GNAS and pseudohypoparathyroidism type 1B: For example, in establishing the diagnosis of pseudohypoparathyroidism type 1b (PHP1b), methylation‐specific MLPA (MS‐MLPA) may be employed to detect genetic (e.g. deletions) or epigenetic (e.g. altered patterns of methylation) abnormalities within the differentially methylated regions (DMRs) of the GNAS locus, although alternate methods such as CpG bisulphite pyrosequencing are frequently used to confirm the presence of specific methylation defects 79.