Rickets in an infant with Williams syndrome

Growth, body composition, and endocrine issues in Williams syndrome

PURPOSE OF REVIEW

Williams syndrome is a multisystem disorder caused by a microdeletion on chromosome 7q. Throughout infancy, childhood, and adulthood, abnormalities in body composition and in multiple endocrine axes may arise for individuals with Williams syndrome. This review describes the current literature regarding growth, body composition, and endocrine issues in Williams syndrome with recommendations for surveillance and management by the endocrinologist, geneticist, or primary care physician.

RECENT FINDINGS

In addition to known abnormalities in stature, calcium metabolism, and thyroid function, individuals with Williams syndrome are increasingly recognized to have low bone mineral density, increased body fat, and decreased muscle mass. Furthermore, recent literature identifies a high prevalence of diabetes and obesity starting in adolescence, and, less commonly, a lipedema phenotype in both male and female individuals. Understanding of the mechanisms by which haploinsufficiency of genes in the Williams syndrome-deleted region contributes to the multisystem phenotype of Williams syndrome continues to evolve.

SUMMARY

Multiple abnormalities in growth, body composition, and endocrine axes may manifest in individuals with Williams syndrome. Individuals with Williams syndrome should have routine surveillance for these issues in either the primary care setting or by an endocrinologist or geneticist.

Hypercalcemia in Patients with Williams-Beuren Syndrome

OBJECTIVE

To evaluate the timing, trajectory, and implications of hypercalcemia in Williams-Beuren syndrome (WBS) through a multicenter retrospective study.

STUDY DESIGN

Data on plasma calcium levels from 232 subjects with WBS aged 0-67.1 years were compared with that in controls and also with available normative data. Association testing was used to identify relevant comorbidities.

RESULTS

On average, individuals with WBS had higher plasma calcium levels than controls, but 86.7% of values were normal. Nonpediatric laboratories overreport hypercalcemia in small children. When pediatric reference intervals were applied, the occurrence of hypercalcemia dropped by 51% in infants and by 38% in toddlers. Across all ages, 6.1% of the subjects had actionable hypercalcemia. In children, actionable hypercalcemia was seen in those aged 5-25 months. In older individuals, actionable hypercalcemia was often secondary to another disease process. Evidence of dehydration, hypercalciuria, and nephrocalcinosis were common in both groups. Future hypercalcemia could not be reliably predicted by screening calcium levels. A subgroup analysis of 91 subjects found no associations between hypercalcemia and cardiovascular disease, gastrointestinal complaints, or renal anomalies. Analyses of electrogradiography data showed an inverse correlation of calcium concentration with corrected QT interval, but no acute life-threatening events were reported.

CONCLUSIONS

Actionable hypercalcemia in patients with WBS occurs infrequently. Although irritability and lethargy were commonly reported, no mortality or acute life-threatening events were associated with hypercalcemia and the only statistically associated morbidities were dehydration, hypercalciuria, and nephrocalcinosis.

Late-onset hypercalcemia in Williams-Beuren syndrome: importance of early and frequent screening and intervention

Williams-Beuren syndrome (WBS) affects multiple systems and has a known association with infantile hypercalcemia that is typically mild and transient. We report a 12-month-old female previously diagnosed with WBS by a chromosomal microarray, who was admitted for failure to thrive. Upon evaluation, serum calcium of 19.0 mg/dL (4.75 mmol/L) (normal 9-11 mg/dL, SI: 2.25-2.75 mmol/L) and serum ionized calcium of 2.33 mmol/L (normal 1.22-1.37 mmol/L) were revealed. Her hypercalcemia correlated with symptoms of irritability, poor feeding, mild hypotonia, and constipation, which were increasingly present for 6 months prior to admission. This calcium level is one of the highest reported in association with WBS. Additionally, while hypercalcemia associated with WBS typically resolves by the first year, this case represents a later presentation as compared to other reports. The patient initially responded to conservative treatment with intravenous fluids administration, loop diuretic therapy, and dietary calcium restriction. However, she subsequently had rebound hypercalcemia 5 weeks after treatment and received one dose of intravenous bisphosphonate with subsequent resolution of her hypercalcemia. Our report highlights the importance of screening, early management, and recognition of late presentation hypercalcemia in the setting of WBS.

