Chronic hypophosphatemia caused by decreased intestinal absorption or increased renal clearance, may lead to rickets or osteomalacia independently of other predisposing abnormalities. The conditions commonly associated with increased renal clearance of phosphate are X-linked hypophosphatemic rickets, tumor associated rickets/osteomalacia, RTA and Fanconi syndrome. Recently we experienced 3 men with adult-onset, histologically proven osteomalacia associated with increased renal clearance of phosphate. None of them had a family history of bone disease, tumors or other tubular defects. All of these had remarkable biochemical and clinical improvement with medical treatment such as 1, 25-dihydroxyvitamin D and phosphate supplementation. Although we did not find tumors yet, we could not rule out the possibility of tumor-associated osteomalcia since it often takes several years to make a diagnosis because of small size, benign nature and unusual location of tumors. Thus, careful long-term follow up for tumor occurrence will be maintained in these patients with sporadic nonfamilial hypophosphatemic osteomalacia.
Bone Diseases ; Diagnosis ; Familial Hypophosphatemic Rickets ; Fanconi Syndrome ; Follow-Up Studies ; Humans ; Hypophosphatemia ; Intestinal Absorption ; Male ; Osteomalacia ; Rickets

OBJECTIVES: To study the value of serum fibroblast growth factor 23 (FGF23) in the diagnosis of hypophosphatemic rickets in children. METHODS: A total of 28 children who were diagnosed with hypophosphatemic rickets in Children's Hospital of Nanjing Medical University from January 2016 to June 2021 were included as the rickets group. Forty healthy children, matched for sex and age, who attended the Department of Child Healthcare of the hospital were included as the healthy control group. The serum level of FGF23 was compared between the two groups, and the correlations of the serum FGF23 level with clinical characteristics and laboratory test results were analyzed. The value of serum FGF23 in the diagnosis of hypophosphatemic rickets was assessed. RESULTS: The rickets group had a significantly higher serum level of FGF23 than the healthy control group (P<0.05). In the rickets group, the serum FGF23 level was positively correlated with the serum alkaline phosphatase level (r_s=0.38, P<0.05) and was negatively correlated with maximum renal tubular phosphorus uptake/glomerular filtration rate (r_s=-0.64, P<0.05), while it was not correlated with age, height Z-score, sex, and parathyroid hormone (P>0.05). Serum FGF23 had a sensitivity of 0.821, a specificity of 0.925, an optimal cut-off value of 55.77 pg/mL, and an area under the curve of 0.874 in the diagnosis of hypophosphatemic rickets (P<0.05). CONCLUSIONS Serum FGF23 is of valuable in the diagnosis of hypophosphatemic rickets in children, which providing a theoretical basis for early diagnosis of this disease in clinical practice.
Child ; Humans ; Fibroblast Growth Factor-23 ; Fibroblast Growth Factors ; Familial Hypophosphatemic Rickets/diagnosis* ; Rickets, Hypophosphatemic/diagnosis*

X-linked hypophosphatemic rickets is caused by loss-of-function mutations in PHEX, which encodes a phosphate-regulating endopeptidase homolog. We report a 26-year-old man with X-linked hypophosphatemic rickets who showed decreased serum phosphate accompanied by bilateral genu valgum and short stature. He had received medical treatment with vitamin D (alfacalcidol) and phosphate from the age of 3 to 20 years. He underwent surgery due to valgus deformity at the age of 14 and 15. Targeted gene panel sequencing for Mendelian genes identified a nonsense mutation in PHEX (c.589C>T; p.Gln197Ter) and a mosaic pattern where only 38% of sequence reads showed the variant allele. This mutation was not found in his mother, who had a normal phenotype. This is a case of a sporadic nonsense mutation in PHEX and up to date, this is the first case of a mosaic mutation in PHEX in Korea.
Adult ; Alleles ; Codon, Nonsense ; Congenital Abnormalities ; Familial Hypophosphatemic Rickets ; Genu Valgum ; Humans ; Korea ; Mothers ; Phenotype ; Rickets, Hypophosphatemic* ; Vitamin D

