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JCR: Journal of Clinical Rheumatology:
doi: 10.1097/RHU.0b013e3181b1e4fb
Case Report

Polyarticular Lipoma Arborescens With Inflammatory Synovitis

Santiago, Mittermayer MD*; Passos, Antonio Sérgio MD†; Medeiros, Antonio Felipe MD‡; Sá, Daniel MD§; Correia Silva, Tânia Maria MD¶; Fernandes, João Luiz MD§

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From the *Department of Rheumatology, Escola Bahiana de Medicina e Saúde Pública (EBMSP), Salvador, Brazil; †Department of Ortopedic surgery; ‡Escola Bahiana de Medicina e Saúde Pública (EBMSP), Salvador, Brazil; §Image Memorial, Salvador, Brazil; and ¶Oswaldo Cruz Foundation, Salvador, Brazil.

Supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (to M.S.) and FIDEPS.

Correspondence: Mittermayer B. Santiago, Praça Conselheiro Almeida Couto, 500, Nazaré, Salvador, CEP 40000, Bahia, Brazil. E-mail:

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Lipoma arborescens is a rare clinical condition characterized by mono or biarticular involvement of large joints, such as knees, hips, ankles, elbows, and shoulders. The aim of this case report is to describe an unusual case of lipoma arborescens affecting multiple large joints, mimicking rheumatoid arthritis. The patient, a 29-year-old woman had a history of intermittent arthritis of the wrists, knees, and ankles for at least 12 years. With the diagnosis of rheumatoid arthritis she had been on methotrexate (7.5 mg/wk) for the last 6 months along with different nonsteroidal anti-inflammatory drugs, without benefit. On physical examination a discreet joint swelling of the knees without effusion, gluteal muscle atrophy, and limited hip movements were observed. Laboratory tests presented normal acute phase reactants of inflammation as well as the rheumatoid factor, CK, and negative results for antinuclear, anti-DNA, anti-SSA/Ro, and anti-CCP (ELISA) antibodies. Magnetic resonance imaging of the knees and hips showed articular effusion and synovitis, and a pattern of lipoma arborescens. The histopathologic study confirmed the diagnosis. Knee arthroscopic synovectomy brought some improvement to joint mobility and pain.

Although rare, this condition must be remembered in the presence of inflammatory arthropathy, particularly in the absence of response to clinical treatment, and absence of rheumatoid factor and anti-CCP antibodies, since the therapeutic strategy is radically different.

Lipoma arborescens (LA) is a rare clinical condition that mimics an inflammatory state and affects mainly large joints, such as knees and hips, but also affecting ankles,1,2 elbows,3 and shoulders.4 Its etiology is unknown and the histopathologic picture is a hypertrophic fat infiltration of the synovium with proliferation of capillaries, corresponding to a “lipoma-like” lesion in which the subsynovial connective tissue is infiltrated by mature adipocytes, often associated with scattered inflammatory cells.5 An increasing number of cases have recently been described, attributable to the widespread use of magnetic resonance imaging (MRI) as a diagnostic tool for articular disorders. Clinically, it presents as a mono or biarticular inflammation, sometimes painless, following an intermittent pattern. Rarely, it may affect more than 2 joints simultaneously.5,6

The aim of this case report is to describe an unusual case of LA affecting multiple large joints, mimicking rheumatoid arthritis (RA). To the best of our knowledge this is the fourth case of this type reported in the published data.

