The activation mutation of Gsα subunit appears in three distinctive clinical patterns: single bone involvement (monostotic form), which is the most common presentation (70% of patients); multiple bone involvement (polyostotic form), a less common form (30%); and McCune-Albright syndrome, a rare variant of the polyostotic form with pigmentation and one or multiple endocrine hyper functions. We report here two cases of Gsα subunit mutation. One of the cases was polyostotic fibrous dysplasia in a five-year-old boy and the other case was McCune-Albright syndrome presented with combined precocious puberty. Treatment of the polyostotic fibrous dysplasia was unsuccessful; however, the combined precocious puberty was treated successfully. We conclude that the progression and response to treatment of bone fibrous dysplasia is age-dependent. This conclusion is based on the many studies that have reported clinical and radiological improvement in bone fibrous dysplasia with pamidronate treatment in adult patients; however, the same successful results were not achieved in childhood.

Keywords: Gsα altyapısı, mutasyon, polrostatik fibroz displazi, McCune, Albright sendromu.