Please cite this article in press as: Bouayed K, et al. Lipoma arborescens: A rare cause of bilateral pseudo-arthritis of the knee in children.
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Letter to the Editor
Lipoma arborescens: A rare cause of bilateral pseudo-arthritis of the knee in children
a r t i c l e i n f o
Keywords:
Lipomaarborescens Children
Knee
Bilateraldistribution
Lipoma arborescens is a rare and benign intra-articular tumor in which a frond-like proliferation of mature adipose cells replaces the synovial tissue. Most cases are unilateral. We report an unusual case in which both knees were affected.
A 13-year-old female presented with a 1-year history of swelling and pain in both knees. The knees were swollen, with a pos- itive patellar tap test. The erythrocyte sedimentation rate was elevated to 45 mm/h. Juvenile idiopathic arthritis was thought to be the most likely explanation to this chronic inflammatory oligoarthritis. Findings were negative from assays of antinuclear antibodies, rheumatoid factors, and anti-citrullinated protein anti- bodies. Indomethacin 3 mg/kg/d and methotrexate 25 mg/week were initiated. The symptoms persisted 1 year later. Joint aspira- tion failed to recover any material. Soft tissue thickening was seen on radiographs. Magnetic resonance imaging (MRI) findings were
Fig.1. Magneticresonanceimagingoftheknee,axialandsagittalviews:frond-likesynovialproliferationinthesupra-patellarbursa.
consistent with bilateral lipoma arborescens of the supra-patellar bursae (Fig. 1). A synovial biopsy specimen appeared hypertrophic, with a multilobulated architecture. Under the microscope, fatty frond-like projections were seen, with a normal or hyperplastic synoviocyte lining and sheets of mature adipocytes infiltrating the underlying tissue. After 5 months, the effusion in the right knee seemed to have resolved and the persistent swelling of the left knee was not associated with any noticeable functional impairment.
Lipoma arborescens is a rare condition that may occur either in isolation or in association with another joint disease [1,2]. The cause is unknown, and both a reactive mechanism and a primary proliferative process have been suggested [3,4]. Adults and males are predominantly affected, with a peak between 30 and 50 years of age. The youngest patient described to date was 9 years of age [3]. Although no joint is exempt, the knee is the main target. Most cases involve a single joint. A bilateral distribution occurs in 20%
of cases and suggests underlying osteoarthritis [4]. Imaging studies showed no evidence of osteoarthritis in our patient. The symptoms set in gradually and consist of swelling, pain and, in some cases, motion range limitation. This clinical picture often suggests juve- nile idiopathic arthritis, as occurred in our patient. Laboratory tests are usually normal [5]. Soft tissue thickening is visible on standard radiographs. By ultrasonography, intraarticular images of increased echogenicity similar to that of subcutaneous fat tissue are seen.
MRI is the diagnostic investigation of choice. The strong fatty signal on all sequences except STIR confirms the diagnosis and rules out differential diagnoses including villonodular synovitis (absence of
http://dx.doi.org/10.1016/j.jbspin.2016.11.003
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Please cite this article in press as: Bouayed K, et al. Lipoma arborescens: A rare cause of bilateral pseudo-arthritis of the knee in children.
Joint Bone Spine (2017), http://dx.doi.org/10.1016/j.jbspin.2016.11.003
ARTICLE IN PRESS
G Model
BONSOI-4496; No.ofPages2
2 LettertotheEditor/JointBoneSpinexxx(2017)xxx–xxx
hemosiderin deposits), synovial lipoma, synovial chondromatosis, rheumatoid arthritis, and synovial hemangioma [4,6–9]. The gross examination shows a yellow villous tumor and, under the micro- scopie, the villi are seen to be filled with mature adipose cells. The treatment of choice is synovectomy performed arthroscopically or by open surgery depending on the size of the tumor [6]. Other treat- ments such as yttrium-90 radiation synovectomy and osmic acid synovectomy have produced satisfactory outcomes [4]. In addition, early synovectomy may prevent the otherwise inevitable progres- sion to degenerative joint disease [10]. Surgical treatment may therefore be warranted in our patient.
Disclosure of interest
The authors declare that they have no competing interest.
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Kenza Bouayed
a,∗Abdelmounim Cherqaoui
bSiham Salam
cMehdi Karkouri
dNabiha Mikou
aa
Service de pédiatrie générale et rhumatologique, hôpital d’Enfants A. Harouchi, université de médecine Hassan 2, CHU Ibn Rochd, 1, rue des Hôpitaux, 20450 Casablanca, Morocco
b
Service d’orthopédie pédiatrique, hôpital d’Enfants A. Harouchi, université de Médecine Hassan 2, CHU Ibn Rochd, 20450 Casablanca, Morocco
c
Service de radiologie pédiatrique, hôpital d’Enfants A. Harouchi, université de médecine Hassan 2, CHU Ibn Rochd, 20450 Casablanca, Morocco
d
Service d’anathomo-pathologie, université de Médecine Hassan 2, CHU Ibn Rochd, 20450 Casablanca, Morocco
∗
