Effect of Osteocyte-Ablation on Inorganic Phosphate Metabolism: Analysis of Bone-Kidney-Gut Axis.

In response to kidney damage, osteocytes increase the production of several hormones critically involved in mineral metabolism. Recent studies suggest that osteocyte function is altered very early in the course of chronic kidney disease. In the present study, to clarify the role of osteocytes and the canalicular network in mineral homeostasis, we performed four experiments. In Experiment 1, we investigated renal and intestinal Pi handling in osteocyte-less (OCL) model mice [transgenic mice with the dentin matrix protein-1 promoter-driven diphtheria toxin (DT)-receptor that were injected with DT]. In Experiment 2, we administered granulocyte colony-stimulating factor to mice to disrupt the osteocyte canalicular network. In Experiment 3, we investigated the role of osteocytes in dietary Pi signaling. In Experiment 4, we analyzed gene expression level fluctuations in the intestine and liver by comparing mice fed a high Pi diet and OCL mice. Together, the findings of these experiments indicate that osteocyte ablation caused rapid renal Pi excretion (P < 0.01) before the plasma fibroblast growth factor 23 (FGF23) and parathyroid hormone (PTH) levels increased. At the same time, we observed a rapid suppression of renal Klotho (P < 0.01), type II sodium phosphate transporters Npt2a (P < 0.01) and Npt2c (P < 0.05), and an increase in intestinal Npt2b (P < 0.01) protein. In OCL mice, Pi excretion in feces was markedly reduced (P < 0.01). Together, these effects of osteocyte ablation are predicted to markedly increase intestinal Pi absorption (P < 0.01), thus suggesting that increased intestinal Pi absorption stimulates renal Pi excretion in OCL mice. In addition, the ablation of osteocytes and feeding of a high Pi diet affected FGF15/bile acid metabolism and controlled Npt2b expression. In conclusion, OCL mice exhibited increased renal Pi excretion due to enhanced intestinal Pi absorption. We discuss the role of FGF23-Klotho on renal and intestinal Pi metabolism in OCL mice.

Diffuse Large B-cell Lymphoma during Corticosteroid Therapy for TAFRO Syndrome.

Thrombocytopenia, anasarca, myelofibrosis, renal dysfunction and organomegaly (TAFRO) syndrome is a variant of Castleman's disease recently identified in Japan. A 73-year-old man was diagnosed with TAFRO syndrome according to clinical findings, and his symptoms improved after corticosteroid therapy. Ten months later, lymphadenopathy worsened during tapering of corticosteroids. Histological findings of abdominal lymph nodes showed diffuse large B-cell lymphoma. After 6 cycles of R-CHOP therapy, he has remained in sustained complete remission. This is a rare case of the development of malignant lymphoma during the treatment of TAFRO syndrome, which suggests an association between diffuse large B-cell lymphoma and TAFRO syndrome.

[Relapse in the nasal cavity of a patient with extranodal NK/T-cell lymphoma initially presenting as plantar subcutaneous tumor].

A 36-year-old woman complained of a mass on the sole of her foot in February 200X. She was diagnosed with extranodal NK/T-cell lymphoma, nasal type (ENKL) by skin biopsy. Because the lesion was localized on the subcutaneous tissue of the sole, she was treated with RT/2/3DeVIC, resulting in a complete response (CR). In March of the following year, PET/CT showed significant uptake and mucosal thickening in the right nasal cavity, and a mucosal biopsy confirmed ENKL infiltration. Because the lesion was localized in the nasal cavity, she was re-treated with RT/2/3DeVIC, with a focus on local control, and she achieved a second CR. She subsequently received allogeneic hematopoietic stem cell transplantation in the hope of preventing systemic relapse. She has remained in CR for four years since the transplantation. Our case suggests that allogeneic hematopoietic stem cell transplantation to be a potentially promising approach to curative treatment for recurrent ENKL in younger patients. As nasal lesions may subsequently appear during the course of primary non-nasal ENKL, ongoing meticulous evaluation for nasal lesions is important.

[Development of syndrome of inappropriate secretion of ADH and reversible posterior leukoencephalopathy during initial rituximab-CHOP therapy in a patient with diffuse large B-cell lymphoma].

A 61-year-old woman presented with a right mandibular tumor and was diagnosed with DLBCL clinical stage IIIA from the biopsy results of the tumor and CT examination. An initial rituximab was administrated a week after the first CHOP treatment. During the infusion of rituximab, she exhibited disorientation, seizure, and consciousness disturbance. Hyponatremia due to SIADH and hypertension were coincidentally observed. MRI revealed T2 and FLAIR hyperintense signals involving the bilateral occipital, parietal, frontal lobes and the cerebellum that were consistent with reversible posterior leukoencephalopathy syndrome (RPLS). Her consciousness level recovered in parallel with corrections in serum sodium levels and blood pressure. Although she presented with transient cortical blindness, all neurological abnormalities disappeared 40 hours after the occurrence of seizure. She received a further 7 cycles of CHOP followed by 7 cycles of rituximab treatment with no relapse of RPLS. After irradiation for a residual abdominal tumor, she has maintained complete remission for 2 years. Although RPLS is a rare complication of rituximab-CHOP chemotherapy, it should be considered in patients with DLBCL who present with acute neurological deterioration.