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Introduction: Renal phospholipidosis describes the accumulation of phospholipids in the lysosomes of kidney cells, in particular podocytes. Originally, this was described primarily in the context of the lysosomal storage disorder Fabry disease. It is now known that a variety of drugs can lead to the accumulation of lysosomal phospholipids. Case Presentation: We present the case of a 69-year-old female patient suffering chronic kidney disease and systemic lupus erythematosus who underwent a kidney biopsy because of a further increase in serum creatinine levels. There was no evidence of lupus nephritis, but electron microscopy showed zebra bodies as a morphological sign of phospholipidosis. This was most likely drug-induced after 25 years of continuous medication with hydroxychloroquine. A renal biopsy 2 years and 6 months earlier, when the renal function of the patient was distinctively better, showed no signs of renal phospholipidosis. Afterward, medication with hydroxychloroquine was discontinued, and renal function parameters remained stable in the 1-year course. Conclusion: This case raises the question of how severely impaired renal function affects the risk of hydroxychloroquine-induced renal phospholipidosis and underlines that hydroxychloroquine should be administered with caution in patients with kidney insufficiency. Moreover, we provide a review of the causes of renal phospholipidosis, which have been described in the literature and give an overview of possible differential diagnoses in cases with histologically proven phospholipidosis in renal biopsies.

Immunotactoid glomerulopathy (ITG) occurs infrequently and is characterized by organized IgG containing deposits. It most usually manifests as a concomitant disease of a broad spectrum of oncologic entities. We here present an exceptional case of ITG without glomerular light chain restriction secondary to a IgM kappa type monoclonal gammopathy of undetermined significance. Due to nephrotic syndrome and deterioration of kidney function a rituximab monotherapy was initiated without targeting the plasmacellular augmentation, which was confirmed as the underlying process. The treatment led to a long-term improvement of proteinuria and stabilization of glomerular filtration rate. Its therapeutic effect has to be attributed to immunomodulatory capacities and targeting of podocytes rather than to be interpreted as directed against a bone marrow or glomerular clone. We conclude that rituximab therapy may be a valuable part of the therapeutic options in ITG irrespective of the underlying oncologic entity.