Vitamin D-dependent rickets (VDDR) type 1: case series of two siblings with a CYP27B1 mutation and review of the literature / Raquitismo dependente de vitamina D: tipo 1: série de casos de dois irmãos com mutação CYP27B1 e revisão da literatura

Abstract Two siblings presented with clinical and biochemical features of rickets, initially suspected as hypophosphatemic rickets. There was no improvement initially, hence the siblings were reinvestigated and later diagnosed as having vitamin D-dependent rickets (VDDR) type 1 due to a rare mutation in the CYP27B1 gene encoding the 1α-hydroxylase enzyme. Both siblings improved with calcitriol supplementation. The initial presentation of VDDR is often confusing and algorithmic evaluation helps in diagnosis. We also present a brief review of the literature, including genetics.

Resumo Dois irmãos apresentaram características clínicas e bioquímicas do raquitismo, com suspeita clínica inicial de raquitismo hipofosfatêmico. Não houve melhora no início, portanto os irmãos foram reavaliados e, posteriormente, diagnosticados com raquitismo dependente de vitamina D (VDDR) tipo 1 devido a uma rara mutação no gene CYP27B1, que codifica a enzima 1a-hidroxilase. Ambos os irmãos melhoraram com a suplementação de calcitriol. A apresentação inicial do VDDR geralmente é confusa e a avaliação algorítmica ajuda no diagnóstico. Também apresentamos uma breve revisão da literatura, incluindo genética.

A case of vitamin D hydroxylation-deficient rickets type 1A caused by 2 novel pathogenic variants in CYP27B1 gene

Vitamin D hydroxylation-deficient rickets type 1A (VDDR1A, OMIM 264700) is a rare autosomal recessive inherited disorder. Pathogenic variants in the CYP27B1 gene lead to loss of 1α-hydroxylase activity. We report the case of a 22-month-old toddler who presented with growth retardation and delayed development. The patient exhibited the typical laboratory findings of VDDR1A, including hypocalcemia (calcium: 5.2 mg/dL), elevated serum level of alkaline phosphatase (2,600 U/L), elevated serum level of intact-parathyroid hormone (238 pg/mL), low 1,25(OH)₂D₃ level (11.2 pg/mL), and normal 25(OH)D₃ level (40.7 ng/mL). His height and weight were 76.5 cm and 9.5 kg, respectively (both <3rd percentile). The Bayley Scales of Infant and Toddler Development II indicated significantly delayed development (mental development index <50, psychomotor development index <50). The patient was a compound heterozygous for two novel pathogenic variants in the CYP27B1 gene: c.57_69del (p.Glu20Profs*2) and c.171dupG (p.Leu58Alafs*275), inherited from his mother and father, respectively. The patient showed remarkable improvement after treatment with calcitriol and calcium carbonate.

Vitamin D Dependent Rickets Type 1A Caused by CYP27B1 Mutation

Vitamin D dependent rickets type 1A (VDDR1A) is an autosomal recessive disorder caused by mutations in CYP27B1 . Clinical findings are growth retardation, hypotonia, muscle weakness, hypocalcemic seizures, and radiological features of rickets. We aimed to present the VDDR1A case with a genetic study of CYP27B1 . The 14-month-old boy was admitted to the hospital due to a seizure. Serum calcium, phosphorus, alkaline phosphatase, parathyroid hormone (PTH), 25(OH) vitamin D, and 1,25(OH)2 vitamin D values were 5.1 mg/dL, 3.7 mg/dL, 705 IU/L, 429 pg/mL, 24.9 ng/mL, and 8.8 pg/mL, respectively. Radiological study showed cupping and fraying of the distal ulna and radius. The molecular genetic study revealed that the patient had a compound heterozygous mutation, Phe443Profs*24 and c.589+1G>A, in CYP27B1 . Genetic analysis of the family members presented that the mother was heterozygous for the mutation c.589+1G>A, and that the father was heterozygous for Phe443Profs*24. The patient was treated with calcium lactate and calcitriol. Until now, six Korean patients with VDDR1A have been studied. Including this case, Korean patients with VDDR1A were found to have only three different mutations in 14 alleles, indicating that the mutation in the CYP27B1 gene is homogeneous in the Korean population.

