Impaired calcium homeostasis in the infantile hypercalcemic syndrome

Involvement of claudin 3 and claudin 4 in idiopathic infantile hypercalcaemia: a novel hypothesis?

BACKGROUND

Idiopathic infantile hypercalcaemia (IIH) is a rare disease that generally resolves spontaneously between the age of 1 and 3 years. Similar symptoms may occur in patients suffering from Williams-Beuren syndrome (WBS), which is caused by a microdeletion on chromosome 7. Two of the genes, named CLDN3 and CLDN4, located within this region are members of the claudin family that has been shown to be involved in paracellular calcium (Ca(2+)) absorption. Based on the hemizygous loss of CLDN3 and CLDN4 in WBS and the function of these genes in paracellular Ca(2+) transport, we hypothesized that mutations in CLDN3 or CLDN4 could also be involved in IIH.

METHODS

Biochemical characteristics, including calciotropic hormone levels, were obtained from three typical IIH patients. CLDN3 and CLDN4 sequences were also analysed in these patients. The major intestinal Ca(2+) transporter TRPV6 was also screened for the presence of mutations, since hypercalcaemia in IIH and WBS has been shown to result from intestinal hyperabsorption. All three patients were also analysed for the presence of deletions or duplications using a single-nucleotide polymorphism (SNP) array for genomic DNA.

RESULTS

The serum Ca(2+) levels of patients were 2.9, 3.3 and 3.8 mmol/L (normal <2.7 mmol/L). Levels of 25-hydroxyvitamin D(3) and 1,25-dihydroxyvitamin D(3) were normal, parathyroid hormone (PTH) and PTH-related peptide (PTHrP) levels were appropriately low. Sequencing of coding regions and intron-exon boundaries did not reveal mutations in CLDN3, CLDN4 and TRPV6. Identified SNPs were not correlated with the disease phenotype. A SNP array did not reveal genomic deletions or duplications.

CONCLUSIONS

Biochemical analysis did not reveal inappropriate levels of calciotropic hormones in IIH patients in this study. Furthermore, based on the lack of mutations in CLDN3, CLDN4 and TRPV6, we conclude that IIH is neither caused by mutations in these candidate genes nor by deletions or duplications in the genome of these patients.

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.

Long-term control of hypercalcaemia in an infant with williams-Beuren syndrome after a single infusion of biphosphonate (Pamidronate)

AIM

To report the efficacy of Pamidronate to treat hypercalcaemia in a patient with Williams-Beuren syndrome (WBS).

RESULTS

We report a 14-mo-old male infant presenting hypercalcaemia, elfin face and other dysmorphological features of WBS, confirmed by the FISH fluorescent test. Due to the marked symptomatic hypercalcaemia, 13.0 mg/dl intravenous Pamidronate was administered in a single dose of 1 mg/kg. Two days later, serum calcium diminished to normal levels, and remained within normal range during 12 mo follow-up.

CONCLUSION

Pamidronate appears to be effective in paediatric patients with WBS and hypercalcaemia.

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.

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.

Myopathy in Williams-Beuren syndrome

Williams-Beuren syndrome (WBS) is a disorder of unknown aetiology. The classical features of the syndrome include a typical ('elfin') facies, mental retardation and heart defects. Myopathy has not so far been part of the spectrum of WBS. We studied six patients with WBS aged 3-25 years, five of whom showed clinical and morphological evidence of myopathy. The clinical manifestations of myopathy included hypotonia in infancy, walking delay, joint contractures, scoliosis, and increased exhaustion on exertion. These symptoms were present in variable expression but part of a typical postural pattern. Examination of muscle biopsies showed lipid storage in four patients and increased variability of fibre size in three. In one patient a muscle biopsy gave normal results. Biochemical investigation in four patients with morphological evidence of lipid storage in muscle revealed muscle carnitine deficiency in three. In addition, enzyme activities of fatty acid beta-oxidation were low in one of two specimens tested. It is concluded that a clinically relevant myopathy is part of the multi-system manifestation of WBS and a clinical trial of carnitine supplementation is justified.

Characterization of the calcitonin/CGRP gene in Williams syndrome

We have investigated the possibility of mutations in the calcitonin/calcitonin gene related peptide (CGRP) gene in children with Williams syndrome. Involvement of the calcitonin/CGRP gene in Williams syndrome is postulated on the basis that Williams syndrome children often have infantile hypercalcemia and deficient expression of calcitonin, a hormone that lowers serum calcium levels. To test the hypothesis that mutations in the calcitonin/CGRP gene might be responsible for the reduced calcitonin levels, we examined the calcitonin/CGRP gene structure in Williams syndrome children. Analysis of white blood cell DNA by Southern blot hybridizations in 5 individuals did not show any detectable large deletions or rearrangements in the calcitonin/CGRP gene locus. The possibility of small deletions or point mutations within the exon encoding the mature calcitonin hormone is unlikely based on ribonuclease protection assays with patient DNA amplified by the polymerase chain reaction (PCR) technique. These findings suggest that the calcitonin deficiency might be due either to mutations elsewhere in the gene or to defects in the cellular machinery needed for calcitonin synthesis and/or secretion.

