Nutritional rickets - Vitamin D and beyond

Recent Surge in Severe 25-hydroxyvitamin D Deficiency Among African American Children and Pregnant Women: Implications for Rickets

BACKGROUND

Nutritional rickets is disproportionately prevalent among African American children and is closely linked to vitamin D (VD) deficiency. This study aims to analyze the prevalence and trends of vitamin D deficiency in American children, as well as pregnant and lactating women, from 2001 to 2023, with a focus on African American children.

METHODS

We analyzed serum 25(OH)D levels from 2001 to 2023, as well as dietary and supplemental vitamin D intake from 2007 to 2020, among children aged 1-17 years and pregnant and lactating women. Data were from the US National Health and Nutrition Examination Survey.

RESULTS

In the 2021-2023 sample, African American children had the highest rate of severe 25(OH)D deficiency (< 25 nmol/L) at 13.8% among all racial groups. This represents a significant increase from 5% in 2001-2002. Additionally, 2% of African American toddlers aged 12-23 months had severely deficient 25(OH)D levels between 2003 and 2023. An increase in severe 25(OH)D deficiency was also observed in pregnant and lactating African American women during the 2021-2023 period. Furthermore, 83.3% of African American children and 61.4% of pregnant and lactating African American women had daily vitamin D intakes below 10 mcg (400 IU), the highest inadequacy rates among all racial groups from 2007 to 2020.

CONCLUSION

The recent rise in severe vitamin D deficiency among African American children, pregnant, and lactating women increases the risk of nutritional rickets and calls for prompt public health attention.

Vitamin D deficiency and associated demographic risk factors in children at a tertiary hospital in Abu Dhabi

BACKGROUND

Despite ample sunshine, vitamin D deficiency continues to be prevalent in the Middle East. This pilot study aimed to identify the rate of vitamin D deficiency at a tertiary hospital in Abu Dhabi and to identify the associated risk factors in children and adolescents.

METHODOLOGY

A retrospective observational study was conducted using electronic medical records of paediatric patients who underwent 25-hydroxyvitamin D testing at Sheikh Shakhbout Medical City, Abu Dhabi between 1 January 2020 and 31 December 2021. Data on age, gender, ethnicity, weight, body mass index and other potential risk factors for vitamin D deficiency in children were recorded. Patients who were already receiving treatment for vitamin D deficiency were excluded. The collected data were analysed using standard statistical methods.

RESULTS

Of 26,818 patients under 18 years of age who attended the outpatient clinic, 1519 underwent 25-hydroxyvitamin D testing; 51% were male (n = 755). After applying the exclusion criteria, 1311 participants were included, 755 (58%) of whom had vitamin D concentrations of ≤50 nmol/L. Vitamin D deficiency was more common in children aged ≥10 years (69%) than in those <10 years of age (53%) (p < 0.0001). The highest prevalence of vitamin D deficiency was in those older than 16 years (86%). More females (63%, n = 407) than males (52%, n = 348) were identified as vitamin D-deficient (p = 0.0001). Vitamin D deficiency was more commonly identified during summer and autumn (59%) than in winter and spring (44%, p < 0.00001).

CONCLUSION

Vitamin D deficiency is prevalent in children seeking medical care in the UAE, especially in girls, older children and adolescents, and during the summer and autumn. Paediatricians should have a low screening threshold for hypovitaminosis D, or widespread supplementation should be considered.

Vitamin D-Mediated Regulation of Intestinal Calcium Absorption

Vitamin D is a critical regulator of calcium and bone homeostasis. While vitamin D has multiple effects on bone and calcium metabolism, the regulation of intestinal calcium (Ca) absorption efficiency is a critical function for vitamin D. This is necessary for optimal bone mineralization during growth, the protection of bone in adults, and the prevention of osteoporosis. Intestinal Ca absorption is regulated by 1,25 dihydroxyvitamin D (1,25(OH)2 D), a hormone that activates gene transcription following binding to the intestinal vitamin D receptor (VDR). When dietary Ca intake is low, Ca absorption follows a vitamin-D-regulated, saturable pathway, but when dietary Ca intake is high, Ca absorption is predominately through a paracellular diffusion pathway. Deletion of genes that mediate vitamin D action (i.e., VDR) or production (CYP27B1) eliminates basal Ca absorption and prevents the adaptation of mice to low-Ca diets. Various physiologic or disease states modify vitamin-D-regulated intestinal absorption of Ca (enhanced during late pregnancy, reduced due to menopause and aging).

