Dear EditorLuo et al. 1 reported two cases of autosomal
dominant pseudohypoparathyroidism type 1B (AD-PHP1B) and reviewed literature about
the genetic and epigenetic characteristics of AD-PHP1B. Pseudohypoparathyroidism
(PHP) is a cluster of heterogeneous diseases characterized by hypocalcemia and
hyperphosphatemia due to resistance to parathyroid hormone (PTH). PHP1B almost
results from methylation abnormalities of the maternal differentially methylated
regions (DMRs) and can be divided into sporadic PHP1B and AD-PHP1B 1. As mentioned in this article 1, AD-PHP1B is caused by heterozygous maternal
deletions within GNAS or STX16, which are associated with loss of methylation at the
A/B DMR alone or at all maternally methylated GNAS exons. While sporadic
PHP1B remains unclear at the molecular level, except for approximately 10%
of the patients caused by paternal uniparental isodisomy or heterodisomy involving
chromosome 20q (patUPD20q) 2. Here, we would
like to present a rare case of sporadic PHP1B occurring in association with
hypokalemia.
A rare case of uniparental isodisomy of chromosome 19 with no phenotypic abnormalities