Parathyroid surgery in children

Parathyroid surgery in children is uncommon. Spontaneously occurring cases of hyperparathyroidism are almost always due to single-gland disease: however, on exploration all four parathyroid glands should be identified. Most of the other instances in which the surgeon needs to perform a parathyroidectomy on an infant or a child will be situations were multiple-gland disease is the rule rather than the exception. Therefore, the surgeon must have in his mind a well developed logical approach to the management of children with parathyroid disorders on the basis of multiple glandular disease. We believe that the technique of parathyroid autotransplantation very satisfactorily addresses the surgical needs of children with familial hyperparathyroid states, including the multiple endocrine neoplasias. We believe that it is mandatory treatment in patients presenting with neonatal primary hyperparathyroidism and is also the procedure of choice in children with secondary and tertiary hyperparathyroidism. The workup and diagnosis of parathyroid disorders should be familiar to the surgeon who undertakes neck exploration on children, and the entity of familial hypocalciuric hypercalcemia should be looked for, as these patients have a strong likelihood of not benefiting from parathyroidectomy.

The calcitonin-CGRP gene in the infantile hypercalcaemia/Williams-Beuren syndrome

We have investigated 13 families, each of which have one member with infantile hypercalcaemia/Williams-Beuren syndrome (IHWBS), for either a germ cell mutation of, or an association with, the calcitonin-CGRP gene. Restriction fragment mapping studies of the calcitonin-CGRP gene using five restriction enzymes (TaqI, Bg/II, PvuII, PstI, and SacI) and region specific probes failed to show any abnormalities of this gene complex. NO association of IHWBS with polymorphism of the calcitonin-CGRP/parathormone locus was found. Therefore, although the aetiology of IHWBS may be caused by a new dominant mutation, there is no evidence to implicate major rearrangements of the calcitonin-CGRP and parathormone genes.

Natural history of Williams syndrome: physical characteristics

The natural history of Williams syndrome, including medical complications, growth patterns, and problems in adulthood, was investigated. A growth pattern characterized by delay in the first 4 years of life, catch-up growth in childhood, and low ultimate adult height was found. Despite multiple medical problems in infancy, including feeding problems, failure to thrive, colic, and otitis media, mean age at diagnosis was 6.4 years. Developmental disabilities and cardiovascular disease were the major concerns in childhood. The older children developed progressive joint limitation and hypertonia. Adult patients were handicapped by their developmental disabilities. Hypertension, and gastrointestinal and genitourinary problems occurred frequently. Independent living and competitive employment were limited less by the individual's physical problems than by the psychologic and adaptive limitations. Williams syndrome is a progressive disorder with multisystem involvement.

Infantile hypercalcemia with subcutaneous fat necrosis. Report of a case with studies on the pathogenesis of hypercalcemia

A case of hypercalcemia in neonatal subcutaneous fat necrosis, which was successfully treated with a low Ca and vitamin D-free formula, is described. Low 1,25(OH)2D and severe calciuria, which were considered to result from hypercalcemia itself as well as parathyroid suppression, were noted during the hypercalcemic phase. The oral Ca load test was repeatedly normal, suggesting that intestinal hyperabsorption of Ca was not a cause of the hypercalcemia. Later recurrence of calciuria without hypercalcemia was noted concomitant with softening of indurated calcified necrotic tissue. In this patient, cerebral infarction on the left side was detected by CT scanning.

Williams syndrome

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Primary hyperparathyroidism in infancy

Primary hyperparathyroidism in the neonate is a rare and often fatal disorder. These infants typically display severe hypercalcemia, respiratory distress, muscular hypotonia, and skeletal demineralization. They are usually diagnosed within the first three months of life and have hyperplasia of the four parathyroid glands. Twenty-nine infants with primary hyperparathyroidism are reported in the literature. Mortality is 87.5% in medically managed patients and 24% in surgically managed patients. Surgical management has not been satisfactory, in that recurrent hypercalcemia has been encountered in most patients undergoing subtotal parathyroidectomy, and total parathyroidectomy has resulted in the need for lifelong calcium and vitamin D supplementation. We have recently cared for a term newborn female in whom the diagnosis of primary hyperparathyroidism was made clinically on the second day of life, and later was confirmed biochemically. The baby underwent neck exploration on the 11th day of life and was successfully treated with total parathyroidectomy and parathyroid autotransplantation. Although initially rendered eucalcemic, the infant subsequently developed recurrent hypercalcemia requiring the removal of some of the autograft. Currently, the child is more than 2 years following surgery, growing well, and off all medication. The world literature is reviewed in this report of one of the first and the youngest infants, to our knowledge, to undergo parathyroid autotransplantation. In view of its success in avoiding the complication of repeated neck exploration for recurrent hyperparathyroidism or the creation of permanent hypoparathyroidism, we recommend this surgical approach for the rare neonate with primary hyperparathyroidism.

