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

Clinical characteristics and long-term management for patients with vitamin D-dependent rickets type II: a retrospective study at a single center in Saudi Arabia

Introduction

Hereditary Vitamin D-dependent rickets type II (HVDDR-type II) is a rare autosomal recessive disorder caused by molecular variation in the gene encoding the vitamin D receptor (VDR). This study aims to evaluate phenotype and genotype characteristics and long-term follow-up of the largest group of patients with (HVDDR-type II) in Saudi Arabia.

Methodology

We conducted a retrospective chart review to collect the clinical, biochemical, and genetic data for all HVDDR-type II patients currently receiving treatment at King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia.

Results

A total of 42 patients, 57.1% female, and 42.9% male were included in the study. Seven patients were treated with high doses of oral calcium, while 35 patients were treated with IV calcium infusion. The median age at presentation was 15.5 months. Alopecia was found in 97.6%, 21.4% presented with bowing legs, 14.3% with delayed walking, 9.5% with seizure, and 2.4% presented with respiratory failure, while a family history of the disease was positive in 71.4% of total patients. Molecular genetic testing of the VDR gene in our cohort identified six different gene variants c.885 C>A (p.Tyr295Ter), c.88 C>T (p.Arg30Ter), c.1036G>A (p.Val346Met), c.820C>T (p.Arg274Cys), c.803 T>C (p.Ile268Thr), and c.2T>G (p.Met1?).

Conclusion

We are describing the largest cohort of patients with HVDDR-type II, their clinical biochemical findings, and the most prevalent genetic variants in our population.

Hereditary Rickets: A Quick Guide for the Pediatrician

With the increased discovery of genes implicated in vitamin D metabolism and the regulation of calcium and phosphate homeostasis, a growing number of genetic forms of rickets are now recognized. These are categorized into calciopenic and phosphopenic rickets. Calciopenic forms of hereditary rickets are caused by genetic mutations that alter the enzymatic activity in the vitamin D activation pathway or impair the vitamin D receptor action. Hereditary forms of phosphopenic rickets, on the other hand, are caused by genetic mutations that lead to increased expression of FGF23 hormone or that impair the absorptive capacity of phosphate at the proximal renal tubule. Due to the clinical overlap between acquired and genetic forms of rickets, identifying children with hereditary rickets can be challenging. A clear understanding of the molecular basis of hereditary forms of rickets and their associated biochemical patterns allow the health care provider to assign the correct diagnosis, avoid non-effective interventions and shorten the duration of the diagnostic journey in these children. In this mini-review, known forms of hereditary rickets listed on the Online Mendelian Inheritance in Man database are discussed. Further, a clinical approach to identify and diagnose children with hereditary forms of rickets is suggested.

Rickets in association with skin diseases and conditions: A review with emphasis on screening and prevention

BACKGROUND

Rickets is a common disease worldwide. In the developed world, its prevalence dramatically decreased but still diagnosed in at-risk populations. The skin plays a critical role in vitamin D synthesis. Therefore, several skin diseases, especially keratinization disorders, could lead to impaired vitamin D metabolism and vitamin D deficient rickets.

OBJECTIVE

The article aimed to summarize the current knowledge of skin diseases and conditions associated with rickets.

METHODS

To examine the association between rickets and skin diseases, we performed a systematic review of the literature using PubMed database. The search included studies published from the database inception to August 2019.

RESULTS

A total number of 75 articles were included. Identified conditions associated with rickets were ichthyosis being a more common skin diseases, alopecia, epidermal and melanocytic nevi, xeroderma pigmentosum, mastocytosis, psoriasis, and atopic dermatitis. Three types of rickets were identified: vitamin D-dependent rickets, hypocalcemic vitamin D-dependent rickets type 2, and hypophosphatemic rickets. Cutaneous skeletal hypophosphatemia syndrome is a newly described and under-recognized condition. It is defined by the association of epidermal or melanocytic nevi, hypophosphatemic rickets, and elevated levels of fibroblast growth factor 23. Rickets in patients with ichthyosis was mainly due to impaired ability of ichthyotic skin to synthesize vitamin D, poor UV penetration of the skin caused by keratinocyte proliferation, and dark phototype. The latter may be considered a risk factor for rickets in patients with ichthyosis.

CONCLUSION

Despite its rarity, these associations should be properly recognized by dermatologists. Early diagnosis of rickets is important to prevent growth retardation and skeletal deformities.

Hereditary vitamin D-resistant rickets: a report of four cases with two novel variants in the VDR gene and successful use of intermittent intravenous calcium via a peripheral route

Background Hereditary vitamin D-resistant rickets (HVDRR) is caused by vitamin D receptor (VDR) defects. Patients with HVDRR do not respond to standard doses of calcitriol and oral calcium (Ca) treatment and need to be treated with intravenous Ca (IV-Ca) via a central route. However, central catheter-related complications can cause significant morbidity. Case presentation Four unrelated patients with HVDRR presenting with rickets and alopecia totalis were administered intermittent IV-Ca treatment (2-5 times/week) through a peripheral route. No complications such as infection, extravasation or arrhythmias were detected upon peripheral infusion. Peripheral 1-22 months' duration of IV-Ca normalized parathyroid hormone (PTH) and alkaline phosphatase (ALP) in all patients, after which, oral Ca of 200-400 mg/kg/day and calcitriol of 0.5 μg/kg/day were sufficient to maintain normal PTH levels. Molecular studies on the VDR gene showed a previously reported homozygous c.454C > T (p.Q152*) pathogenic variant in two patients. Two novel homozygous variants in the other two patients were detected: (1) c.756-2A > G, which affects the splice acceptor site, and (2) c.66dupG (p.I23Dfs*20) variant leading to a frameshift that results in a premature stop codon. Conclusions Peripheral IV-Ca treatment is an effective and practical alternative treatment mode that provides dramatic clinical benefit in patients with HVDRR.

