Deletion of chromosome 22q11 and pseudohypoparathyroidism.
A newborn boy with complex congenital heart disease, unilateral renal agenesis, and hypocalcemia was found to have a submicroscopic deletion of 22q11.2 (DiGeorge anomaly). In evaluating the pathogenesis of the hypocalcemia, repeatedly elevated or normal levels of parathyroid hormone were found, consistent with a diagnosis of pseudohypoparathyroidism. Pseudohypoparathyroidism can be due to mutation of a GTP binding protein (Gs-alpha protein) located on chromosome 20. Since there is another G protein locus (Gz alpha) adjacent to the DiGeorge critical region of chromosome 22, we hypothesized that a more extensive deletion may lead to pseudohypoparathyroidism. Fluorescence in situ hybridization was performed using a probe containing the Gz alpha gene, but no deletion was detected. This patient emphasizes the importance of determining the pathogenesis of the hypocalcemia in cases of DiGeorge anomaly.
Craigen
W J
WJ
Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA. wcraigen@bcm.tmc.edu
Lindsay
E A
EA
Bricker
J T
JT
Hawkins
E P
EP
Baldini
A
A
D002872:Chromosome Deletion; D002892:Chromosomes, Human, Pair 22 / Q000235:genetics*; D004062:DiGeorge Syndrome / Q000235:genetics; D006801:Humans; D006996:Hypocalcemia / Q000235:genetics; D007231:Infant, Newborn; D008297:Male; D011547:Pseudohypoparathyroidism / Q000235:genetics*