No abstract

Next-generation sequencing has revolutionized the molecular diagnosis of individuals affected by genetic kidney diseases. Indeed, rapid genetic testing in individuals with suspected inherited nephropathy has not only important implications for diagnosis and prognosis but also for genetic counseling. Nephronophthisis (NPHP) and related syndromes, a leading cause of end-stage renal failure, are autosomal recessive disorders characterized by the variable presentation and considerable locus heterogeneity with more than 90 genes described as single-gene causes. In this case report, we demonstrate the utility of whole-genome sequencing (WGS) for the molecular diagnosis of NPHP by identifying two putative disease-causing intronic mutations in the NPHP3 gene, including one deep intronic variant. We further show that both intronic variants, by affecting splicing, result in a truncated nephrocystin-3 protein. This study provides a framework for applying WGS as a first-line diagnostic tool for highly heterogeneous disease such as NPHP and further suggests that deep intronic variations are an important underestimated cause of monogenic disorders.

A few cases of hypercalcemia related to Pneumocystis jirovecii pneumonia (PJP) have previously been described, supposedly associated with an 1α-hydroxylase enzyme-dependent mechanism. The prevalence and significance of hypercalcemia in PJP remain unclear, especially in kidney transplant recipients (KTR) who frequently display hypercalcemia via persisting hyperparathyroidism. We here retrospectively identified all microbiologically-proven PJP in adult KTR from 2005 to 2017 in the Lille University Hospital, and studied the mineral and bone metabolism parameters during the peri-infectious period. Clinical features of PJP-patients were analyzed according to their serum calcium level. Hypercalcemia (12.6 ± 1.6 mg/dl) was observed in 37% (18/49) of PJP-patients and regressed concomitantly to specific anti-infectious treatment in all cases. No other cause of hypercalcemia was identified. In hypercalcemic patients, serum levels of 1,25-dihydroxyvitamin D were high at the time of PJP-diagnosis and decreased after anti-infectious treatment (124 ± 62 versus 28 ± 23 pg/mL, p = 0.006 ) while PTH serum levels followed an inverse curve (35 ± 34 versus 137 ± 99 pg/mL, p = 0.009 ), suggesting together a granuloma-mediated mechanism. Febrile dyspnea was less frequent in hypercalcemic PJP-patients compared to non-hypercalcemic (29 versus 67%). In summary, hypercalcemia seems common during PJP in KTR. Unexplained hypercalcemia could thus lead to specific investigations in this particular population, even in the absence of infectious or respiratory symptoms.

Human herpesvirus (HHV)‐6A can be inherited and chromosomally integrated (iciHHV‐6A), and donor‐to‐recipient transmission has been reported in solid organ transplant. However, when HHV‐6A reactivation happens after transplant, the source of HHV‐6A is often not evident and its pathogenicity remains unclear. Here, we present an exhaustive case of donor‐to‐recipient transmission and reactivation of iciHHV‐6A through kidney transplant. The absence of HHV‐6A genome from the nails of the recipient excluded a recipient‐related iciHHV‐6A. Viral loads > 7 log10 copies/106 cells in donor blood samples and similarities of U38, U39, U69, and U100 viral genes between donor, recipient, and previously published iciHHV‐6A strains are proof of donor‐related transmission. Detection of noncoding HHV‐6 snc‐RNA14 using fluorescence in situ hybridization analysis and immunofluorescence staining of HHV‐6A gp82/gp105 late proteins on kidney biopsies showed evidence of reactivation in the transplanted kidney. Because HHV‐6A reactivation can be life threatening in immunocompromised patients, we provide several tools to help during the complete screening and diagnosis.

Rationale: Peptide receptor radionuclide therapy (PRRT) with radiolabeled somatostatin analogs is a targeted internal radiotherapy method used to treat tumors expressing somatostatin receptors. Concomitant amino acids perfusion is systematically performed in order to inhibit the proximal tubular uptake of the radionuclide and thus prevent nephrotoxicity.Patient concerns: a 67-year-old woman with an intestinal neuroendocrine tumor with multiple lymphadenopathies and liver metastases. The patient displayed a carcinoid syndrome with flushes including facial erythrosis and paresthesia. During the treatment, the patient exhibited emesis and severe cramps.Diagnosis: We describe incomplete proximal tubulopathy induced by an amino acid therapy with [177Lu]-DOTA0-Tyr3-octreotate, which was reversible after treatment discontinuation. This diagnosis relies on metabolic acidosis, hypophosphatemia due to renal loss, tubular proteinuria and generalized aminoaciduria. Serum creatinine remained stable during and after the procedure.Interventions: PRRT with radiolabeled somatostatin analog ([177Lu]-DOTA0-Tyr3-octreotate). In order to prevent PRRT induced nephrotoxicity, we used a solution of 20 amino acids including 22 g/L Lysine and 16.8 g/L Arginine. Metoclopramide was successfully used to control vomiting. During the treatment and at the time of cramps, the blood sample showed hypophosphatemia at 0.3 mmol/ L justifying intravenous phosphate supplementation. The cramps disappeared after this infusion.Outcomes: Hypophosphatemia with low TmPO4/GFR was observed as well as an increase in b2-microglobulinuria, urinary polyclonal light chains, and amino aciduria involving all amino acids. All these disturbances disappeared the day after the treatment and there was no acute kidney injury after 5 PRRT sessions. Six months after PRRT discontinuation, the patient had neither renal failure nor proximal tubulopathy. Aminoacid induced tubulopathy involves the main ligands of the megalin receptor. It has recently been demonstrated that cilastatin is a megalin inhibitor in the proximal tubule and therefore could represent an attractive alternative to amino acids for this purpose.Lessons: This case report is a description of a nephroprotective strategy in which partial, and transient tubulopathy is induced, in order to decrease proximal absorption of a tubulotoxic molecule. This little known strategy could be used to prevent proximal tubular injury caused by others megalin-mediated nephrotoxicity medication.Abbreviations: 177Lu = Lutetium 177, PRRT = peptide receptor radionuclide therapy, TmPO4/GFR = ratio of maximum rate of renal tubular reabsorption of phosphate to glomerular filtration rate, TRP = fractional tubular reabsorption of phosphate.