Normal physiological functions in two animal species with highly different vitamin d status compared to that of humans / Funciones fisiológicas normales en dos especies animales con estatus de vitamina d muy diferentes del actual en seres humanos

Mole rats live in permanent darkness, in networks of underground tunnels (which extend up to 1 km in the subsoil), excavated with their incisors, in warm and semi-arid areas of South Africa. Mole rats have an unusually impoverished vitamin D3 status with undetectable and low plasma concentrations of 25- hydroxyvitamin D3 and 1α,25-dihydroxyvitamin D3, respectively. They express 25-hydroxylase in the liver and 1-hydroxylase and 24-hydroxylase in their kidneys. The presence of specific receptors (VDR) was confirmed in the intestine, kidney, Harderʼs glands and skin. In spite of their poor vitamin D3 status, the apparent fractional intestinal absorption of calcium, magnesium and phosphate was high, always greater than 90%. Oral supplementation with cholecalciferol to mole rats did not improve the efficiency of gastrointestinal absorption of these minerals. Mole ratsdo not display the typical lesion of rickets: hypertrophic and radiolucent growth cartilages. Histological studies reported normal parameters of trabecular and cortical bone quality. Marmosets (monkeys of the New World) are not hypercalcaemic, eventhough they exhibit much higher levels of 25-hydroxyvitamin D3, 1α,25-dihydroxyvitamin D3 and parathyroid hormonethan that of rhesus monkeys and humans. Fed a high vitamin D3 intake (110 IU/day/100 g of body weight), a fraction of the experimental group was found to display osteomalacic changes in their bones: distinct increases in osteoid surface, relative osteoid volume, and active osteoclastic bone resorption. These findings suggest that some marmosets appears to suffer vitamin D-dependent rickets, type II. The maximum binding capacity of the VDR or the dissociation constant of VDR1α,25(OH)2D3 complex of mole rats and New World monkeys are distinctly different of VDR isolated from human cells. Health status of those species appears to be adaptations to the mutations of their VDR. Though rare, as mutations may occur at any time in any patient, the overall message of this review to clinicians may be: recent clinical studies strongly suggests that the normality of physiological functions might be a better indicator of the health status than the serum levels of vitamin D metabolites. (AU)

Las ratas topo viven en la oscuridad permanente, en redes de túneles subterráneos excavadas con sus incisivos (que se extienden hasta 1 km en el subsuelo), en áreas cálidas y semiáridas de Sudáfrica. Las ratas topo tienen un estatus de vitamina D3 inusualmente empobrecido con concentraciones plasmáticas indetectables de 25-hidroxivitamina D3 y bajas de 1α, 25-dihidroxivitamina D3. Poseen 25-hidroxilasa en el hígado y 1-hidroxilasa y 24-hidroxilasa en sus riñones. La presencia de receptores específicos (VDR) ha sido confirmada en el intestino, el riñón, las glándulas de Harder y la piel. A pesar de su pobre estatus de vitamina D3,la absorción fraccional intestinal aparente de calcio, magnesio y fosfato fue alta, siempre superior al 90%. La suplementación oral con colecalciferol a las ratas topo no mejoró la eficacia de la absorción gastrointestinal de estos minerales. No muestran la lesión típica del raquitismo: cartílagos de crecimiento hipertróficos y radiolúcidos. Varios estudios histológicos confirman los hallazgos radiológicos y se informan parámetros normales de la calidad ósea trabecular y cortical. Los titíes (monos del Nuevo Mundo) exhiben calcemias normales con niveles más elevados de 25-hidroxivitamina D3, 1α,25-dihidroxivitamina D3 y hormona paratiroidea que los monos rhesus y los seres humanos. Un tercio de un grupo de titíes alimentados con una alta ingesta de vitamina D3 (110 I/día/100 g de peso corporal) exhibió cambios osteomalácicos en sus huesos: aumento en la superficie osteoide, volumen osteoide y activa reabsorción osteoclástica. Estos hallazgos sugieren que una fracción de la población de titíes padece raquitismo dependiente de vitamina D, tipo II. Debido a mutaciones ocurridas hace millones de años, las máximas capacidades de ligamiento del VDR o los valores de la constante de disociación del complejo VDR-1α,25(OH)2D3 de las ratas topo o monos del Nuevo Mundo son muy diferentes de los verificables en receptores aislados de células humanas actuales. El mensaje de esta revisión a los médicos clínicos podría ser: varios estudios clínicos recientes indican que la normalidad de las funciones fisiológicas de un paciente es un mejor indicador de su salud que los niveles séricos de los metabolitos de la vitamina D. (AU)

Women with recurrent spontaneous abortion have decreased 25(OH) vitamin D and VDR at the fetal-maternal interface

Immunological mechanisms have been proposed to underlie the pathogenesis of recurrent spontaneous abortion (RSA). Vitamin D has a potent immunomodulatory effect, which may affect pregnancy outcome. The objective of this study was to investigate 25-hydroxyvitamin D [25(OH) D] concentration and vitamin D receptor (VDR) expression in the decidual tissues of RSA patients. Thirty women with RSA (RSA group) and thirty women undergoing elective abortion (control group) were recruited during 2016 from gynecology outpatient clinics. We measured 25(OH) D, interleukin (IL)-17, IL-23, transforming growth factor β (TGF-β), VDR and 1-α-hydroxylase (CYP27B1) in decidual tissues collected during the abortion procedure. In the RSA group, 25(OH) D and TGF-β were significantly decreased while IL-17 and IL-23 were significantly increased compared with the control group. VDR expression was significantly decreased in the RSA group compared with the control group. Logistic regression analysis showed a significant negative correlation between 25(OH) D in decidual tissues and RSA. These results indicated that vitamin D concentrations in the decidua are associated with inflammatory cytokine production, suggesting that vitamin D and VDR may play a role in the etiology of RSA.

