Genetic Regulation of Parathyroid Gland Development
Apart from the anomalies of the parathyorid gland development, hypoparathyroidism may occur in association with other developmental anomalies involving dysmorphic features, sensorineural deafness, lymphedema, nephropathy, and cortical thickening of tubular bones. This chapter focuses on those forms of hypoparathyroidism that are often present in early life, as these are likely to be associated with parathyroid gland agenesis or hypoplasia, or a congenital deficiency of parathyroid hormone (PTH), or an early destruction of the parathyroids. The hypoparathyroidism in these forms is characterized by hypocalcemia and hyperphosphatemia due to a deficiency in PTH secretion. The congenital developmental anomalies associated with hypoparathyroidism include the DiGeorge, HDR (hypoparathyroidism, deafness, and renal anomalies), Kenney-Caffey, and Barakat syndromes, and also syndromes associated with either lymphedema or dysmorphic features and growth failure. Patients with DiGeorge syndrome (DGS) typically suffer from hypoparathyroidism, immunodeficiency, congenital heart defects, and deformities of the ear, nose, and mouth. hypoparathyroidism, deafness, and renal anomalies syndrome includes hypoparathyroidism, deafness, and growth and mental retardation. Kenny-Caffey syndrome, which is associated with short stature, is characterized by osteosclerosis and cortical thickening of the long bones, delayed closure of the anterior fontanel, basal ganglia calcification, nanophthalmos, and hyperopia. Additional familial syndromes in which hypoparathyroidism is a component include: mitochondrial disorder and pluriglandular autoimmune hypoparathyroidism. The study concludes by stating that much remains to be established regarding issues of phenotypic variance and interspecies differences. © 2008 Elsevier Inc. All rights reserved.