There is no report that describes in detail the radiological and intraoperative findings of rickets with symptomatic cervical ossification of the posterior longitudinal ligament. Here, we describe a case of X-linked hypophosphatemic rickets with cervical ossification of the posterior longitudinal ligament presenting unique radiological and intraoperative findings. The patient presented progressive tetraparesis. Magnetic resonance imaging studies revealed severe cervical spinal cord compression caused by ossification of the posterior longitudinal ligament. Computed tomography scans revealed homogeneously increased vertebral bone density. An expansive laminoplasty was performed. At surgery, homogeneously hard lamina bone was burdened in drilling and opening of the laminae. The patient's neurological symptoms were improved postoperatively. Bony fusion of the hinges occurred postoperatively. Therefore, expansive laminoplasty could be performed for symptomatic cervical ossification of the posterior longitudinal ligament with X-linked hypophosphatemic rickets. However, unusual bone characters should be taken into consideration for careful operation during surgery.
Bone Density* ; Familial Hypophosphatemic Rickets* ; Humans ; Longitudinal Ligaments ; Magnetic Resonance Imaging ; Ossification of Posterior Longitudinal Ligament* ; Rickets ; Spinal Cord Compression

The discovery and synthesis of vitamin D and the elucidation of the role of sunlight in the activation of the vitamin D precursors changed the syndromes of rickets from a therapeutic enigma to a socioeconomic and public health problem. Since Albright in 1937 first described vitamin D resistsnt rickets, which did not respond to treatment with the usual dose of vitamin D, it has progressively become a common form of rickets in practice. In addition, as the result of increasing understanding of renal physiology and careful investigation, a spectrum of renal tubular abnormalities have been identified which cause clinical rickets and which in many cases are insensitive to even large doses of vitamin D. We have reported a case of an unusual form of vitamin D resistant rickets which did not easily respond to treatment with high doses of vitamin D and was associated with hypocalcemia in multiple pathologic fractures in the lower extremities of the patient.
Familial Hypophosphatemic Rickets ; Fractures, Spontaneous ; Humans ; Hypocalcemia ; Lower Extremity ; Physiology ; Public Health ; Rickets ; Sunlight ; Vitamin D ; Vitamins

X-linked hypophosphatemia (XLH) is the most common form of familial hypophosphatemic rickets and it is caused by loss-of-function mutations in the PHEX gene. Recently, a wide variety of PHEX gene defects in XLH have been revealed; these include missense mutations, nonsense mutations, splice site mutations, insertions, and deletions. Recently, we encountered a 2-year-9-month-old female with sporadic hypophosphatemic rickets. She underwent osteotomy, dental abscess was evident, and there was severe bowing of the legs. A low serum phosphorus level in combination with elevated serum alkaline phosphatase activity and normal serum calcium is suggestive of hypophosphatemic rickets. PHEX gene analysis revealed a splice acceptor site mutation, c.934-1G>T (IVS8-1G>T), at the intron8 and exon9 junction. To the best of our knowledge, this mutation is novel and has not been reported. The results of this study expand and improve our understanding of the clinical and molecular characteristics and the global pool of patients with sporadic hypophosphatemic rickets.
Abscess ; Alkaline Phosphatase ; Calcium ; Codon, Nonsense ; Familial Hypophosphatemic Rickets ; Female ; Humans ; Leg ; Mutation, Missense ; Osteotomy ; Phosphorus ; Rickets, Hypophosphatemic* ; RNA Splice Sites

X-linked hypophosphatemia (XLH) represents the most common form of familial hypophosphatemia. Although significant advances have been made in the treatment of bone pathology, patients undergoing therapy continue to experience significantly decreased oral health-related quality of life. The following study addresses this persistent oral disease by further investigating the effect of DMP1 expression on the differentiation of XLH dental pulp cells. Dental pulp cells were isolated from the third molars of XLH and healthy controls and stable transduction of full-length human DMP1 were achieved. RNA sequencing was performed to evaluate the genetic changes following the induction of odontogenic differentiation. RNAseq data shows the upregulation of inhibitors of the canonical Wnt pathway in XLH cells, while constitutive expression of full-length DMP1 in XLH cells reversed this effect during odontogenic differentiation. These results imply that inhibition of the canonical Wnt pathway may contribute to the pathophysiology of XLH and suggest a new therapeutic strategy for the management of oral disease.
Humans ; Familial Hypophosphatemic Rickets ; Wnt Signaling Pathway ; Dental Pulp ; Quality of Life ; Cell Differentiation

