Pseudohypoparathyroidism.

Area of Science:

• Endocrinology
• Genetics
• Rare Diseases

Background:

• Pseudohypoparathyroidism (PHP) is a group of rare disorders affecting mineral metabolism, characterized by resistance to parathyroid hormone (PTH).
• Phenotypes like Albright hereditary osteodystrophy (AHO) and progressive osseous heteroplasia are linked to hormonal resistance, often stemming from alterations in the GNAS locus.
• Overlapping phenotypes and genetically distinct disorders mimicking AHO necessitate a revised classification.

Purpose of the Study:

• To introduce and advocate for the broader term "inactivating PTH/PTHrP signaling disorder (iPPSD)" to encompass PHP and related conditions.
• To emphasize the importance of genetic and epigenetic analyses for differentiating forms of iPPSD for tailored treatment and counseling.
• To refine the classification of rare disorders involving impaired PTH/PTHrP cAMP signaling.

Main Methods:

• Review of clinical phenotypes, genetic/epigenetic alterations in the GNAS locus, and PTH resistance.
• Analysis of diagnostic criteria for PHP and related disorders.
• Comparison with newly characterized non-GNAS dependent disorders mimicking AHO.

Main Results:

• The term PHP is considered obsolete due to overlapping phenotypes and the existence of non-GNAS dependent disorders.
• A new classification proposes "inactivating PTH/PTHrP signaling disorder (iPPSD)" for all congenital rare disorders of the PTH/PTHrP cAMP pathway.
• Genetic and epigenetic analyses are crucial for differentiating iPPSD subtypes, guiding therapeutic planning and patient management.

Conclusions:

• The term "inactivating PTH/PTHrP signaling disorder (iPPSD)" offers a more comprehensive and accurate classification for these rare conditions.
• Accurate diagnosis and differentiation of iPPSD subtypes are essential for effective patient care, including counseling and follow-up.
• Understanding the genetic basis of these disorders is key to advancing therapeutic strategies.