Vitamin D metabolites in idiopathic infantile hypercalcaemia

Williams syndrome: an historical perspective of its evolution, natural history, and etiology

This review examines the Williams syndrome (WS) from an historical perspective, beginning with the early descriptions of idiopathic infantile hypercalcemia (IIH) and ending with some speculative ideas about a possible causative function of a recently discovered neuropeptide. The earliest reports of WS individuals are probably those which describe a "severe" subgroup of IIH and separate it from the epidemic of milder IIH reported in Post-WWII Great Britain and Europe. Most of these latter cases apparently resulted from hypervitaminosis D produced by excessive supplementation of government-supplied infant foods. With more extensive recognition and reporting of this "severe" subgroup, the diagnostic constellation of IIH, mental deficiency, elfin face, and supravalvular aortic stenosis (SVAS) evolved as WS. More of these reports emphasized the physical and behavioral manifestations as the key diagnostic features, and the frequency of occurrence and relative importance of SVAS and IIH in WS decreased. Despite the diminished consequence of hypercalcemia, calcium and vitamin D have continued to dominate the investigation of the cause of infantile hypercalcemia and led to the proposal and confirmation of deficient calcitonin secretion in individuals with WS. Though calcitonin is probably pertinent only to infantile hypercalcemia, its alternative gene product, calcitonin-gene-related product, is an important neuropeptide with physiological effects in the central nervous system and cardiovascular systems which raise the possibility that it may be responsible for some of the manifestations of WS.

Perinatal calcium metabolism: physiology and pathophysiology

Disturbances in mineral homeostasis are common in the neonatal period, especially in premature infants and infants who are hospitalised in an intensive care unit. In many cases these disturbances are thought to be exaggerated responses to the normal physiological transition from the intrauterine environment to neonatal independence. By contrast, some disturbances in calcium homeostasis are the result of genetic defects, which in many instances can now be identified at the molecular level. In other cases hypocalcaemia or hypercalcaemia may result from pathological intrauterine conditions, birth trauma or stress, or fetal immaturity. Diagnosis and management of hypocalcaemia and hypercalcaemia in the neonate and infant requires specific knowledge of perinatal mineral physiology and the unique clinical and biochemical features of newborn mineral metabolism. In this chapter we will provide a brief overview of calcium metabolism with an emphasis on the neonatal transition, followed by discussion of the common causes of hypercalcaemia and hypocalcaemia.

Symptomatic hypercalcemia in the first months of life: calcium-regulating hormones and treatment

Neonatal hypercalcemia is a rare condition often of unclear pathogenesis. If unrecognized and untreated it may result in central nervous system and renal damage. We studied three infants with symptomatic neonatal hypercalcemia pointing out pathogenetic and therapeutic aspects. One infant was found to have transient hyperparathyroidism with high intact parathyroid hormone (iPTH) levels. One infant had an incomplete form of Williams syndrome with hypercalcemia and an elfin facies. The pathogenesis is unclear in this case. A reduced secretion of calcitonin or an hypersensitivity to vitamin D might be the underlying defect. The third case was found to have subcutaneous fat necrosis and hypercalcemia associated with high 1,25(OH)2D levels and suppressed iPTH levels. These findings suggest an unregulated extrarenal 1,25(OH)2D production. These infants were treated with hydratation, furosemide, corticosteroids and low calcium diet. Symptomatic neonatal hypercalcemia should be treated promptly. However blood has to be taken before starting treatment to study calcium-regulating hormones and clarify pathogenesis.

Williams-Beuren syndrome: an update and review for the primary physician

Williams-Beuren syndrome is an autosomal dominant disorder resulting from a submicroscopic deletion of contiguous genes on the long arm of chromosome 7. It consists of a variety of hallmark physical features, which include distinctive facial characteristics, cardiac anomalies (of which the most common is supravalvular aortic stenosis), and occasional idiopathic hypercalcemia. The condition also includes a unique cognitive profile, with relative sparing of language and facial recognition skills against a background of mental retardation. This paper reviews the early history and clinical experience with this syndrome, how it unfolds from infancy through adulthood, and how it manifests in different organ systems. Evidence-based recommendations are then offered for the treatment of the specific developmental and medical issues that arise in patients with Williams syndrome.

