Hypercalciuria, Absorptive, 1

For a phenotypic description and a discussion of genetic heterogeneity of absorptive hypercalciuria, see 143870.

Imamura et al. (1998) reported the cases of 2 unrelated girls with multiple malformations, each of whom had an unbalanced translocation chromosome with deletion of the 4q33-qter segment and addition of a segment from another unidentified chromosome. One of the 2 girls had asymptomatic kidney stones. Both had excess urinary calcium excretion, exaggerated excretion on oral calcium load, and reduced but excessive excretion on restricted calcium intake. The urinary calcium excretion of their parents was normal. Both girls were thus diagnosed to have sporadic absorptive hypercalciuria. Imamura et al. (1998) suggested that the 4q33-qter segment contains the putative gene for absorptive hypercalciuria.

Townes et al. (1979) recognized deletion of the terminal region of the long arm of chromosome 4 as a distinct syndrome. The syndrome comprises minor facial anomalies, cleft palate, limb and digital abnormalities (especially of the fifth finger), congenital heart defects, postnatal growth deficiency, and developmental delay. Giuffre et al. (2004) described a newborn girl with a de novo terminal 4q deletion (4q31.3-qter) and a characteristic phenotype of minor facial anomalies, cleft palate, congenital heart defect, abnormalities of hands and feet, and postnatal growth deficiency. Excessive urinary calcium excretion on standard milk formula and on oral calcium load was found. At 2 months of age, ultrasound showed kidney calcifications. Clinical and laboratory data supported the diagnosis of absorptive hypercalciuria or abnormal regulation of calcium-sensing receptors in the renal tubules. The findings supported the hypothesis that a putative gene for hypercalciuria is located on the terminal segment of 4q.