SENIOR-LØKEN SYNDROME: A Case Series and Review of the Renoretinal Phenotype and Advances of Molecular Diagnosis

PURPOSE: To report genetic and clinical findings in a case series of 10 patients from eight unrelated families diagnosed with Senior-Løken syndrome. METHODS: A retrospective study of patients with Senior-Løken syndrome. Data collected included clinical findings electroretinography and ocular imaging. Genetic analysis was based on molecular inversion probes, whole-exome sequencing (WES), and Sanger sequencing. RESULTS: All patients who underwent electrophysiology (8/10) had widespread photoreceptor degeneration. Genetic analysis revealed two mutations in NPHP1, two mutations in NPHP4, and two mutations in IQCB1 (NPHP5). Five of the six mutations identified in the current study were found in a single family each in our cohort. The IQCB1-p.R461* mutation has been identified in 3 families. Patients harboring mutations in IQCB1 were diagnosed with Leber congenital amaurosis, while patients with NPHP4 and NPHP1 mutations showed early and sector retinitis pigmentosa, respectively. Full-field electroretinography was extinct for 6 of 10 patients, moderately decreased for two, and unavailable for another 2 subjects. Renal involvement was evident in 7/10 patients at the time of diagnosis. Kidney function was normal (based on serum creatinine) in patients younger than 10 years. Mutations in IQCB1 were associated with high hypermetropia, whereas mutations in NPHP4 were associated with high myopia. CONCLUSION: Patients presenting with infantile inherited retinal degeneration are not universally screened for renal dysfunction. Modern genetic tests can provide molecular diagnosis at an early age and therefore facilitate early diagnosis of renal disease with recommended periodic screening beyond childhood and family planning

PTH Regulation by the Klotho/FGF23 Axis in CKD

Secondary hyperparathyroidism (SHPT) is an important complication of chronic kidney disease (CKD) and end-stage renal disease (ESRD), particularly among patients receiving dialysis. Downregulation of the parathyroid hormone (PTH), vitamin D (VDR), and calcium-sensing receptors (CaR) represent critical steps that lead to abnormalities in mineral metabolism, including high phosphate, low calcium, and vitamin D deficiency. Circulating fibroblast growth factor 23 (FGF23) concentration increases in CKD and the complex klotho-FGF receptor decreases in hyperplastic parathyroid glands of uremic patients, contributing to SHPT. In this chapter, we describe the parathyroid glands physiology and its normal and pathological regulation by the FGF23/Klotho axis in CKD