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January 2009 Case of the Month
Compiled by: RakeshH. Patel, M.D.
History: 73-year-old female with hip pain
Exam: MR Hip without Contrast
Findings & Images:
Figure 1(coronal T1) and Figure 2 (coronal PD SPIR), as well as Figure 3 (axial T1) and Figure 4 (axial PD SPIR), show abnormal diffuse and homogenous symmetric decreased marrow signal on the T1-weighted sequences and abnormal diffuse and homogenous increased marrow signal on the fluid-sensitive sequences.
Hepatosplenomegaly (arrows) is an important secondary finding.
Figure 1
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Figure 2
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Figure 3
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Figure 4
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Diagnosis: Polycythemia Vera
Discussion: Polycythemia Vera is an idiopathic disorder characterized by an increase in hemoglobin concentration and red-blood-cell mass, and represents one of the benign myeloproliferative disorders (agnogenic myeloid metaplasia, reconversion, essential thrombocytopenia, and mastocytosis are among the others). PV occurs in about 5 out of 1,000,000 persons, with an average age of 60 at diagnosis. Extramedullary hematopoeisis occurs in the liver and spleen.
Hepatosplenomegaly, which is sometimes massive, is found in all cases.
Since red (hematopoietic/active) to yellow (fatty/inactive) marrow conversion is complete in adults by 25 years of age, marrow infiltration is more likely to be seen in the axial skeleton, pelvis, and proximal femurs. In children, marrow involvement is more likely seen in the metaphysis with diaphyseal or epiphyseal extension. Reconversion of yellow to red marrow is triggered by the body’s demand for increased blood-cell production (examples include obesity, smokers, anemias, sports, high altitudes, granulocyte colony-stimulating factor related to chemotherapy, and marrow-proliferative disorders). Normal red marrow demonstrates T1 signal that is equal to or higher than adjacent muscle or intervertebral disks.
Secondary causes of myelofibrosis include metastatic carcinoma, leukemia, lymphomas, TB, Gaucher’s disease, Paget’s disease, irradiation, and toxin exposure. Superimposed osteonecrosis is seen with sickle-cell anemia, Waldenstrom’s macroglobulinemia, Gaucher’s, and steroid treatment.
Although other marrow-infiltrating disease processes, such as multiple myeloma and metastatic disease (with patchy asymmetric heterogenous variable signal), can be separated from chronic leukemias, differentiation between various myeloproliferative disorders is difficult with imaging alone. More importantly, proliferation of abnormal cells may be indistinguishable from normal red marrow early in the disease process secondary to low tumor burden, especially in 10-20% of patients with multiple myeloma and leukemia. Hence, laboratory data and blood sample analysis as well as marrow sampling are needed for definitive diagnosis.
MR Findings (as above): Look for abnormal signal intensity, abnormal signal distribution, or both. Others as below:
- Aplastic anemia/radiation (diffuse T1 marrow pallor)
- Gaucher’s (low signal, infarcts, spares epiphyses)
- Hemosiderosis (very low T2 signal)
- Leukemia (intermediate T1 signal, spares epiphyses)
- Lymphoma (intermediate smooth T1 and T2 signal)
- Myeloid metaplasia (gray T1 and T2)
- Myeloma (bright nodules on STIR imaging, gray signal, fractures, hollow vertebral sign)
- Osteoporosis (exaggerated trabeculae and low T1 and T1 signal)
- Post-transplant (heterogenous marrow)
- Prostate cancer (very low T1 and T2)
- Transient osteoedema (homogenous lateral femoral head hypo T1 and hyper T2 signal)
Differential Diagnoses:
- Benign: Agnogenic myeloid metaplasia, reconversion, mastocytosis, myelodysplastic syndrome, essential thrombocytopenia
- Malignant: Chronic myelogenous leukemia, lymphoma, multiple myeloma, amyloidosis, Waldenstrom’s macroglobulinemia
- Hemoglobinopathies
- Felty’s syndrome
References:
1. Soller, DW. Magnetic Resonance Imaging in Orthopaedics and Sports Medicine. 3rd Ed., Vol. 2, Baltimore, MD: Wolters Kluwer-Lippincott Williams and Wilkins, 2007.
2. KaplanP, Helms CA, Dussault R, Anderson MW, and Major NM.Musculoskeletal MRI . Philadelphia, PA: WB Saunders, 2001.
3. Pomeranz, SJ, et al. Gamuts and Pearlsin MRI & Orthopedics. Cincinnati, OH: MRI-EFI Publications, 1997. |