X-linked hypophosphatemia (XLH) is a rare disease of elevated fibroblast growth factor 23 (FGF23) production that leads to hypophosphatemia and impaired mineralization of bone and teeth. The clinical manifestations of XLH include a high prevalence of dental abscesses and periodontal disease, likely driven by poorly formed structures of the dentoalveolar complex, including the alveolar bone, cementum, dentin, and periodontal ligament. Our previous studies have demonstrated that sclerostin antibody (Scl-Ab) treatment improves phosphate homeostasis, and increases long bone mass, strength, and mineralization in the Hyp mouse model of XLH. In the current study, we investigated whether Scl-Ab impacts the dentoalveolar structures of Hyp mice. Male and female wild-type and Hyp littermates were injected with 25 mg·kg^-1 of vehicle or Scl-Ab twice weekly beginning at 12 weeks of age and euthanized at 20 weeks of age. Scl-Ab increased alveolar bone mass in both male and female mice and alveolar tissue mineral density in the male mice. The positive effects of Scl-Ab were consistent with an increase in the fraction of active (nonphosphorylated) β-catenin, dentin matrix protein 1 (DMP1) and osteopontin stained alveolar osteocytes. Scl-Ab had no effect on the mass and mineralization of dentin, enamel, acellular or cellular cementum. There was a nonsignificant trend toward increased periodontal ligament (PDL) attachment fraction within the Hyp mice. Additional PDL fiber structural parameters were not affected by Scl-Ab. The current study demonstrates that Scl-Ab can improve alveolar bone in adult Hyp mice.
Mice ; Male ; Female ; Animals ; Familial Hypophosphatemic Rickets/metabolism* ; Bone and Bones/metabolism* ; Tooth/metabolism* ; Periodontal Ligament/metabolism*

BACKGROUNDHypophosphatemic rickets/osteomalacia is a group of diseases characterised by defective mineralization of bone due to hypophosphatemia and low 1,25-dihydroxy vitamin D. To explore the role of fibroblast growth factor 23 (FGF-23) in the regulation of phosphate homeostasis, we measured the circulating concentrations of this growth factor in healthy individuals and in patients with hypophosphatemic rickets/osteomalacia.

METHODSNineteen patients with hypophosphatemic rickets/osteomalacia were included in hypophosphatemic group (HP, 12 female and 7 male, mean age was 30 years), and 19 healthy age-matched individuals served as the control group. Full length FGF-23 fragments were measured by two-site enzyme-linked immunosorbent assay.

RESULTSMean FGF-23 concentrations were significantly higher in the HP group ((87.4 +/- 43.6) pg/ml) compared with the control group ((19.2 +/- 6.16) pg/ml; P < 0.001). In 1 patient with tumour-induced osteomalacia, serum FGF-23 concentrations were 84.1 pg/ml; these concentrations were normalized 2 hours after a hemangiopericytoma resection (7.8 pg/ml). Subsequently, serum 1,25(OH)(2) vitamin D3 concentrations significantly increased from 21.3 pg/ml to 89.3 pg/ml, and serum phosphorus levels were normalized.

CONCLUSIONSSerum FGF-23 concentrations were markedly elevated in patients with hypophosphatemic rickets. FGF-23 plays an important role in the pathogenesis of hypophosphatemic rickets/osteomalacia.

Adolescent ; Adult ; Calcitriol ; blood ; Child ; Child, Preschool ; Enzyme-Linked Immunosorbent Assay ; Familial Hypophosphatemic Rickets ; blood ; Female ; Fibroblast Growth Factors ; blood ; Humans ; Male ; Middle Aged ; Osteomalacia ; blood ; Phosphates ; blood ; Young Adult

Rickets is a syndrome, characterised pathophysiologically by a failure of normal mineralization of bone and epiphyseal cartilage and clinically by skeletal deformity in growing children. The four principal causes of rickets are; vitamin D deficency, renal tubular insufficiency, chronic renal insufficiency, and hypophosphatasia. Of these, vitamin D resistant rickets may result from primary defect in function of the renal tubular reabsorption for phosphorus, later accompsnied with secondary hyperparathyroidism. We experiened a rare case of hypophosphstemic vitamin D resistant rickets accompanied with secondary hyperparathyroidism in adolescence.
Adolescent ; Child ; Congenital Abnormalities ; Familial Hypophosphatemic Rickets ; Growth Plate ; Humans ; Hyperparathyroidism, Secondary ; Hypophosphatasia ; Miners ; Phosphorus ; Renal Insufficiency, Chronic ; Rickets ; Vitamin D ; Vitamins