Background The rate of non-compliance with vitamin D supplementation is as high as 45%. This is why randomised controlled trials are needed to analyse the response to low doses of vitamin D3. Objective (1) To compare supplementation with 250 versus 500 units of vitamin D3 and (2) to analyse sun exposure time/ultraviolet B (UVB) exposure during the first 6 weeks of life. Design 40 breastfed infants (skin photo-types I, II) were recruited in Berlin, Germany (52.5°N), during summer (n=20) and winter (n=20) and randomised into equal groups on either 250 or 500 units of vitamin D3 per day. Outcome measures were: parameters of vitamin D and bone metabolism at delivery and 6 weeks later, sun exposure time, UVB dosimetry and surrounding factors including maternal diet. Results At delivery 25-hydroxy vitamin D levels were insufficient: 68 (53–83) nmol/l in each group. 6 weeks later levels were sufficient: 139 (114–164) nmol/l on 250 units of vitamin D3 per day and 151 (126–176) nmol/l on 500 units/day. There was no seasonal variation. Daily sun exposure time was 0.4–3.5 h and higher in summer. UVB exposure was 0.01–0.08 minimal erythema dose/day. Calcium levels were within normal. Conclusions In Berlin, Germany, supplementation with 250 units of vitamin D3 is sufficient for breastfed infants during their first 6 weeks of life in summer and winter. UVB exposure is very low throughout the year.

Lower vitamin D status at birth and during infancy has been associated with increased incidence of eczema and food allergies. The aim of this study was to investigate the effect of early infancy vitamin D supplementation on allergic disease outcomes in infants at “hereditary risk” of allergic disease, but who had sufficient vitamin D levels at birth. Here, we report the early childhood follow-up to 2.5 years of age of “high-risk” infants who participated in a double-blinded, randomized controlled trial. For inclusion in this trial, late gestation (36–40 weeks) maternal 25-hydroxyvitamin D levels needed to be ≥50 nmol/L. Infants were randomized to either oral vitamin D supplementation of 400 IU/day (n = 97) or a placebo (n = 98) for the first six months of life. Vitamin D levels and allergic disease outcomes were followed up. There were no statistically significant differences in incidence of any medically diagnosed allergic disease outcomes or allergen sensitization rates between the vitamin D-supplemented and placebo groups at either 1 year or at 2.5 years of age. In conclusion, for “allergy high-risk” infants who had sufficient vitamin D status at birth, early infancy oral vitamin D supplementation does not appear to reduce the development of early childhood allergic disease.

X‐linked hypophosphataemia (XLH), the most common inherited form of rickets, is caused by a PHEX gene mutation that leads to excessive serum levels of fibroblast growth factor 23 (FGF23). This leads to clinical manifestations such as rickets, osteomalacia, pain, lower limb deformity and overall diminished quality of life. The overarching aims in the management of children with XLH are to improve quality of life by reducing overall burden of disease, optimise an individual's participation in daily activities and promote normal physical and psychological development. Burosumab, a monoclonal antibody targeting FGF23, has been shown to improve biochemistry, pain, function and radiological features of rickets in children with XLH and has transformed management of XLH around the world. Burosumab has been recently approved for clinical use in children with XLH in Australia. This manuscript outlines a clinical practice guideline for the use of burosumab in children with XLH to assist local clinicians, encourage consistency of management across Australia and suggest future directions for management and research. This guideline also strongly advocates for all patients with XLH to have multidisciplinary team involvement to ensure optimal care outcomes and highlights the need to consider other aspects of care for XLH in the era of burosumab, including transition to adult care and the effective coordination of care between local health‐care providers and specialist services.

The dramatic rise in allergic disease has occurred in tandem with recent environmental changes and increasing indoor lifestyle culture. While multifactorial, one consistent allergy risk factor has been reduced sunlight exposure. However, vitamin D supplementation studies have been disappointing in preventing allergy, raising possible independent effects of ultraviolet (UV) light exposure. The aim of this study was to examine whether UV light exposure influences the development of allergic disease in early childhood. Direct sunlight exposure (290–380 nm) in early infancy was measured via UV dosimeters. Outdoor exposure, sun protective behaviours, and allergy outcomes were assessed over the first 2.5 years of life with clinical assessment appointments at 3, 6, 12 and 30 months of age. Children with eczema had less (p = 0.038) direct UV light exposure between 0–3 months of age (median (IQR) 747 (473–1439) J/m²) than children without eczema (median (IQR) 1204 (1717–1843) J/m²); and less outdoor exposure time (7 min/day) between 11 a.m. and 3 p.m. compared to children without eczema (20 min/day, p = 0.011). These associations were seen independent of vitamin D status, and after adjusting for other potential confounders. Whilst we could not find any associations between direct UV light exposure and other allergic disease outcomes, exposure to UV light appears to be beneficial in reducing the risk of eczema development in early childhood. Further research is required to determine optimal levels of UV light exposure while balancing the potential risks.

Hyperinsulinaemic hypoglycaemia (HH) is characterised by inappropriate insulin secretion and is the most common cause for persistent neonatal hypoglycaemia. The only treatment available for medically unresponsive hypoglycaemia is a near-total pancreatectomy. A neonate with severe HH, due to a homozygous ABCC8 mutation, was not responsive to treatment with maximal doses of diazoxide and subcutaneous daily octreotide, and underwent a near-total pancreatectomy; however, hypoglycaemia persisted. Introduction of sirolimus, an mTOR (mammalian target of rapamycin) inhibitor, obviated the requirement for glucose infusion. Euglycaemia was achieved with no significant adverse events from the drug. Sirolimus therapy was ceased at 13 months of age. No episodes of persistent hypoglycaemia were observed after cessation of sirolimus. This report demonstrates the successful use of sirolimus for persistent hypoglycaemia in the critically ill infant post pancreatectomy. Sirolimus could be considered in patients with severe HH not responsive to conventional medical and surgical therapy. However, the long-term efficacy and safety with this immunosuppressive drug in very young patients are not assured.