Sarcoidosis Following Hematopoietic Stem Cell Transplantation: Clinical Characteristics and HLA Associations

Pathogenetic Mechanisms Linking Sarcoidosis to Lymphoma

Sarcoidosis and lymphoma share immunopathological characteristics that suggest a complex, interconnected relationship. This article examines the multi-faceted mechanisms linking sarcoidosis to lymphoma, a phenomenon called sarcoidosis-lymphoma syndrome (SLS). SLS is hard to diagnose, requiring distinct criteria and imaging to differentiate overlapping features and histological differences. The co-occurrence of these diseases may be explained by genetic predispositions, immune dysregulation, and environmental factors that enhance malignancy risk. In active sarcoidosis, chronic inflammation and granuloma formation induce the production of cytokines that can contribute to lymphoma development. The role of macrophage polarization is also discussed. Immunosuppressive treatment prescribed in sarcoidosis patients, particularly corticosteroids and biological agents, may increase the susceptibility to lymphoproliferative malignancies. These common mechanisms emphasize the need for vigilant monitoring of lymphoma in patients with sarcoidosis, as this granulomatous disease can mimic and promote the development of lymphoma.

An Unusual Case of Hypercalcemia Due to Graft-Versus-Host Disease

Background/Objective

Hypercalcemia is a common disorder with a wide differential and is most commonly related to malignancy and hyperparathyroidism. Hypercalcemia is a rarely reported consequence of graft-versus-host disease (GVHD) and may be related to a granulomatous manifestation of the common stem cell transplantation procedure.

Case Report

A 67-year-old woman with a history of allogenic stem cell transplantation due to myelodysplastic syndrome presented to the bone marrow transplant clinic with dysphagia, muscle aches, and rash. She was found to have an extremely increased calcium and 1,25-dihydroxyvitamin D levels, which were ultimately corrected with administration of steroids and zoledronic acid.

Discussion

While uncommon, granulomatous disease can lead to hypercalcemia via the activation of 1α-hydroxylase within macrophages, which, in turn, activates 1,25-dihydroxyvitamin D leading to an increased serum calcium level. GVHD is a common, variably presenting complication of bone marrow transplantation. Granulomatous processes related to GVHD may mediate hypercalcemia in patients with both increased calcium and 1,25-dihydroxyvitamin D levels.

Conclusion

This is a rare cause of calcitriol-mediated hypercalcemia associated with GVHD. There have been cases of granulomas associated with GVHD, and this could potentially lead to ectopic production of calcitriol. We deemed GVHD to be a likely cause of the patient's calcitriol-mediated hypercalcemia because we did not find another etiology that fit the clinical findings. Physician awareness of this complication and the appropriate workup will allow future researchers to properly elucidate the etiology of this rare complication.