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BACKGROUND: Disease-related variants in PHEX cause XLH by an increase of fibroblast growth factor 23 (FGF23) circulating levels, resulting in hypophosphatemia and 1,25(OH)2 vitamin D deficiency. XLH manifests in early life with rickets and persists in adulthood with osseous and extraosseous manifestations. Conventional therapy (oral phosphate and calcitriol) improves some symptoms, but evidence show that it is not completely effective, and it can lead to nephrocalcinosis (NC) and hyperparathyroidism (HPT). Burosumab (anti-FGF23 antibody) has shown to be effective and safety in the clinical trials. METHODS: The current real-world collaborative study evaluated genetic, clinical and laboratory data of XLH Brazilian adult patients treated with burosumab. RESULTS: Nineteen unrelated patients were studied. Patients reported pain, limb deformities and claudication, before burosumab initiation. 78% of them were previously treated with conventional therapy. The severity of the disease was moderate to severe (15 patients with score >5). At the baseline, 3 patients presented NC (16.7%) and 12 HPT (63%). After 16 ± 8.4 months under burosumab, we observed a significant: increase in stature (p = 0.02), in serum phosphate from 1.90 ± 0.43 to 2.67 ± 0.52 mg/dL (p = 0.02); in TmP/GFR from 1.30 ± 0.46 to 2.27 ± 0.64 mg/dL (p = 0.0001), in 1,25 (OH)2 D from 50.5 ± 23.3 to 71.1 ± 19.1 pg/mL (p = 0.03), and a decrease in iPTH from 86.8 ± 37.4 pg/mL to 66.5 ± 31.1 (p = 0.002). Nineteen variants were found (10 novel). HPT tended to develop in patients with truncated PHEX variants (p = 0.06). CONCLUSIONS: This study confirms the efficacy and safety of burosumab on XLH adult patients observed in clinical trials. Additionally, we observed a decrease in iPTH levels in patients with moderate to severe HPT at the baseline.

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INTRODUCTION: X-linked hypophosphatemia is an orphan disease of genetic origin and multisystem involvement. It is characterized by a mutation of the PHEX gene which results in excess FGF23 production, with abnormal renal and intestinal phosphorus metabolism, hypophosphatemia and osteomalacia secondary to chronic renal excretion of phosphate. Clinical manifestations include hypophosphatemic rickets leading to growth abnormalities and osteomalacia, myopathy, bone pain and dental abscesses. The transition of these patients to adult life continues to pose challenges to health systems, medical practitioners, patients and families. For this reason, the aim of this consensus is to provide a set of recommendations to facilitate this process and ensure adequate management and follow-up, as well as the quality of life for patients with X-linked hypophosphatemia as they transition to adult life. MATERIALS AND METHODS: Eight Latin American experts on the subject participated in the consensus and two of them were appointed as coordinators. The consensus work was done in accordance with the nominal group technique in 6 phases: (1) question standardization, (2) definition of the maximum number of choices, (3) production of individual solutions or answers, (4) individual question review, (5) analysis and synthesis of the information and (6) synchronic meetings for clarification and voting. An agreement was determined to exist with 80% votes in favor in three voting cycles. RESULTS AND DISCUSSION: Transition to adult life in patients with hypophosphatemia is a complex process that requires a comprehensive approach, taking into consideration medical interventions and associated care, but also the psychosocial components of adult life and the participation of multiple stakeholders to ensure a successful process. The consensus proposes a total of 33 recommendations based on the evidence and the knowledge and experience of the experts. The goal of the recommendations is to optimize the management of these patients during their transition to adulthood, bearing in mind the need for multidisciplinary management, as well as the most relevant medical and psychosocial factors in the region.

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El raquitismo hipofosfatémico hereditario es una condición genética asociada con una mineralización ósea alterada causada por la deficiencia de fosfato. Produce deformidad esquelética y retraso del crecimiento en la infancia. Se describen diferentes patrones de herencia según el locus involucrado. Dado el solapamiento de los fenotipos y la dificultad en analizar genealogías reducidas, los estudios moleculares son importantes para establecer la causa genética y realizar el abordaje familiar. La forma recesiva del raquitismo hipofosfatémico (ARHR, OMIM #241520) es una condición extremadamente poco frecuente reportada en familias de origen europeo y de Oriente Medio. Las mutaciones con pérdida de función del gen DMP1 (dentin matrix acidic phosphoprotein 1) se asocian al raquitismo hipofosfatémico hereditario tipo 1. En este artículo presentamos el primer reporte de una familia argentina con raquitismo hipofosfatémico hereditario por mutación en DMP1