Long-term clinical outcome and the identification of homozygous CYP27B1 gene mutations in a patient with vitamin D hydroxylation-deficient rickets type 1A

Vitamin D hydroxylation-deficient rickets type 1A (VDDR1A) is an autosomal recessively-inherited disorder caused by mutations in CYP27B1 encoding the 1α-hydroxylase enzyme. We report on a female patient with VDDR1A who presented with hypocalcemic seizure at the age of 13 months. The typical clinical and biochemical features of VDDR1A were found, such as hypocalcemia, increased alkaline phosphatase, secondary hyperparathyroidism and normal 25-hydroxyvitamin D3 (25(OH)D₃). Radiographic images of the wrist showed metaphyseal widening with cupping and fraying of the ulna and distal radius, suggesting rickets. A mutation analysis of the CYP27B1 gene identified a homozygous mutation of c.589+1G>A in the splice donor site in intron 3, which was known to be pathogenic. Since that time, the patient has been under calcitriol and calcium treatment, with normal growth and development. During the follow-up period, she did not develop genu valgum, scoliosis, or nephrocalcinosis.

Relevance of CYP27B1 gene promoter polymorphism to autoimmune thyroid diseases / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the relationship between CYP27B1 gene promoter polymorphism and autoimmune thyroid diseases.</p><p><b>METHODS</b>A case-control study including 158 patients with Graves' disease (GD), 174 patients with Hashimoto's thyroiditis (HT) and 172 matched controls was conducted. Three genotypes of CYP27 B1 gene -1260 site (CC, AA and AC) were determined by restriction fragment length polymorphism (PCR-RFLP) assay and confirmed by sequencing.</p><p><b>RESULTS</b>The genotypic distribution of CYP27 B1 gene-1260 site showed no deviation from Hardy-Weinberg equilibrium. The genotype and allele frequencies of -1260A/C were CC34.3%, AA19.2%, AC46.5%, C57.6%, and A42.4% in the control group, 48.1%, 13.3%, 38.6%, 67.4%, and 32.6% in GD group, and 47.1%, 10.3%, 42.5%, 68.4%, and 31.6% in HT group, respectively. Significant difference was found in the genotype and allele frequencies in -1260A/C polymorphism between GD and the control groups (Chi2=6.80, P<0.05 for genotype frequencies, and Chi2=6.79, P<0.05 for allele frequencies) and between HT and the control groups (Chi2=8.39, P<0.05 for genotype frequencies, and Chi2=8.71, P<0.05 for allele frequencies).</p><p><b>CONCLUSION</b>CYP27 B1 promoter -1260 polymorphism is associated with GD or HT in Chinese Han population.</p>

The effects of serum calcium and 1 alpha hydroxylase on the expression of 24-hydroxylase gene / 中国应用生理学杂志

<p><b>AIM</b>To investigate the effects of 1 alpha hydroxylase and serum calcium on the expression of 24-hydroxylase gene in mice kidney.</p><p><b>METHODS</b>Mice with targeted deletion of the 25-hydroxyvitamin D 1 alpha hydroxylase gene(1alpha (OH)ase-/-), and the vitamin D receptor gene (VDR-/-) were used. The study of each mutant had two groups which were (1) mutant with high calcium diet, which maintained fertility but left mice hypocalcaemia; (2) mutant with high lactose diet, which normalized calcium in two mutant. Mice in same litter were as control. There were six groups in total and each group had five mice. All mice were killed at 10-week-old. Serum calcium was determined by an autoanalyzer. RNA was isolated from mouse kidney and the express of 1 alpha hydroxylase gene and 24-Hydroxylase gene were studied by RT-PCR.</p><p><b>RESULTS</b>On the high calcium intake, all mutant animals were hypocalcaemia (1alpha (OH)ase-/- (78 +/- 10.4) mg/L, P < 0.05; VDR-/- (68 +/- 9.8) mg/L, P < 0.05. WT (111 +/- 16.5 mg/L), but when the high lactose diet was administered, serum calcium levels in two mutant mice rose to wild-type levels. The 1 alpha hydroxylase gene was expressed at very higher levels in the vitamin D receptor mutant mice than in wild-type mice when animals received a high calcium intake; This was reduced by eliminating hypocalcaemia with the high lactose diet. Expression of the 24(OH)ase gene was extremely down-regulated in two mutant mice on the high calcium diet but was restored to wild-type levels on the high lactose diet.</p><p><b>CONCLUSION</b>The express of 24-hydroxylase gene was directly regulated by serum calcium rather than 1 alpha-hydroxylase. These studies indicate that both the serum calcium and 1 alpha-hydroxylase exert effects on the expression of 24-hydroxylase gene, but 1 alpha-hydroxylase take the effects by elevated the concentration of serum calcium. There are no direct interaction between 1 alpha-hydroxylase gene and 24-hydroxylase gene.</p>