The spectrum of ocular features in the Williams-Beuren syndrome

One hundred and fifty-two patients with the Williams-Beuren syndrome were examined to assess the frequency and severity of ophthalmological features associated with the disorder. Eighty-two (54%) had strabismus, all but three, esotropia. One hundred and seventeen (77%) patients had blue irides, 10 (7%) green, and 25 (16%) brown. One hundred and twelve (74%) showed a typical so-called stellate iris pattern of the anterior stroma. Whitish anomalies were also detectable in brown irides. Two 9-year-old patients and one 46-year-old patient had initial cataract. Of all the patients with funduscopy, 22% had retinal vascular tortuosity. One patient had suspected Rieger syndrome. Two patients had ptosis, one with a Marcus-Gunn phenomenon. No ocular manifestation of hypercalcaemia was noted.

Idiopathic infantile hypercalcemia discovered in the newborn period

We report a male newborn with typical clinical signs of idiopathic infantile hypercalcemia (IIH); that is, hypercalcemia, hypercalciuria, an elfin face and nephrocalcinosis without giving Vitamin D3 supplementation to the patient. He had been treated with a vitamin D-free, low calcium milk and rectal administration of exogenous calcitonin (elcatonin). The latter seemed to be more effective as a treatment for IIH. The serum calcium level came within the normal range and the serum 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) level decreased from 101.5 to 75.6 pg/mL with the treatments mentioned above. These results suggest that a high serum concentration of 1,25(OH)2D3 is part of the pathogenesis of IIH. However, we were not able to clarify the pathogenesis of the high serum concentration of 1,25(OH)2D3.

Dermatoglyphic peculiarities in patients with Williams-Beuren syndrome

The dermatoglyphic patterns of fingertips and palms of 115 patients with Williams-Beuren syndrome (WBS) were analysed and compared with the data from 199 control individuals from Germany. The following combination of dermatoglyphic patterns appears to be characteristic to WBS: an excess of whorls on all fingertips; high termination values of the main lines D, B, and A; frequent absence of C triradius (C0); high frequencies of ulnar loops on the hypothenar and distal loops on the 2nd, 3rd, and 4th interdigital areas, of distal axial triradii t", and of abnormal palmar creases such as simian crease and Sydney lines. The combination of fingertip and palmar patterns expressed by a "Log.Score-Index," provides a high degree of discrimination between the WBS patients (92%) and the control group (88%). A "phantom picture" for WBS was constructed, which can be used for its diagnosis.

Calcium metabolism in Williams-Beuren syndrome

Increased 1,25-dihydroxyvitamin D levels and decreased basal and calcium-stimulated calcitonin serum levels have been found in children with Williams-Beuren syndrome (WBS). To determine whether isolated or combined disturbances of secretion or action of the calcium-regulating hormones may cause the tendency to hypercalcemia in WBS, we investigated several aspects of calcium metabolism in 27 normocalcemic children and adults, aged 2 to 47 years, with WBS. With the exception of slightly decreased 25-hydroxyvitamin D and slightly increased calcitonin in serum, all measured basal indexes of calcium and bone metabolism, including the serum levels of intact parathyroid hormone and 1,25-dihydroxyvitamin D, were comparable to control values. Total and extractable calcitonin, the latter representing the monomeric and biologically important form of the hormone, showed the same relative increase after a low-dose calcium infusion in patients and control subjects, indicating a normal capacity of the calcitonin-producing C cells of the thyroid gland in WBS. Furthermore, exogenous parathyroid hormone induced a normal response of 1,25-dihydroxyvitamin D, cyclic adenosine monophosphate, and phosphate excretion, indicating a normal response of the renal 25-hydroxyvitamin D-1 alpha-hydroxylase and the renal receptor-adenylate cyclase system to parathyroid hormone. These findings suggest that neither deficient calcitonin secretion nor increased renal sensitivity to parathyroid hormone is a feature of WBS in normocalcemic patients.