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The patient was a 29-year-old woman with a history of intermittent arthritis of the wrists, knees, and ankles for at least 12 years. She also complained of limitation in the movements of her hips. With the diagnosis of RA she had been on methotrexate (7.5 mg/wk) for the last 6 months along with nonsteroidal anti-inflammatory drugs, such as diclofenac, piroxicam, and etoricoxib without benefit. On physical examination she presented a good general state, with blood pressure 120/80 mm Hg, with no alteration in the cardiorespiratory system and no hepatosplenomegaly. Musculoskeletal examination showed a discreet joint swelling of the knees without overt effusion, gluteal muscle atrophy, and limited hip movements. Laboratory tests presented hemoglobin of 12.6 g/dL; white blood cell count 5500 cells/mm3; normal glycemia, cholesterol, creatinine, and hepatic enzymes. Acute phase reactants of inflammation, such as erythrocyte sedimentation rate and C-reactive protein were normal. Furthermore, antinuclear (ANA), anti-DNA, anti-SSA/Ro, and anti-CCP antibodies as well as rheumatoid factor were negative. Radiographs of the joints presented diminished articular space in the hips joints. Bone scintillography was normal. MRI of the knees and hips showed moderate articular effusion, synovitis, and a pattern of lipoma arborescens (Figs. 1 and 2). The patient was submitted to a knee arthroscopic synovectomy for both diagnostic and therapeutic purpose. This revealed an abundant diffuse mature adipose subsynovial infiltration with villous architecture (Fig. 3A) and a nonspecific chronic inflammation with intense fibrosis, inflammatory mononuclear cells infiltration, and synovial cell hyperplasia (Fig. 3B). There were no signs of fibrinoid necrosis, granuloma, or lymphoid follicles.

Figure 1
Figure 1
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Figure 2
Figure 2
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Figure 3
Figure 3
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As the knee synovectomy brought some improvement to joint mobility and pain, a similar procedure in the opposite knee has been planned. Presently, she is only on nonsteroidal anti-inflammatory drugs.

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Lipoma arborescens, also known as synovial lipomatosis is a rare, benign intra-articular lesion of unknown etiology, which more frequently involves the suprapatellar pouch of the knee. In the majority of cases, the involvement is monoarticular, although patients with bilaterally affected joints involvement of the hips, wrists, shoulders, ankles, and elbows has also been reported.4,7 The involvement of multiple joints in the same patient is an even rarer occurrence, with only a few cases published.5–7 Moreover, extensive extensor and flexor tendon sheath involvement in the hands and tendons around the ankles has also been described.1,5

The reason why the fat proliferation occurs is not completely known. Although it can occur without antecedents, sometimes it is preceded by a traumatic or inflammatory process. Accordingly, it has been suggested that chronic synovitis may be the precursor for LA.8 In contrast, the inflammation in the synovial tissue may be secondary to the trapping of fatty masses. In the present case, the involvement of multiple joints resembled RA, but the normal erythrocyte sedimentation rate, absence of rheumatoid factor and anti-CCP antibodies, as well as the lack of response to methotrexate therapy ruled out this possibility. As occurred in our case, Cil et al also described a child with LA of both knees, which had been erroneously diagnosed as oligoarticular juvenile rheumatoid arthritis.9 Besides the histopathologic findings of LA, our patient also had nonspecific mononuclear cells infiltration and synovial cell hyperplasia in the knee biopsy. Similar inflammatory synovitis in LA has been recently reported.10 Theoretically, this synovitis might be an opportunity to try a much more aggressive treatment of the inflammation to avoid joint damage.

LA is identified more frequently after the age of 50 years. However, as in the present case, whose joint manifestations began to present before the age of 20 years, Siva et al5 also described the case of a 35-year-old man with polyarticular LA, whose symptomatology had started at the age of 15 years. This early onset does not appear to define a tendency for polyarticular involvement, since monoarticular LA has been seen in children.11

The conventional radiologic study in LA is nonspecific, thus diminishment of the articular space seen in the hip join of our patient may be attributed to the secondary degenerative process throughout the long duration of her disease. This phenomenon has been observed in other cases of LA.10 Precise diagnosis of the disease is generally established by MRI of the affected joints. The main findings of MRI are: synovial mass with arborescent and fronded architecture, and sign of intensity similar to fat in all the sequences, in STIR (fat suppression) or in “spin-echo” sequences with fat saturation; artifacts of the “chemical-shift” type at the fat—liquid interface in the articular space; absence of nonfat soft tissue component and hemosiderin.5 These findings exclude other diseases with symptomatology and radiology similar to that of LA. Thus, the MR imaging shows a high accuracy in the identification and characterization of LA, and it can save invasive procedures.

Soler et al in a comprehensive review on the MRI characteristics of LA, suggested that there are 3 common morphologic patterns of presentation: multiple villous lipomatous synovial proliferations, isolated frond-like fat subsynovial mass, and mixed pattern.12 Our patient seems to fit the first type.