Experience of intravenous calcium treatment and long-term responses to treatment in a patient with hereditary vitamin D-resistant rickets resulting from a novel mutation

Background Vitamin D resistant rickets (HVDRR), is a rare autosomal recessive disorder caused by vitamin D receptor (VDR) gene mutations. There is no standard treatment in HVDRR. Case report The patient was a 3-year-old girl presenting with short stature, genu varum deformity, waddling gait and alopecia. She had hypocalcemia, hypophosphatemia, hyperparathyroidism and normal 1.25-(OH)2D levels. The patient was initially treated with calcitriol and high-dose oral calcium (Ca) for 22 months. The patient was treated with continuous high dose intravenous (i.v.) Ca therapy for 4 months, following initial lack of response to oral Ca and calsitriol. At the end of the 4 months, rickets was dramatically improved and did not recur for 3 years after i.v. Ca therapy. DNA sequence analyses of the VDR gene showed a homozygous novel mutation. Conclusions We identified a novel VDR gene mutation, and we concluded that i.v. Ca therapy from the central catheter is a safe treatment in HVDRR.

Genetic Causes of Rickets

Rickets is a metabolic bone disease that develops as a result of inadequate mineralization of growing bone due to disruption of calcium, phosphorus and/or vitamin D metabolism. Nutritional rickets remains a significant child health problem in developing countries. In addition, several rare genetic causes of rickets have also been described, which can be divided into two groups. The first group consists of genetic disorders of vitamin D biosynthesis and action, such as vitamin D-dependent rickets type 1A (VDDR1A), vitamin D-dependent rickets type 1B (VDDR1B), vitamin D-dependent rickets type 2A (VDDR2A), and vitamin D-dependent rickets type 2B (VDDR2B). The second group involves genetic disorders of excessive renal phosphate loss (hereditary hypophosphatemic rickets) due to impairment in renal tubular phosphate reabsorption as a result of FGF23-related or FGF23-independent causes. In this review, we focus on clinical, laboratory and genetic characteristics of various types of hereditary rickets as well as differential diagnosis and treatment approaches.

The Effectiveness of Cinacalcet as an Adjunctive Therapy for Hereditary 1,25 Dihydroxyvitamin D3-Resistant Rickets

High doses of oral calcium or long-term calcium infusions are recommended to correct the hypocalcemia and secondary hyperparathyroidism in patients with hereditary 1,25 dihydroxyvitamin D3-resistant rickets (HVDRR). Preliminary studies revealed that calcimimetics may be a safe and effective therapeutic choice in children with secondary hyperparathyroidism. Our aim was to observe the efficacy of cinacalcet in the normalization of secondary hyperparathyroidism and hypophosphatemia in two siblings aged 2.5 years and 6 months with HVDRR who did not respond to traditional treatment regimes. Both patients were admitted to the hospital with severe hypocalcemia. They were treated with high doses of calcitriol and calcium infusions intravenously. Secondary hyperparathyroidism was normalized temporarily, but did not improve completely. Cinacalcet (0.25 mg/kg) once a day along with the high doses of oral calcium and calcitriol was added to the treatment schedule. After 3 months, biochemical and radiologic findings reverted to normal. Our findings indicate that cinacalcet is effective in normalizing the hyperparathyroidism and hypophosphatemia in these cases and in improving the bone pathology.

Peripherally inserted central catheters for calcium requirements after successful parathyroidectomy: a comparison with centrally inserted catheters

BACKGROUND Intravenous calcium supplements are often required following parathyroidectomy to avoid postoperative hypocalcaemia. The aim of this study was to compare application effect of a femoral central venous catheter (CVC) and peripherally inserted central catheter (PICC) on intravenous calcium supplements after parathyroidectomy. METHODS We retrospectively reviewed the hospital records of 73 patients with secondary hyperparathyroidism who underwent a successful parathyroidectomy at the Huashan Hospital attached to Fudan University between 1 April 2011 and 1 February 2016. RESULTS Of the 73 study participants, 39 (53.4%) had a PICC and 34 (46.6%) had a CVC, respectively. Patients in the CVC group needed 6-7 days of intravenous calcium supplements, while patients in PICC group needed only 2-3 days to achieve normal serum calcium concentration (2.2-2.6 mmol/L). Furthermore, the duration of calcium supplementation was 71.62 ± 4.48 hours in PICC group and 100.4 ± 5.43 hours in CVC group (P < 0.05). Of the patients in PICC group, the incidence of catheter occlusion, operation failure and hypocalcaemia was 0%, which was significantly lower than those in CVC group (2.56%, 7.69% and 7.69%, respectively). CONCLUSIONS PICC is a safe and efficient alternative in contrast to CVC for providing venous access for calcium supplementation in surgical patients after parathyroidectomy.