Incidental Findings of Acute Myeloid Leukemia in Sjögren's Syndrome Detected by Nuclear Medicine Techniques

Sjögren's syndrome is one of the most common chronic inflammatory autoimmune diseases primarily involving the exocrine glands, which affects mostly females in the fourth decade of life.[1] A 46-year-old female with Sjögren's syndrome previously treated with corticosteroids underwent bone scintigraphy for suspicious humeral osteonecrosis. Avascular osteonecrosis is a common complication observed in autoimmune disease patients after corticosteroid therapy.[2] Blood pool images [Figure 1a] showed slight increased distribution of technetium 99m-hydroxydiphosphonate in the head of the left humerus. Delayed images [Figure 1b], performed 3 h after the radiotracer administration, confirmed intense uptake of the left humerus, and suggestive for osteonecrosis. Nevertheless, images also revealed an ill-defined uptake in the humeral diaphysis, ribs, and spine. Whole-body bone scan [Figure 1c] showed multiple sites of heterogeneous radiotracer distribution throughout the skeletal, especially involving the skull, right sacroiliac region, left iliac wing, left femur, and tibia diaphysis.

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Figure 1

dual-phase bone scan (1a: blood pool images; 1b delayed images; 1c total body delayed images) showed increased distribution of 99m-hydroxydiphosphonate in the head of the left homerus and multiple sites of heterogeneous uptake throughout the skeletal. 18F-FDG PET/CT (1d: maximum intensity projection; 1e-h: axial fused 18F-FDG PET/CT) confirmed multiple sites of uptake, subsequently revealed to be localizations of acute myeloid leukemia

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Therefore, a lymphoproliferative disorder was suspected, also based on high levels of lactate dehydrogenase (2193 U/l), C-reactive protein (670 mg/L), erythrocyte sedimentation rate (97 mm/h), as well as white blood cells (16,83 × 10³/μl) and increased number of immature elements of the myeloid series in the peripheral blood. Platelets (218 × 10³/μl) and hemoglobin (11.6 g/dl) were within normality ranges. Indeed, Sjögren's syndrome can be associated with tumors, mostly lymphoma and occasionally T-cell leukemia/lymphoma, although the exact pathogenesis is still under debate.[23] F-18 fluorodeoxyglucose positron-emission tomography/computed tomography (18F-FDG PET/CT) has an established role in the diagnostic algorithm of patients with suspicious lymphoproliferative disorders, as well as in in detecting uncommon disease localizations and in response to treatment assessment.[45]

Thus, 18F-FDG PET/CT was performed. Maximum intensity projection image [Figure 1d] and axial fused 18F-FDG PET/CT [Figure 1e-h] confirmed the humeral osteonecrosis (black arrow) and diffusely increased and heterogeneous bone marrow activity (red square brackets and red arrows). In addition, 18F-FDG-avid soft tissue nodules were detected in the right scapular region, right axilla, and right thigh (arrowheads). Finally, the results of bone marrow biopsy demonstrated acute myeloid leukemia, a hematologic malignancy characterized by the clonal expansion of myeloid blasts in the peripheral blood and bone marrow. Likewise, skin nodule biopsy confirmed infiltration by malignant cells.

This case describes a rare acute myeloid leukemia in Sjögren's syndrome with associated humeral osteonecrosis, based on two-phase bone scan and 18F-FDG PET/CT findings. Although in our case, we did not completely discriminate osteonecrosis whether secondary to corticosteroids treatment or to leukemia, progressive skeletal symptoms in young patients may hide hematologic disease; therefore, a critical review of bone scan in such cases may help in the early settlement of diagnosis.[67] Moreover, our case highlights that nuclear medicine could have an important role in identifying possible localizations of malignant disease in Sjögren's syndrome, which may drive biopsy and subsequent clinical management.