Iron deposits in the knee joints of a thalassemic patient
A 45-year-old white man with β-thalassemia major was referred for MRI of the left knee due to prominent non-traumatic chronic medial and lateral pain (past 1–2 years), as well as partial locking and restriction in the range of motion. Neither previous nor recent traumatic knee injury nor other suspicious events were reported. The patient had been undergoing regular blood transfusions twice a month maintaining a hemoglobin level of about 9.5 mg/dl and a ferritin level of 3000 ng/mL. The patient reported receiving chelation therapy with only oral deferiprone for the past 13 years at a dose of 75 mg/kg/day. Occasional chelation with desferioxamine was also used during the same time period. T2* measurements from previous MRI examinations on heart and liver are presented in Table . It was evident from the decreasing T2* measurements of heart and liver, that there was progressive increase in the degree of iron deposits in the above two organs in parallel with clinical observations of poor adherence to chelation therapy compatible with high levels of plasma ferritin. Following regular assessment, the patient underwent MRI of the left knee. Subsequent MR scanning of the right knee was also performed for comparison purposes. Written informed consent was obtained from the patient for publication of this manuscript and accompanying images.\nMRI was performed with a 3.0 Tesla scanner (Achieva, Philips Medical Systems, Best, The Netherlands) to assess arthropathy including potential iron deposits in the knee joints. We used the built-in quadrature radiofrequency (RF) body coil and a phased array 8-channel knee coil for proton excitation and signal detection, respectively. MRI scanning protocol included several multislice pulse sequences routinely performed for morphological imaging (in each case, 28 slices were acquired with a field-of-view of 170 mm, a section thickness of 2.8 mm, and a pixel size of 0.6 × 0.7 mm); T1-weighted (T1-w) (repetition time [TR], 674 ms; echo time [TE], 18 ms; total scan time [ST], 2.5 min) turbo spin echo (TSE) in the sagittal plane; T2*-weighted (T2*-w) (TR, 575 ms; TE, 12 ms; ST, 2.4 min) gradient recalled echo (GRE) in the axial plane; proton density-weighted (PD-w) (TR, 2342 ms; TE, 35 ms; ST, 2.9 min) TSE with spectral fat suppression in the coronal and axial planes. Three-dimensional (3D) susceptibility weighted imaging (SWI) and ultra short echo time (UTE) GRE pulse sequences were also prescribed in the axial plane. The former utilizes an echo-shifting technique that allows the employment of relatively long echo times (TE, 21 ms) in a time-efficient way (TR, 15 ms; ST, 1.5 min for 100 slices with an acquisition resolution of 1 × 1× 2 mm). The latter uses a radial data sampling technique achieving an ultra short TE of 14 μs (TR, 7.5 ms; ST, 9.8 min; 144 slices; 1 mm3 acquisition voxel size). The sequence used for quantitative T2 measurements was also prescribed in the sagittal plane. A single-slice (acquisition voxel size of 0.5 × 0.5 × 5.0 mm) Carr Purcel Meibomm Gill (CPMG) spin echo sequence employing 16 equidistant echoes, a short echo spacing of 6 ms and a TR of 2s was used (ST, 5.7 min).\nLeft knee MR images revealed several pathological findings compatible with the prominent clinical symptomatology. The imaging findings included a flap tear of the medial meniscus with a displaced meniscal fragment in the medial intercondylar notch (Fig. ). In addition, osteoarthritis was noted in the medial joint compartment with marked attenuation of the articular cartilage, reactive subcortical bone marrow edema in the medial tibial plateau, and minimal subcortical cystic changes (Fig. ). Furthermore, there was mild attenuation of the patellar cartilage indicating chondromalacia patellae grade II. Foci of iron deposits were identified macroscopically within the supra-patellar pouch right above the superior pole of the patellae and also in contact with the patellae cartilage at the upper pole, as well as within the Hoffa's fat pad in contact with the patellae cartilage in its inferior pole and in the cartilage surface over the trochlea (Fig. a). Finally, iron deposits were also noted along the surface of the medial plica in the supra-patellar pouch. The iron deposits were detected as low signals intensity foci in all MRI sequences used. However, iron deposits were less conspicuous on the T1-w and PD-w sequences, with particular signal loss on gradient echo (Fig. B). During the above study we also noticed further exaggeration of the signal loss on the SWI and UTE sequences (Fig. ). In Table we present mean T2 measurements for regions of interest prescribed in different areas of the cartilage in the left knee. The T2 measurement of normal Hoffa's fat pad was 215 ms (18.8 SD), while in Hoffas fat pad with iron deposits T2 measurement was 54.8 ms (11 SD) and in the supra-patellar pouch with iron deposits T2 was 51.1 ms (4.4 SD), respectively. Such findings indicate iron deposits in the above regions with decreased T2 measurements.\nMRI of the right knee was also performed mainly for comparison purposes. Iron deposits were also noted in the right knee (Fig. ). Iron deposits were noted in contact with the inferior pole of the patellar cartilage, as well as in contact with the anterior articular surface of the lateral femoral condyle.\nFollowing MRI studies, the patient underwent an arthroscopy of the left knee in order to explore the pathological imaging findings and repair the meniscal tear. Biopsy of the synovium showed edema of the basal membrane with papillary morphology and hemosiderin deposits. Histiocytes with hemosiderin moieties were also noted along with hyperplastic serous cells.