Vitamin D supplementation during pregnancy: double-blind, randomized clinical trial of safety and effectiveness

The need, safety, and effectiveness of vitamin D supplementation during pregnancy remain controversial. In this randomized, controlled trial, women with a singleton pregnancy at 12 to 16 weeks' gestation received 400, 2000, or 4000 IU of vitamin D(3) per day until delivery. The primary outcome was maternal/neonatal circulating 25-hydroxyvitamin D [25(OH)D] concentration at delivery, with secondary outcomes of a 25(OH)D concentration of 80 nmol/L or greater achieved and the 25(OH)D concentration required to achieve maximal 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] production. Of the 494 women enrolled, 350 women continued until delivery: Mean 25(OH)D concentrations by group at delivery and 1 month before delivery were significantly different (p < 0.0001), and the percent who achieved sufficiency was significantly different by group, greatest in 4000-IU group (p < 0.0001). The relative risk (RR) for achieving a concentration of 80 nmol/L or greater within 1 month of delivery was significantly different between the 2000- and the 400-IU groups (RR = 1.52, 95% CI 1.24-1.86), the 4000- and the 400-IU groups (RR = 1.60, 95% CI 1.32-1.95) but not between the 4000- and. 2000-IU groups (RR = 1.06, 95% CI 0.93-1.19). Circulating 25(OH)D had a direct influence on circulating 1,25(OH)(2)D(3) concentrations throughout pregnancy (p < 0.0001), with maximal production of 1,25(OH)(2)D(3) in all strata in the 4000-IU group. There were no differences between groups on any safety measure. Not a single adverse event was attributed to vitamin D supplementation or circulating 25(OH)D levels. It is concluded that vitamin D supplementation of 4000 IU/d for pregnant women is safe and most effective in achieving sufficiency in all women and their neonates regardless of race, whereas the current estimated average requirement is comparatively ineffective at achieving adequate circulating 25(OH)D concentrations, especially in African Americans.

Nephrocalcinosis in preterm neonates

The prevalence of nephrocalcinosis (NC) in preterm neonates in recent reports is 7-41%. The wide range in prevalence is a consequence of different study populations and ultrasound equipment and criteria, in addition to a moderate interobserver variation. NC in preterm neonates has a multifactorial aetiology, consisting of low gestational age and birth weight, often in combination with severe respiratory disease, and occurs as a result of an imbalance between stone-promoting and stone-inhibiting factors. A limited number of histological studies suggest that calcium oxalate crystals play an important role in NC in premature neonates. In 85% of children resolution of NC occurs in the first years of life. Prematurity, per se, is associated with high blood pressure, relatively small kidneys, and (distal) tubular dysfunction. In addition, NC in preterm neonates can have long-term sequelae for glomerular and tubular function. Long-term follow-up of blood pressure and renal function of prematurely born children, especially with neonatal NC, is recommended. Prevention of NC with (low) oral doses of citrate has not resulted in a significant decrease in the prevalence of NC; a higher citrate dosage deserves further study. Future research pertaining to prevention of NC in preterm neonates is crucial.

The effect of high-dose vitamin D supplementation on serum vitamin D levels and milk calcium concentration in lactating women and their infants

OBJECTIVE

Improve vitamin D status in lactating women and their recipient infants, and measure breast milk calcium concentration [Ca] as a function of vitamin D regimen.

DESIGN/METHODS

Fully breastfeeding mothers were randomized at 1 month postpartum to 2000 (n = 12) or 4000 (n = 13) IU/day vitamin D for 3 months to achieve optimal vitamin D status [serum 25(OH)D > or =32 ng/mL (80 nmol/L)]. Breast milk [Ca], maternal and infant serum 25(OH)D and serum Ca, and maternal urinary Ca/Cr ratio were measured monthly.