Hereditary hypophosphatemic rickets is a genetic condition associated with impaired bone mineralization caused by phosphate deficiency. It results in skeletal deformity and growth retardation in early childhood. Different inheritance patterns have been described according to the locus involved. Given the phenotypic overlapping and the difficulty in analyzing reduced genealogies, molecular studies are important to establish the genetic cause and implement a family-centered approach. The autosomal recessive form of hypophosphatemic rickets (ARHR, OMIM 241520) is an extremely rare condition reported in families of European and Middle Eastern descent. Loss-of-function mutations in the DMP1 (dentin matrix acidic phosphoprotein 1) gene are associated with hereditary hypophosphatemic rickets type 1. In this article, we describe the first report of an Argentine family with hereditary hypophosphatemic rickets due to a mutation in the DMP1 gene.

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Hereditary hypophosphatemic rickets is a genetic condition associated with impaired bone mineralization caused by phosphate deficiency. It results in skeletal deformity and growth retardation in early childhood. Different inheritance patterns have been described according to the locus involved. Given the phenotypic overlapping and the difficulty in analyzing reduced genealogies, molecular studies are important to establish the genetic cause and implement a family-centered approach. The autosomal recessive form of hypophosphatemic rickets (ARHR, OMIM 241520) is an extremely rare condition reported in families of European and Middle Eastern descent. Loss-of-function mutations in the DMP1 (dentin matrix acidic phosphoprotein 1) gene are associated with hereditary hypophosphatemic rickets type 1. In this article, we describe the first report of an Argentine family with hereditary hypophosphatemic rickets due to a mutation in the DMP1 gene.

El raquitismo hipofosfatémico hereditario es una condición genética asociada con una mineralización ósea alterada causada por la deficiencia de fosfato. Produce deformidad esquelética y retraso del crecimiento en la infancia. Se describen diferentes patrones de herencia según el locus involucrado. Dado el solapamiento de los fenotipos y la dificultad en analizar genealogías reducidas, los estudios moleculares son importantes para establecer la causa genética y realizar el abordaje familiar. La forma recesiva del raquitismo hipofosfatémico (ARHR, OMIM #241520) es una condición extremadamente poco frecuente reportada en familias de origen europeo y de Oriente Medio. Las mutaciones con pérdida de función del gen DMP1 (dentin matrix acidic phosphoprotein 1) se asocian al raquitismo hipofosfatémico hereditario tipo 1. En este artículo presentamos el primer reporte de una familia argentina con raquitismo hipofosfatémico hereditario por mutación en DMP1.

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BACKGROUND: X-linked hypophosphatemic rickets (XLHR) is a rare genetic disease, often delayed in diagnosis due to the low degree of suspicion and limited access to sophisticated diagnostic tools that confirm the diagnosis, such as genetic testing. METHODS: Through a cross-sectional and observational study, 26 patients with a previously presumptive diagnosis of X-linked hypophosphatemic rickets (based on clinical history, laboratory findings, and physical examination), were followed for approximately 12 months. During 12 months of follow-up, only 16 patients underwent genetic testing and enrolled in the study. Previous data were analyzed, such as clinical history (e.g., gender, current age, age of clinical diagnosis, age of admission to hospital, family history, and previous orthopedic surgery), physical exam, imaging tests (e.g., radiological changes) and laboratory tests (e.g., tubular maximum reabsorption rate of phosphate to glomerular filtration rate, alkaline phosphatase, and phosphate levels) at the time of the patient's admission to IEDE and UFRJ, to corroborate and substantiate our research. These data were extracted from the medical records of the patients. RESULTS: Among the 16 patients analyzed by molecular biology techniques, the new generation sequencing (NGS), using DNA samples from oral swabs, we obtained seven variants never previously described, which were verified by Sanger sequencing. Among the seven variants never previously described, the most common coding impact was the nonsense mutation. We found two frameshift, one intronic splicing variant, three nonsense, and one deletion splice junction loss. Among patients with new mutations who presented data in the medical record, 100% showed a reduction in TmP/GFR (average of 1.98 mg/dl), the most sensitive laboratory parameter at the time of diagnosis, as well as serum phosphorus (100% had hypophosphatemia on arrival at the referral hospitals--average of 2.4 mg/dl and median 2.3 mg/dl). We also performed NGS on three mothers of the patients with identified mutations. Among these mothers, only one tested negative for the mutation and no family history was reported as well. This mother had serum phosphate of 3.5 mg/dl (normal range: 2.5-4.5 mg/dl) at the time of genetic test collection. The others had a positive test, low serum phosphorus at the time of the molecular test, in addition to a positive family history. CONCLUSION: This study describes seven new variants in the PHEX gene and aims to increase the knowledge of the scientific community about the types of mutations involving this gene, increasing information on the genetic basis of this condition, enabling future considerations about genotype-phenotype correlation, in addition to diagnosis accurate and early.

