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Background Lumasiran, a sub-cutaneous RNA-interference therapy, has been recently approved for primary hyperoxaluria type 1 (PH1), with doses and intervals according to body weight. Little is known as to its use in infants; the aim of this study was to describe treatment outcome in 3 infants who received lumasiran therapy before 2 years of age. Case-Diagnosis/Treatment Patient 1 was diagnosed antenatally and received lumasiran from day 9. According to the product information template (PIT), he received monthly lumasiran (3 times at 6 mg/kg, then 3 mg/kg), with hyperhydration and potassium citrate. Despite decreased plasma oxalate levels, persistent normal kidney function, and good tolerance, kidney ultrasound performed after 2 months found nephrocalcinosis, without normalization of urinary oxalate (UOx). The dose was increased back to 6 mg/kg, inducing a normalization in UOx. Nephrocalcinosis started to improve at month 10. Patient 2 was diagnosed at 2.5 months (acute kidney failure); nephrocalcinosis was present from diagnosis. She received monthly lumasiran (6 mg/kg), with progressive decrease in UOx and substantial improvement in kidney function but stable nephrocalcinosis after 9 injections. Patient 3 was diagnosed fortuitously (nephrocalcinosis) at 3.5 months and received lumasiran before genetic diagnosis, leading to decreased UOx and maintenance of normal kidney function. Nephrocalcinosis improved after 5 injections. Conclusions This report presents the youngest children treated with lumasiran worldwide. Lumasiran seems effective without side effects in infants but does not completely prevent the onset of nephrocalcinosis in the most severe forms. Higher doses than those proposed in the PIT might be required because of hepatic immaturity., Author(s): Marie-Noëlle Méaux [sup.1] [sup.2] [sup.3] , Anne-Laure Sellier-Leclerc [sup.1] , Cécile Acquaviva-Bourdain [sup.4] , Jérôme Harambat [sup.2] , Lise Allard [sup.2] , Justine Bacchetta [sup.1] [sup.3] [sup.5] Author Affiliations: [...]

Introduction: Vitamin D--dependent rickets type 1A (VDDR1A) is a rare genetic disease associated with loss-of-function variations in the gene encoding the vitamin D--activating enzyme 1α-hydroxylase (CYP27B1). Phenotype-genotype correlation is unclear. Long-term outcome data are lacking. The objective of this study was to describe characteristics and outcomes to search for a phenotype-genotype correlation. Methods: We retrospectively collected clinical data, genetic features, and outcomes from 24 genetically confirmed cases from 10 French centers; results are presented as median (min--max). Results: Clinical symptoms at diagnosis (age, 1.5 [0.5-8.7] years) were mainly bone and neurological abnormalities, and laboratory data showed hypocalcemia (1.97 [1.40-2.40] mmol/L), hypophosphatemia (-3.4 [-13.4 to (-)0.2] SD score for age), low 25OHD and low 1,25(OH)2D3, secondary hyperparathyroidism with PTH at 6.6 (1.3-13.7) times the upper limit for normal (ULN; PTH expressed as ULN to homogenize data presentation), and increased alkaline phosphatase (1968 [521-7000] IU/L). Bone radiographs were abnormal in 83% of patients. We identified 17 variations (11 missense, 3 frameshift, 2 truncating, and 1 acceptor splice site variations) in 19 families (homozygous state in 58% [11/19]). The partial loss-of-function variation p.(Ala129Thr) was associated with a milder phenotype: older age at diagnosis, higher serum calcium (2.26 vs 1.85 mmol/L), lower PTH (4.7 vs 7.5 ULN), and lower alkaline phosphatase (759 vs 2082 IU/L). Patients were treated with alfacalcidol. Clinical (skeletal, neurological), biochemical, and radiological outcomes were satisfactory, and complications occurred if there was bad adherence. Conclusion: Overall, our findings highlight good outcomes under substitutive treatment and the need of a closer follow-up of eyes, teeth, kidneys, and blood pressure in VDDR1A. [ABSTRACT FROM AUTHOR]

Cystinosis metabolic bone disease (CMBD) is an emerging concept in infantile nephropathic cystinosis, patients presenting with bone pains, fractures, and deformations during teenage or early adulthood. The underlying mechanisms remain unclear. Our aim was to explore the pro-inflammatory profile of osteoclastic lineage in cystinotic patients. We obtained blood samples from 14 cystinotic patients and 10 pediatric healthy controls. Peripheral blood mononuclear cells (PBMCs) were isolated and used to explore by RT-qPCR the transcript expression of 8 inflammatory markers (Il-6, Il-8, Il-1β, CXCL1, CCL2/MCP-1, CXCR3, Il-1 Receptor, Il-6 Receptor). In addition, when possible, PBMCs were differentiated into osteoclasts for further experiments. The expression of Il-6, IL-8, CXCR3, and CCL2/MCP-1 was significantly increased in PBMCs from cystinotic patients. We also explored the expression of Il-1 Receptor and Il-6 Receptor, two major pro-osteoclastic signal inducers, in osteoclasts differentiated from PBMCs from controls (N = 3) and patients (N = 4). The expression of IL-1 Receptor (but not IL-6 receptor) was increased in osteoclasts obtained from cystinotic patients., Conclusion: There is an inflammatory profile in PBMCs and osteoclastic lineage in cells obtained from cystinotic patients. CXCR3 and MCP-1 stimulate migration and activation of macrophages, that may explain the previously reported local increased osteoclastogenesis. The osteoclastic overexpression of IL-1 Receptor is a relevant observation in the field since blocking Il-1β signaling has recently been proposed as a novel therapeutic approach to improve muscular wasting in this orphan disease., What Is Known: • Cystinosis metabolic bone disease (CMBD), an emerging concept with unclear underlying mechanisms, induces bone pains, fractures and deformations in patients with cystinosis. • Blocking Il-1β signaling may be a novel therapeutic approach to improve muscular wasting in cystinosis., What Is New: • There is an inflammatory profile in PBMCs and osteoclastic lineage in cells obtained from cystinotic patients, with an over-expression of IL-1 Receptor in osteoclasts. • We provide another experimental rationale to propose targeted anti-inflammatory therapies in cystinotic patients with severe bone disease., Competing Interests: Declarations Competing interests The authors declare no competing interests., (© 2024. The Author(s).)