Nutritional rickets and vitamin D deficiency: consequences and strategies for treatment and prevention

INTRODUCTION

Rickets is typically characterized by bone deformities due to defective bone mineralization and chondrocyte maturation in growing bones. However, infantile rickets often goes unrecognized, because the skeletal abnormalities are more subtle and often can only be detected radiologically. Nutritional rickets is a major public health concern in several regions worldwide. It is most commonly caused by vitamin D and/or calcium deficiency.

AREA COVERED

We provide an overview of historical perspective, epidemiology, and pathophysiology of nutritional rickets. Additionally, we outline diagnostic approaches and highlight challenges in radiographic diagnosis of rickets. Finally, we present strategies for prevention and treatment of rickets.

EXPERT OPINION

Despite the evidence from clinical databases that rickets is a rare disease, it is likely that rickets is clinically underdiagnosed as studies designed to screen healthy children for radiographic evidence of rickets reported surprisingly much higher prevalence. It has been reported that some of the radiologic features of rickets can be misinterpreted as fractures. To prevent nutritional rickets, most if not all infants and young children, should receive vitamin D from formulas and foods that are fortified with vitamin D or supplementation to achieve a serum 25-hydroxyvitamin D of at least 20 ng/mL as recommended by the Institute of Medicine. It has been recommended by the Endocrine Society that to achieve maximum bone health for children and adults, a serum concentration of 25-hydroxyvitamin D should be at least 30 ng/mL and preferably 40-60 ng/mL. Pregnant women who are unable to obtain an adequate amount of vitamin D from sunlight exposure and natural and fortified diets should take a vitamin D supplement of 1500-2000 IUs daily as recommended by the Endocrine Society since it has been demonstrated that 600 IUs daily will not maintain a circulating 25-hydroxyvitamin D of at least 20 ng/mL and most pregnant women. If lactating women take approximately 6400 IUs of vitamin D daily, they provide enough vitamin D in their milk to satisfy their infant's requirement thereby preventing rickets.

Rickets guidance: part II-management

Here, we discuss the management of different forms of rickets, including new therapeutic approaches based on recent guidelines. Management includes close monitoring of growth, the degree of leg bowing, bone pain, serum phosphate, calcium, alkaline phosphatase as a surrogate marker of osteoblast activity and thus degree of rickets, parathyroid hormone, 25-hydroxyvitamin D₃, and calciuria. An adequate calcium intake and normal 25-hydroxyvitamin D₃ levels should be assured in all patients. Children with calcipenic rickets require the supplementation or pharmacological treatment with native or active vitamin D depending on the underlying pathophysiology. Treatment of phosphopenic rickets depends on the underlying pathophysiology. Fibroblast-growth factor 23 (FGF23)-associated hypophosphatemic rickets was historically treated with frequent doses of oral phosphate salts in combination with active vitamin D, whereas tumor-induced osteomalacia (TIO) should primarily undergo tumor resection, if possible. Burosumab, a fully humanized FGF23-antibody, was recently approved for treatment of X-linked hypophosphatemia (XLH) and TIO and shown to be superior for treatment of XLH compared to conventional treatment. Forms of hypophosphatemic rickets independent of FGF23 due to genetic defects of renal tubular phosphate reabsorption are treated with oral phosphate only, since they are associated with excessive 1,25-dihydroxyvitamin D production. Finally, forms of hypophosphatemic rickets caused by Fanconi syndrome, such as nephropathic cystinosis and Dent disease require disease-specific treatment in addition to phosphate supplements and active vitamin D. Adjustment of medication should be done with consideration of treatment-associated side effects, including diarrhea, gastrointestinal discomfort, hypercalciuria, secondary hyperparathyroidism, and development of nephrocalcinosis or nephrolithiasis.