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PURPOSE: Patients with hereditary hypophosphatemic rickets are short and disproportionate and very little information is available on segmental growth, but the body disproportion at adulthood leads us to think that the growth velocity of legs is slower. METHODS: A total of 96 children were included and molecular testing was carried out in 42. Children who reached adult height were classified into two groups according to their compliance to conventional treatment (phosphate supplement and calcitriol). Individual growth records of height and sitting height/height were plotted using Argentine reference data in 96 children and growth curves were estimated by fitting Preece-Baines Model 1 in 19 of the children. RESULTS: Molecular testing revealed sequence deleterious alterations or large deletions in 36/42 patients. During childhood, 76% of children grew below - 1.88 standard deviation score (SDS) and 97% had body disproportion. During adolescence, the mean peak height velocity for the good and poor compliance to treatment groups was 7.8 (0.6) and 5.4 (0.4) cm/year in boys and 7.0 (0.7) and 5.2 (0.8) cm/year in girls, respectively. At adulthood, the median sitting height/height ratio was 2.32 and 6.21 SDS for the good and poor compliance to treatment groups, respectively. The mean pubertal growth spurt of the trunk was -0.8 (1.4) SDS, with a short pubertal growth spurt of - 1.8 (0.4) SDS for limbs in the good compliance group. Median adult height in 13/29 males and 30/67 females was -4.56 and -3.16 SDS, respectively. CONCLUSION: For all patients the growth spurt was slower, secondary to a short growth spurt of limbs, reaching a short adult height with body disproportion that was more prominent in the poor compliance group.

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Abstract Background and objective: Magnesium ammonium phosphate stones (MAP), also known as struvite stones, are associated with urinary infection and impairment of renal unit. The aim of this study is to evaluate the urinary metabolic risk factors for recurrence of renal calculi in patients submitted to nephrectomy due to MAP stones. Methods: We retrospectively reviewed the charts of patients > 18 years old submitted to total nephrectomy due to pure MAP stones and pure calcium oxalate (CaOx) stones from July 2006 to July 2016. Urinary metabolic parameters were assessed through 24-hour urine exams ≥ 3 months after nephrectomy. Urinary metabolic parameters and new event related to lithiasis were compared. Results: Twenty-eight and 39 patients were included in MAP and CaOx group, respectively. Abnormalities in 24-hour urine samples were similar between groups. Hypercalciuria occurred in 7.1 and 10.3% of patients in MAP and CaOx group, respectively (p = 0.66), whereas hypocitraturia was present in 65.2 and 59.0% of patients with MAP and CaOx group, respectively (p = 0.41). No significant difference in new events was found between MAP and CaOx groups (17.9 vs. 23.1%, respectively; p = 0.60). Conclusion: A 24-hour urine evaluation should be offered to patients submitted to nephrectomy due to pure MAP stones in order to detect metabolic risk, improve treatment, and prevent stone recurrence.

