Quantification of bone involvement in Gaucher disease: MR imaging bone marrow burden score as an alternative to Dixon quantitative chemical shift MR imaging--initial experience

PURPOSE: To develop a semiquantitative magnetic resonance (MR) imaging bone marrow burden (BMB) score with inclusion of both axial and peripheral bone marrow in Gaucher disease as an alternative to MR imaging with the Dixon quantitative chemical shift imaging (QCSI) technique. MATERIALS AND METHODS: Two experienced musculoskeletal radiologists with no experience in evaluating Gaucher disease blindly analyzed MR images of lumbar spines and femora. Interobserver and intraobserver variability were tested. In addition, the BMB score was determined as a parameter to evaluate bone marrow response to enzyme supplementation therapy. Finally, the BMB score was compared with fat fraction measurements obtained with Dixon QCSI. Differences between groups were analyzed by using the nonparametric Mann-Whitney test. A P value of less than.05 was considered to represent significance. Correlation was calculated by using two-tailed nonparametric rank correlation (Spearman rho). RESULTS: In 30 patients (mean age, 39.3 years; age range, 12-71 years) the mean fat fraction was 0.20 (range, 0.08-0.40). The BMB score range was 3-13 points. A significant correlation was found between the two observers when using BMB (rho = 0.91, P <.001). The intraobserver variation showed a significant correlation (rho = 0.99, P <.001). There was a significant correlation between BMB and QCSI (rho = -0.78, P <.001). Although BMB was less sensitive than Dixon QCSI, it showed enough sensitivity to allow detection of bone marrow response to enzyme supplementation therapy. CONCLUSION: BMB is a reproducible semiquantitative scoring system that is easy to use. It combines MR imaging of both axial and peripheral bone marrow and shows a significant correlation with QCSI.     

Lymphocyte subsets in normal bone marrow

Bone marrow aspirates and biopsies from ten normal donors were stained directly with monoclonal antibodies specific for lymphocyte, monocyte, and myeloid antigens, and were analyzed by flow cytometry. To avoid cell loss, lymphocytes were not specifically isolated prior to staining. T cells comprised 46% of aspirate lymphocytes and 22% of biopsy lymphocytes. Further, the Leu-3:Leu-2 ratio of bone marrow T cells was below 1.0. B cells comprised 8% to 11% of bone marrow lymphocytes in both aspirates and biopsies, and there was a substantial percentage of cells in the lymphocyte window that was negative for all B and T cell markers. The lymphocyte window had very little myeloid contamination; however, when the myeloid window was examined, staining was greater than 90%.     

Bilateral adrenal tumours in primary aldosteronism: localization of a unilateral aldosteronoma by dexamethasone suppression scan

In a patient with primary aldosteronism, in which the postural endocrine tests suggested the presence of an aldosteronoma rather than hyperplasia, bilateral adrenal tumours were found by computer tomography. Adrenal scintigraphy using 6-131I-iodomethyl-19-norcholesterol (NP59) during dexamethasone suppression showed early unilateral adrenal visualization on the left side. After removal of the left adrenal gland, which contained a 2 x 2 x 2 cm adenoma, the blood pressure and aldosterone levels returned to normal. A CT-scan, performed 1 year after the pre-operative CT-scan, showed no change in size of the right adrenal tumour, consistent with a non-functioning adenoma. In this patient, the NP59 scan adequately distinguished a non-functioning from an aldosterone-producing adrenal tumour.     

Phase 1 immunolymphoscintigraphy with an In-111-labeled antimelanoma monoclonal antibody

A phase 1 study was conducted using a monoclonal antimelanoma antibody-DTPA conjugate labeled with indium-111, for immunolymphoscintigraphy in patients with metastatic melanoma. The imaging agent, labeled with 1 mCi (37 MBq) In-111, was administered as an interstitial interdigital injection to six patients scheduled to undergo lymph node dissection for suspected metastatic malignant melanoma. No adverse effects were observed in any of the patients either during or after the infusion as determined by clinical and laboratory parameters. Antibodies to the murine immunoglobulin were produced in some patients. Regional lymph nodes were visualized whether tumor-bearing or not, and light microscopic autoradiography showed In-111 activity associated with histiocytes. One of two patients harboring both tumor-bearing and tumor-free lymph nodes exhibited preferential localization in tumor-bearing nodes. The authors conclude that this study demonstrates safety of the radiopharmaceutical and that further study is needed to improve its usefulness for diagnosis of lymph node metastases.     

Identification and use of biomarkers in Gaucher disease and other lysosomal storage diseases

The value of biomarkers in the clinical management of lysosomal storage diseases is best illustrated by the present use of plasma chitotriosidase levels in the diagnosis and monitoring of Gaucher disease. The enzyme chitotriosidase is specifically produced and secreted by the pathological storage macrophages (Gaucher cells). Plasma chitotriosidase levels are elevated on average 1000-fold in symptomatic patients with Gaucher disease and reflect the body burden on storage cells. Changes in plasma chitotriosidase reflect changes in clinical symptoms. Monitoring of plasma chitotriosidase levels is nowadays commonly used in decision making regarding initiation and optimization of costly therapeutic interventions (enzyme replacement therapy or substrate reduction therapy). A novel substrate has been developed that further facilitates the measurement of chitotriosidase in plasma samples. Moreover, an alternative Gaucher-cell marker, CCL18, has been very recently identified and can also be employed to monitor the disease, particularly in those patients lacking chitotriosidase due to a genetic mutation. There is a need for comparable surrogate markers for other lysosomal storage diseases and the search for such molecules is an area of intense investigation. Conclusion: The use of biomarkers can provide valuable insight into the molecular pathogenesis of LSDs, such as Gaucher disease and Fabry disease.