoid factor (RF), anti-citrullinated protein antibody (ACPA), an-ti-nuclear antibodies (ANA) and HLA B27 and culture studies when rice bodies in the joint space are suspected in ultrasonography and MRI. Idiopathic rice bodies with nonspecific tenosynovitis could be clearly cured by tenosynovectomy. And idiopathic rice bodies without any inflammatory reaction also cloud be cured by surgical re-moval for relieving symptoms without additional medical treatments.

SUMMARY

Rice bodies were commonly detected in the synovial space in patients with rheumatoid arthritis or tuber-culosis and could often be found in the bursa and around tendon sheaths. The etiology of rice bodies had not been clearly understood, but they might be formed from chron-ic inflammation. However, we reported that massive rice bodies in the suprapatellar space were founded without any evidence of synovitis in the knee joint. Therefore, the pathogenesis of rice bodies must be studied in addition to inflammation in the future.

CONFLICT OF INTEREST

No potential conflict of interest relevant to this article was reported.

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