Resumo Contexto e objetivo: Cálculos de fosfato de amônio e magnésio (FAM), também conhecidos como cálculos de estruvita, estão associados à infecção urinária e ao comprometimento da unidade renal. O objetivo deste estudo é avaliar os fatores de risco metabólico-urinários para recorrência de cálculos renais em pacientes submetidos à nefrectomia devido a cálculo de FAM. Métodos: Revisamos retrospectivamente os prontuários de pacientes > 18 anos submetidos à nefrectomia total devido a cálculos de FAM puro e cálculos de oxalato de cálcio puro (OxCa) de julho de 2006 a julho de 2016. Os parâmetros metabólicos urinários foram avaliados através de exames de urina de 24 horas ≥ 3 meses após a nefrectomia. Os parâmetros metabólicos urinários e um novo evento relacionado à litíase foram comparados. Resultados: Vinte e oito e 39 pacientes foram incluídos nos grupos FAM e OxCa, respectivamente. As anormalidades em amostras de urina de 24 horas foram similares entre os grupos. A hipercalciúria ocorreu em 7,1 e 10,3% dos pacientes nos grupos FAM e OxCa, respectivamente (p = 0,66), enquanto a hipocitratúria esteve presente em 65,2 e 59,0% dos pacientes nos grupos FAM e OxCa, respectivamente (p = 0,41). Nenhuma diferença significativa em novos eventos foi encontrada entre os grupos FAM e OxCa (17,9 vs. 23,1%, respectivamente; p = 0,60). Conclusão: Uma avaliação de urina de 24 horas deve ser oferecida aos pacientes submetidos à nefrectomia devido a cálculos de FAM puro, a fim de detectar risco metabólico, melhorar o tratamento e prevenir a recorrência de cálculos.

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Abstract Phosphopenic rickets may be caused by mutations in the PHEX gene (phosphate regulating endopeptidase homolog X-linked). Presently, more than 500 mutations in the PHEX gene have been found to cause hypophosphatemic rickets. The authors report a clinical case of a 4-year-old girl with unremarkable family history, who presented with failure to thrive and bowing of the legs. Laboratory tests showed hypophosphatemia, elevated alkaline phosphatase, normal calcium, mildly elevated PTH and normal levels of 25(OH)D and 1.25(OH)D. The radiological study showed bone deformities of the radius and femur. Clinical diagnosis of phosphopenic rickets was made and the genetic study detected a heterozygous likely pathogenic variant of the PHEX gene: c.767_768del (p.Thr256Serfs*7). This variant was not previously described in the literature or databases. Knowledge about new mutations can improve patient's outcome. Genetic analysis can help to establish a genotype-phenotype correlation.

Resumo O raquitismo fosfopênico pode ser causado por mutações no gene PHEX (ligado ao X do homólogo da endopeptidase que regula o fosfato). Atualmente, mais de 500 mutações no gene PHEX causam raquitismo hipofosfatêmico. Os autores relatam um caso clínico de uma menina de 4 anos com histórico familiar sem relevância, que apresentou falha no crescimento e arqueamento das pernas. Os exames laboratoriais mostraram hipofosfatemia, fosfatase alcalina elevada, cálcio normal, PTH levemente elevado e níveis normais de 25(OH)D e 1,25(OH)D. O estudo radiológico mostrou deformidades ósseas no rádio e no fêmur. O diagnóstico clínico do raquitismo fosfopênico foi realizado e o estudo genético detectou uma provável variante patogênica heterozigótica do gene PHEX: c.767_768del (p.Thr256Serfs*7). Esta variante não foi descrita anteriormente na literatura ou nas bases de dados. O conhecimento sobre novas mutações pode melhorar o desfecho de pacientes. A análise genética pode ajudar a estabelecer uma correlação genótipo-fenótipo.

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X-Linked Hypophosphatemia (XLH) is the most common cause of inherited hypophosphatemic rickets. Dental involvement, including spontaneous abscesses and/or fistulae, is an important part of the disease and has not been completely defined, especially in cohorts from developing countries. To describe oral health status in a cohort of Chilean patients with XLH and explore its correlation with biochemical presentation and treatment, we conducted a cross-sectional observational study of patients with PHEX mutation-confirmed XLH. All patients had an oral clinical exam, radiographic evaluation; clinical and biochemical data were obtained to determine their association with oral features. Twenty-six patients were included, 77% adults and 23% children. Most adults (89%) had past or current dental pulp pathology (abscesses and/or fistulae). Pulpal chamber enlargement and radiolucent apical lesions were common radiological features (94 and 74%, respectively). In children, abscess and/or fistulae were also common (33%). Caries index, which was determined by dmft/DMFT, was higher than the Chilean national average. Early and long-term therapy with phosphate and activated vitamin D was associated with lower carious index and attachment loss. XLH patients frequently present with high pulpal involvement and carious index. Conventional therapy was associated with lower carious index and attachment loss. These data highlight the importance of early and periodical dental care in order to prevent dental damage and assure a good quality of oral health for XLH patients.

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