RESULTS

Mothers were similar between groups for age, race, gestation, and birth weight. 25(OH)D increased from 1 to 4 months in both groups (mean +/- SD): +11.5 +/- 2.3 ng/mL for group 2000 (p = 0.002) and +14.4 +/- 3.0 ng/mL for group 4000 (p = 0.0008). The 4000 IU/day regimen was more effective in raising both maternal and infant serum levels and breast milk antirachitic activity than the 2000 IU/day regimen. Breast milk [Ca] fell with continued lactation through 4 months in the 2000 and 4000 IU groups. Decline in breast milk [Ca] was not associated with vitamin D dose (p = 0.73) or maternal 25(OH)D (p = 0.94). No mother or infant experienced vitamin D-related adverse events, and all laboratory parameters remained in the normal range.

CONCLUSION

High-dose vitamin D was effective in increasing 25(OH)D levels in fully breastfeeding mothers to optimal levels without evidence of toxicity. Breast milk [Ca] and its decline in both groups during 1 to 4 months were independent of maternal vitamin D status and regimen. Both the mother and her infant attained improved vitamin D status and maintained normal [Ca].

Genetic Hypercalciuria

Hypercalciuria is an important, identifiable, and reversible risk factor in stone formation. The foremost and most fundamental step in dissecting the genetics of hypercalciuria is understanding its pathophysiology. Hypercalciuria is a complex trait. This article outlines the various factors that compromise the attempt to dissect the genetics of hypercalciuria, summarizes the clinical and experimental monogenic causes of hypercalciuria, and outlines the initial results from attempts in studying polygenic hypercalciuria. Finally, the problem is set in perspective of the current database, technologic advances and limitations are highlighted, and prospects of further advances in the field are speculated upon.

Severe infantile hypercalcemia associated with Williams syndrome successfully treated with intravenously administered pamidronate

Infantile hypercalcemia occurs in approximately 15% of children with Williams syndrome (WS) and is typically not clinically severe. We report on 3 children with WS (confirmed with fluorescent in situ hybridization probes) who presented with severe symptomatic hypercalcemia. The first patient's severe hypercalcemia resolved with traditional therapies, whereas the subsequent 2 patients were treated with intravenously administered pamidronate after traditional measures proved only partially successful. Besides asymptomatic mild hypocalcemia, there were no complications resulting from pamidronate administration. We conclude that WS-associated hypercalcemia can be quite severe and symptomatic and that it can be successfully and safely treated with intravenously administered bisphosphonate in some cases.

Urinary L-lactate excretion is increased in renal Fanconi syndrome

BACKGROUND

Measurement of l-lactate in body fluids is an established clinical tool to identify disorders of cellular respiration. However, there is very little known about the clinical value of urinary lactate measurements. We investigated urinary lactate excretion in children with renal Fanconi syndrome.

METHODS

Freshly voided urine samples were obtained from children with Fanconi syndrome and controls both with and without renal disease. Urine lactate was estimated by conversion to pyruvate in the presence of lactate dehydrogenase and NAD. The NADH produced was measured photometrically. Urine lactate was factored for urine creatinine.

RESULTS

Children with Fanconi syndrome had a significantly higher urine lactate/creatinine ratio [mean: 84 x 10(-2) mmol/mmol; 95% confidence interval (CI): 40.8-127.1 x 10(-2) mmol/mmol] than healthy controls (mean: 1.3 x 10(-2) mmol/mmol; CI: 1.1-1.5 x 10(-2) mmol/ mmol) and those with a variety of renal diseases (mean: 3.1 x 10(-2) mmol/mmol; CI: 1.8-4.5 x 10(-2) mmol/mmol).

CONCLUSIONS

Urinary lactate is increased in Fanconi syndrome. The increase is likely to be due to reduced lactate co-transport in the proximal tubule. Urinary lactate/creatinine has clinical utility as a sensitive test of disordered proximal renal tubular function.