Vitamin D-dependent rickets Type II with alopecia: two case reports and review of the literature

Alopecia with Vitamin D-Dependent Rickets Type 2 A: A Case Report

Vitamin D-dependent rickets type II (VDDR2) is a rare inherited autosomal recessive disorder wherein the genetic mutation results in a defect in the vitamin D receptor (VDR), thus leading to target resistance to 1.25-dihydroxy vitamin D. This results in hypocalcemia, hypophosphatemia, secondary hyperparathyroidism, and rickets. We report a case of a four-year-old female child with diffuse alopecia starting 2 weeks after birth, along with frontal bossing, hypoplastic teeth, and an unusual presentation of multiple skin-colored papules over the back. Genetic testing confirmed vitamin D-dependent rickets type 2A.

Successful intermittent intravenous calcium treatment via the peripheral route in a patient with hereditary vitamin D-resistant rickets and alopecia

BACKGROUND

Hereditary vitamin D-resistant rickets (HVDRR) is a rare genetic disorder caused by mutations in the vitamin D receptor (VDR) gene, which result in end-organ resistance to 1,25-(OH)2D3. PATIENTs with HVDRR are mostly treated using i.v. calcium therapy with a central catheter. However, central catheter-related complications have been reported.

PATIENT

The patient was a 3-year-old boy presenting with waddling gait and alopecia. He had hypocalcemia [8 mg/dl (2 mmol/l)], hyperparathyroidism (1,232 ng/l), and elevated 1,25-(OH)2D3 levels (>250 pmol/l). DNA sequence analyses of the VDR gene showed a homozygous C-T transition at codon 152, resulting in a non-sense mutation in exon 5.

INTERVENTIONS AND OUTCOMES

The patient was initially treated with calcitriol (80 ng/kg/day) and high-dose oral calcium (150 mg/kg/day) for one year. At the end of the first year, intermittent (5 days per month) i.v. calcium therapy without a central catheter was initiated because of insufficient clinical and radiological improvement. After 2 years of intermittent i.v. calcium therapy, there was a clear improvement based on clinical progress and on X-ray and biochemical findings. No peripheral complications were reported either.

CONCLUSION

HVDRR with a non-sense mutation in the ligand-binding domain and alopecia was successfully treated with intermittent i.v. calcium without a central catheter.

[Long term follow up of a patient with type I vitamin D-dependent rickets]

BACKGROUND

Vitamin D dependent rickets type I is a rare hereditary disease due to a mutation in CYP27B1 encoding the 1α-hydroxylase gene. Clinically, the condition is characterized by hypocalcemic rickets in early infancy due to a deficit in the production of the vitamin D active metabolite 1,25-dihydroxy-vitamin D₃.

CASE REPORT

We report the case of a patient diagnosed at 11 months with follow-up until 9 years of age.

CONCLUSIONS

The pathophysiology of the disease and the relevance of early diagnosis and management are discussed.

Vitamin D metabolism, functions and needs: from science to health claims

BACKGROUND

Vitamin D is a nutrient long considered as essential for skeletal health but is now attracting interest from medical and nutritional communities as knowledge emerges of its biological function and its association with decreased risk of many chronic diseases.

RESULTS

A question emerges: How much more vitamin D do we need for these new functions of vitamin D? This review discusses vitamin D physiology and hypovitaminosis D and presents two vitamin D dietary policies: that according to regulatory authorities and that of nutrition scientists. Scientific evidence suggests that 25(OH)D serum levels should be over 75 nmol/L; otherwise, there is no beneficial effect of vitamin D on long-latency diseases. Current regulatory authority recommendations are insufficient to reach this level of adequacy. Observational and some prospective data show that vitamin D has a role in the prevention of cancer as well as immunity, diabetes and cardiovascular and muscle disorders, which supports the actions of 1α,25(OH)2D at cellular and molecular levels. The recent assessments done by the European Food Safety Authority should lead to new health claims.

CONCLUSIONS

Vitamin D, through food fortification and supplementation, is a promising new health strategy and thus provides opportunities for food industry and nutrition researchers to work together towards determining how to achieve this potential health benefit.

Alopecia in vitamin D-dependent rickets type II responding to 1α-hydroxycholecalciferol

A 4-year-old boy presented with rickets, alopecia and macrocephaly along with elevated serum levels of 1,25(OH)₂D₃ which was diagnostic of vitamin D-dependent rickets type II. The rickets responded to conventional doses of 1α-hydroxycholecalciferol together with oral calcium supplement and there was also improvement in the alopecia. In patients with vitamin D-dependent rickets type II with alopecia, although rickets improves with treatment, improvement in alopecia has not been reported before.

Marked disturbance of calcium homeostasis in mice with targeted disruption of the Trpv6 calcium channel gene

We report the phenotype of mice with targeted disruption of the Trpv6 (Trpv6 KO) epithelial calcium channel. The mice exhibit disordered Ca(2+) homeostasis, including defective intestinal Ca(2+) absorption, increased urinary Ca(2+) excretion, decreased BMD, deficient weight gain, and reduced fertility. Although our Trpv6 KO affects the closely adjacent EphB6 gene, the phenotype reported here is not related to EphB6 dysfunction.

INTRODUCTION

The mechanisms underlying intestinal Ca(2+) absorption are crucial for overall Ca(2+) homeostasis, because diet is the only source of all new Ca(2+) in the body. Trpv6 encodes a Ca(2+)-permeable cation channel responsible for vitamin D-dependent intestinal Ca(2+) absorption. Trpv6 is expressed in the intestine and also in the skin, placenta, kidney, and exocrine organs.

MATERIALS AND METHODS

To determine the in vivo function of TRPV6, we generated mice with targeted disruption of the Trpv6 (Trpv6 KO) gene.

RESULTS

Trpv6 KO mice are viable but exhibit disordered Ca(2+) homeostasis, including a 60% decrease in intestinal Ca(2+) absorption, deficient weight gain, decreased BMD, and reduced fertility. When kept on a regular (1% Ca(2+)) diet, Trpv6 KO mice have deficient intestinal Ca(2+) absorption, despite elevated levels of serum PTH (3.8-fold) and 1,25-dihydroxyvitamin D (2.4-fold). They also have decreased urinary osmolality and increased Ca(2+) excretion. Their serum Ca(2+) is normal, but when challenged with a low (0.25%) Ca(2+) diet, Trpv6 KO mice fail to further increase serum PTH and vitamin D, ultimately developing hypocalcemia. Trpv6 KO mice have normal urinary deoxypyridinoline excretion, although exhibiting a 9.3% reduction in femoral mineral density at 2 months of age, which is not restored by treatment for 1 month with a high (2%) Ca(2+) "rescue" diet. In addition to their deranged Ca(2+) homeostasis, the skin of Trpv6 KO mice has fewer and thinner layers of stratum corneum, decreased total Ca(2+) content, and loss of the normal Ca(2+) gradient. Twenty percent of all Trpv6 KO animals develop alopecia and dermatitis.

CONCLUSIONS

Trpv6 KO mice exhibit an array of abnormalities in multiple tissues/organs. At least some of these are caused by tissue-specific mechanisms. In addition, the kidneys and bones of Trpv6 KO mice do not respond to their elevated levels of PTH and 1,25-dihydroxyvitamin D. These data indicate that the TRPV6 channel plays an important role in Ca(2+) homeostasis and in other tissues not directly involved in this process.