The recommended treatment for LA is open synovectomy. Arthroscopic synovectomy has also been indicated, with favorable outcome up to 2 years and is mainly indicated in patients with joint pain, limitation of movement and particularly when the proliferation is confined to the anterior knee compartment.13 The present report confirms the benefit of arthroscopic synovectomy for LA. In only 1 case described in the published data, there was recurrence of disease after surgery. Nevertheless, in patients without pain and no limitation of movement, a conservative treatment is still frequently indicated. Episodes of exacerbation due to the presence of effusion can be controlled with articular injection of corticosteroids. Radiosynovectomy with yttrium-90 colloid has also been successfully used. Erselcan et al injected 185 MBq of the substance together with 40 mg methylprednisolone in the right knee of a 36-year-old female patient with LA. A year after the application the patient had sustained clinical response and the improvement was confirmed by the MRI findings.14

In conclusion, LA affecting multiple joints although rare entity can mimic RA or early undifferentiated form of arthritis. This rare entity should be ruled out in arthritides that remain undifferentiated after conventional clinical, biochemical, plain radiographic evaluations, and lack of response to DMARDs. MRI due to its multiplanar capabilities and high contrast resolution allows correct evaluation of size and grade, accurate treatment planning, and effective follow-up.

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1. Babar SA, Sandison A, Mitchell AW. Synovial and tenosynovial lipoma arborescens of the ankle in an adult: a case report. Skeletal Radiol. 2008;37:75–77.

2. Huang GS, Lee HS, Hsu YC, et al. Tenosynovial lipoma arborescens of the ankle in a child. Skeletal Radiol. 2006;35:244–247.

3. Doyle AJ, Miller MV, French JG. Lipoma arborescens in the bicipital bursa of the elbow: MRI findings in two cases. Skeletal Radiol. 2002;31:656–660.

4. Pandey T, Alkhulaifi Y. Bilateral lipoma arborescens of the subdeltoid bursa. Australas Radiol. 2006;50:487–489.

5. Siva C, Brasington R, Totty W, et al. Synovial lipomatosis (lipoma arborescens) affecting multiple joints in a patient with congenital short bowel syndrome. J Rheumatol. 2002;29:1088–1092.

6. Bejia I, Younes M, Moussa A, et al. Lipoma arborescens affecting multiple joints. Skeletal Radiol. 2005;34:536–538.

7. Sumen Y, Ochi M, Soda Y, et al. Lipoma arborescens in bilateral knee joints. Arch Orthop Trauma Surg. 1998;117:105–107.

8. Oni DB, Oni G. Inflammatory synovitis due to underlying lipoma arborescens. Clin Rheumatol. 2008;27:1079.

9. Cil A, Atay OA, Aydingoz U, et al. Bilateral lipoma arborescens of the knee in a child: a case report. Knee Surg Sports Traumatol Arthrosc. 2005;13:463–467.

10. Ragab Y, Emad Y, Banakhar A. Inflammatory synovitis due to underlying lipoma arborescens (gadolinium-enhanced MRI features): report of two cases. Clin Rheumatol. 2007;26:1791–1794.

11. Nisolle JF, Boutsen Y, Legaye J, et al. Monoarticular chronic synovitis in a child. Br J Rheumatol. 1998;37:1243–1246.

12. Soler T, Rodriguez E, Bargiela A, et al. Lipoma arborescens of the knee: MR characteristics in 13 joints. J Comput Assist Tomogr. 1998;22:605–609.

13. Franco M, Puch JM, Carayon MJ, et al. Lipoma arborescens of the knee: report of a case managed by arthroscopic synovectomy. Joint Bone Spine. 2004;71:73–75.

14. Erselcan T, Bulut O, Bulut S, et al. Lipoma arborescens; successfully treated by yttrium-90 radiosynovectomy. Ann Nucl Med. 2003;17:593–596.

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This article has been cited 3 time(s).

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lipoma arborescens; arthritis; magnetic resonance imaging

© 2009 Lippincott Williams & Wilkins, Inc.

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