T-cell function in long term haemodialysis patients: impact of secondary hyperparathyroidism, oral one alpha calcidol and dialysis duration

The aim of this work was to study T-lymphocyte function in relation to secondary hyperparathyroidism, oral one alpha-calcidol treatment and dialysis duration. Eighty chronic renal failure patients who were maintained on regular haemodialysis treatment for 6-144 months [CRF] and 20 normal control subjects [N] were studied. Cases known to have autoimmune diseases, other diseases, which would affect the immune system or receiving medications known to affect immunity were excluded. CRF cases were 45 males and 35 females and their age was 43.06 +/- 11.1 years, while N cases were 12 males and 8 females and their age was 35.6 +/- 9.79 years. A11 CRF cases were receiving 1-alpha-calcidol orally as 1 mug/day for at least 3 months before the study onset. CRF and N cases were clinically examined and were tested for serum urea and creatinine, serum calcium and phosphorus, serum level of intact parathormone [RIA] beside the in vitro assessment of lymphoblastoid transformation of peripheral blood lymphocytes with and without phytohaemagglutinin [PHA] stimulation. The serum level of intact parathormone varied significantly among CRF cases; it was < 40 pg/ml in 13 [CRF1], 40-80 in 14 [CRF2] and > 80 in 53 [CRF3]. Among these 3 subgroups, pre-activation of T-lymphocytes was significantly higher in CRF3 [28 +/- 3.94 vs. 33.7 +/- 5.44 vs. 37.36 +/- 3.58% in CRF1, 2, 3 respectively],while PHA induced T-cell proliferation was significantly higher in CRF1 [77.54 +/- 3.97 vs. 73.7 +/- 4.83 vs. 59.9 +/- 7.37% in CRF1, 2, 3, respectively]. Duration of dialysis [DX] was significantly shorter in CRF1 [15.6 +/- 5.94 vs. 33.57 +/- 11.9 vs. 79.7 +/- 30.2 months in CRF1, 2, 3, respectively]. There was no significant difference between the 3 subgroups in dose or duration of 1-alpha-calcidol treatment. CRF1 had significantly higher s-phosphorus and s-PTH, significantly lower PHA induced T-cell proliferation and insignificant difference in serum calcium and T-lymphocytes pre-activation when compared to N [5.32 +/- 0.41 vs. 3.39 +/- 0.64 mg%, 30.08 +/- 4.89 vs. 19 +/- 4.57 pg/ml, 77.54 +/- 3.97 vs. 84.8 +/- 2.8%, 9.73 +/- 1.07 vs. 9.92 +/- 0.48 mg% and 28 +/- 3.94 vs. 29.2 +/- 4.73%,respectively]. DX had a significantly +ve correlation with either PTH level or T-lymphocytes pre-activation and a significantly -ve correlation with PHA induced T-cell proliferation. PTH had a significantly +ve correlation with T-lymphocytes pre-activation and a significantly -ve correlation with PHA induced T-cell proliferation. The study concluded that increased DX duration is responsible for: Significant increase in s-PTH; increased resistance of parathyroid to suppression by 1-alpha-calcidol and progressive deterioration of T-cell function as proved by increased T-lymphocytes pre-activation and decreased PHA induced T-cell proliferation

La vitamina D: implicaciones en la salud y el embaraza / Vitamin D: implications in health and pregnancy

La vitamina D cobró importancia desde que se descubrió la naturaleza esteroidea y carácter hormonal de uno de sus metabolitos: el calcitriol. Su participación en el mantenimiento de la homeostasis mineral, así como su capacidad para regular la transcripción génica y fomentar la diferenciación celular, han hecho de su estudio tema de gran interés. Los recientes avances en el estudio de la enzima encargada de convertir la 25-hidroxivitamina D en 1.25-dihidroxivitamina D3 (calcitriol), así como la descripción de su mecanismo de acción, han permitido ampliar el conocimiento de los factores reguladores que controlan el equilibrio del sistema endocrino de la vitamina D, y de las implicaciones del calcitriol en la salud en general y en el embarazo en particular.