The Endocrine Chameleon: Expanding the Phenotype of Pseudohypoparathyroidism 1A in Infancy

Pseudohypoparathyroidism 1A (PHP1A) is the best-known representative of inactivating parathyroid hormone (PTH)/PTHrP-signaling disorders (iPPSD). The associated phenotype develops over time and often includes hormonal resistances, short stature, and osteoma cutis. More complex and very early manifestations have also been reported. Neonatal complications may indicate a more severe course of the disease. Here, we report 3 patients with heterozygous GNAS variants and infancy onset of iPPSD2/PHP1A.

Patient 1 is a 15-month-old boy who presented with severe chronic noninfectious diarrhea and elevated thyroid-stimulating hormone (TSH) beginning at 1 month of age, leading to life-threatening failure to thrive. Patient 2 is a 4-year-old boy with a history of bronchopulmonary dysplasia as well as neonatal-onset severe pulmonary complications, including critical pulmonary bleeding and recurring pulmonary infections and TSH elevation. Patient 3 is a 4-year-old girl who exhibited signs of PTH resistance and progressive osteoma cutis at the age of 1-2 weeks and obesity at the age of 3 months.

The phenotypic spectrum of iPPSD2/PHP1A in neonates and infants may include severe gastrointestinal, pulmonary, and endocrine manifestations, which may delay diagnosis if not recognized as a spectrum disorder of G_sα deficiency. The cases support the hypothesis that early-life manifestations may indicate a more complicated course of the disease. Elevated PTH or TSH in infants with unclear symptoms or conditions should prompt evaluation for disorders of the iPPSD spectrum. In the absence of reliable predictors for the individual courses of PHP1A, in-depth clinical screening for possible manifestations beyond the classical spectrum is warranted even in infancy.