ESPE Abstracts

McCune-Albright syndrome (MAS) is a rare genetic disorder caused by somatic activating mutations in the GNAS gene. Depending on the embryonic stages at which the mutation occurs, the phenotype of MAS may vary widely. Typical features include polyostotic fibrous dysplasia, café-au-lait skin lesions and multiple endocrinopathies, most frequently a peripheral precocious puberty. More rarely, patients have a liver involvement. We report the case of a 2 years-old boy with a newly diagnosed MAS who presented initially with a severe neonatal cholestasis. Shortly after birth, the patient developed jaundice, pale stools and hepatomegaly. Laboratory tests revealed conjugated hyperbilirubinemia, mildly elevated transminases levels and an important increase of the gamma-glutamyl-transferase. Liver ultrasound did show neither extrahepatic bile duct nor liver abnormalities. A liver biopsy revealed an intrahepatic bile duct paucity which led to the initial suspicion of an Alagille. Cholestasis and metabolic diseases gene panels and a whole exome sequencing on peripheral blood were non contributive. The cholestatic disease moderately improved over the first 2 years under treatment with ursodeoxycholic acid, fat-soluble vitamins and diet, but still persist. At the age of 2 years and half, the patient was presented to our endocrinology unit for his retarded growth. The physical examination revealed two café-au-lait macules on the left leg, a painless limping and a difference in his leg lengths. Lower limbs X-ray showed multiple heterogeneous osteolytic lesions, compatible with fibrous dysplasia, involving the left iliac wing, the left femoral neck and diaphysis and the left tibial diaphysis. The bone lesion in the left femoral neck caused a coxa vara hip deformity and a fissuration of the cortical bone. Bone scintigraphy reinforced the suspicion of fibrous dysplasia and showed additional lesions in the left humerus, the left maxillary bone and the right frontal bone. The patient underwent a growth friendly osteosynthesis of the left femur to correct the coxa vara deformity and to prevent further fractures. A bone biopsy confirmed the diagnosis of polyostotic fibrous dysplasia. The result of GNAS gene analysis in the bone tissue is pending. This case highlights the importance of considering MAS as one differential diagnosis in neonatal cholestasis. An exclusion of a GNAS mutation in peripheral blood does not exclude a MAS. An early diagnosis of MAS allows a screening for potentially associated endocrinopathies.