Ionized calcium: pediatric perspective

Ionized calcium is a physiologically critical calcium pool. It is easily determined, although accuracy depends on sample handling. As a clinical parameter, directly measured ionized calcium has particular import in the care of neonates, patients with sepsis or other cardiovascular instability, massively transfused patients, and those undergoing cardiopulmonary bypass or liver transplantation. Disturbances of calcium occur in many other settings, however, and accurate diagnosis and research conclusions may depend on using the best measurement available. Clinical and investigational use of ionized calcium determinations represent appropriate applications of current proven technology. In the future, clinical calcium manipulation may include modifying specific transmembrane transport processes and intracellular calcium pools and movements. At the current time we are largely restricted to studies of extracellular calcium concentration and its interactions. Much is known, but Mother Nature still has too many secrets. The interested reader is referred to discussions of ionized calcium and hemodynamics, reviews of the endocrine disturbances of calcium and phosphorus, textbook discussions pertinent to general calcium disturbances, and critical care issues.

A survey of adults with Williams syndrome and idiopathic infantile hypercalcaemia

Questionnaires completed by the caregivers of 119 adults with Williams syndrome or idiopathic infantile hypercalcaemia gave information on current living arrangements, daytime occupations and attainments, self-care skills, social relationships, behavioural and adjustment difficulties and the impact of Williams syndrome and idiopathic infantile hypercalcaemia on caregivers and their families. Many were reported to have marked behavioural and social difficulties persisting into adulthood, and most required some supervision and support in everyday activities such as dressing, toileting and preparing food. Some caregivers were dissatisfied with the level of educational attainment, current daytime occupations and support received from professionals. Over half were concerned about future living arrangements and daytime occupations. Comparisons between the questionnaires for the two groups revealed no phenotypical differences in their abilities or behavioural characteristics.

Dysmorphic syndromes with demonstrable biochemical abnormalities

Many inborn errors of metabolism are associated with dysmorphic manifestations. In this review, we have attempted to correlate the dysmorphic features with the underlying metabolic defect or its consequences. Most of the defects which we have discussed affect the synthesis or degradation of macromolecules (for example, collagen, elastin, bone mineral, proteoglycans, glycoproteins, and triglycerides). Such defects may affect either a single enzyme or multiple enzymes in specific organelles, such as lysosomes or peroxisomes, or they may affect hormonal control of synthesis and degradation. Examples are also included of defects affecting the catabolism of simple molecules when accumulating metabolites have a secondary effect on macromolecules, as in homocystinuria. In a number of instances, however, the correlation between the biochemical abnormality and the dysmorphic features are not understood. Ultimately, all dysmorphic syndromes will be attributable to a biochemical defect or its effects. The aim of this overview is to provide an insight into the relationship between the two at the present time.

Elevated 1,25-dihydroxyvitamin D and normocalcaemia in presumed familial Williams syndrome

Two brothers with Williams syndrome without hypercalcaemia are presented. One boy died during the first month of life. His brother also had the typical phenotypic features of the elfin facies. He developed severe microcephaly and cataract and died at the age of 9 years. The skeleton was osteosclerotic at birth, and became generally osteoporotic at the age of 2 years. He had persistently elevated 1,25-dihydroxyvitamin D levels during the first 2 years of life, in spite of normocalcaemia. At autopsy, microcalcifications were found in the brain and kidneys. The present report underscores the familial occurrence of Williams syndrome of severe degree. Elevated 1,25-dihydroxyvitamin D levels without hypercalcaemia have not been reported previously, and may suggest causal heterogeneity of the Williams syndrome.

Age at diagnosis and abilities in idiopathic hypercalcaemia

Forty three children aged 6 to 16 years with a documented history of idiopathic infantile hypercalcaemia were assessed on a variety of cognitive and behavioural measures. No relation was found between the age at which hypercalcaemia was diagnosed and subsequent full scale intelligence quotients (IQ) and reading or spelling abilities. Verbal IQ was, however, significantly higher than performance IQ, which had an inverse relation with age at diagnosis. Furthermore, scores for deviant behaviour were found to correlate with age at diagnosis. Thus the characteristic psychological profile of this syndrome may be in part a function of hypercalcaemia during infancy.