RESUMO
Pseudohypoparathyroidism Ia (PHP-Ia) results from a specific deficiency of the alpha subunit of stimulatory G protein, manifested by resistance to parathormone and a characteristic phenotype, referred to as Albright hereditary osteodystrophy (AHO). Several mutations were identified in the GNAS1 gene in individuals with PHP-Ia and pseudopseudohypoparathyroidism (PPHP). A single GNAS1 mutation may be responsible for both PHP-Ia e PPHP in the same family, when inherited from the maternal and the paternal allele, respectively. The authors present the case of a teenage boy with PHP- Ia. The study revealed the GNAS1 mutation c.899A >T (p.Lys300Ile) in exon 11. After the genetic study of his parents, we have identified the same mutation in the mother, who had only somatic alterations (AHO), not associated with hormone resistance (PPHP). This is an original mutation, not yet described in the literature.