Imparied calcitonin secretion in patients with Williams syndrome

Williams syndrome is associated with neonatal hypercalcemia of unclear pathogenesis. To learn more about the hormonal control of calcium metabolism in patients with Williams syndrome, we studied five such children, with intravenous calcium and parathyroid hormone infusions as provocative stimuli. These patients were found to have significantly higher mean baseline calcium concentrations, delayed clearance of calcium after intravenous calcium loading, and blunted calcitonin responses after calcium infusion, compared with a group of seven normal children. No abnormalities of vitamin D metabolite concentrations were found, either before or after parathyroid hormone stimulation. Our studies demonstrate that patients with Williams syndrome have a defect in the synthesis or release of immunoreactive calcitonin. A deficiency of calcitonin may explain the abnormalities of calcium metabolism seen in these patients and can serve as an important endocrine marker for Williams syndrome.

Idiopathic infantile hypercalcaemia--a continuing enigma

Seventy six children with documented Fanconi-type idiopathic infantile hypercalcaemia were studied and compared with 41 with the Williams-Beuren syndrome. Clinical comparison showed, as expected, very close similarities but also considerable differences, particularly in the severity of feeding problems and the degree of failure to thrive. The estimated incidence of idiopathic infantile hypercalcaemia alone has remained constant for the past 20 years, at approximately 18 cases per year in the United Kingdom (1 per 47 000 total live births). Long term morbidity in these children is mainly due to mental handicap and arteriopathy, but hypertension (29%), kyphoscoliosis (19%), hyperacusis (75%), and obesity (50%) may be added complications. In one child, hypercalcaemia recurred during adolescence but this seems to be excessively rare. More detailed investigation before treatment is required to discover the aetiology of hypercalcaemia in this condition.

Supravalvular aortic stenosis with parafollicular cell (C-cell) hyperplasia

Autopsy examination of a patient with well-documented supravalvular aortic stenosis and other characteristic features of the idiopathic infantile hypercalcemia syndrome revealed previously unreported hyperplasia of parafollicular cells (C cells). Immunohistochemical analysis demonstrated up to 30 calcitonin-containing cells per high power field, whereas normal glands contain only 4 to 10 cells per low power field in areas of highest concentration. The parathyroid glands were found to be normal both grossly and microscopically, whereas the bones showed thickened trabeculas, normal Haversian canals and no apparent increase in osteoblast or osteoclast activity, suggesting normal parathyroid hormone, but increased thyrocalcitonin activity. We suggest that C-cell hyperplasia has occurred in response to a persistent, rather than transient, elevation in serum calcium levels and that thyrocalcitonin function is augmented, rather than impaired in this disorder. The primary biochemical defect promoting hypercalcemia remains to be clarified, as well as the role, if any, such a defect plays in producing significant pathology in the central nervous system and in the cardiovascular, renal and skeletal systems.

The elfin facies syndrome

The elfin facies syndrome is characterized by idiopathic infantile hypercalcemia; mental retardation; cardiovascular anomalies, usually supravalvular aortic stenosis and peripheral pulmonary artery stenosis; a peculiar elfin facies and oral anomalies, primarily enamel hypoplasia and oligodontia. The dental features found in the three cases reported include enamel hypoplasia, severe dental decay, oligodontia, pulp stones, microdontia, and abnormally small roots. Some consistent cephalometric abnormalities were thought to contribute to the unusual facial appearance of these patients.

The Williams elfin facies syndrome. A new perspective

Evaluation of 19 patients with the Williams elfin facies syndrome, in order to more completely delineate the total spectrum of the disorder, indicates that "infantile hypercalcemia, peculiar facies, supravalvular aortic stenosis" designation which was heretofore used is inappropriate. Only 32% of the patients have evidence of supravalvular aortic stenosis and not one of them has had documented hypercalcemia, including eight patients who had a serum calcium determination in the first year of life. Rather, the most consistent features are growth deficiency which is predominantly of postnatal onset, mild microcephaly with mental deficiency, and an altered pattern of facial development which includes short palpebral fissures, a stellate pattern in the iris, medial eyebrow flare, a depressed nasal bridge with anteverted nares, and thick lips. The disorder is a sporadic occurrence of unknown etiology.