Isolated Cushing's syndrome: an unusual presentation of McCune-Albright syndrome in the neonatal period.

Cushing's syndrome (CS) may develop at any time in childhood. In the neonatal period, the major cause is the overactivation of adrenal cells within the context of McCune-Albright syndrome (MAS). The hypercorticism usually appears with other clinical signs of MAS. We report here a case of isolated neonatal CS as the initial evidence of MAS. This newborn girl was referred to our pediatric endocrine unit at the age of 3 months for hypotonia and growth retardation. Clinical examination revealed facial plethora, moon face, and swollen limbs. Laboratory data demonstrated ACTH-independent CS. Magnetic resonance imaging showed moderate bilateral adrenal hyperplasia, though more marked in the left adrenal gland, without nodules. This peripheral hypercorticism without well-defined adrenal tumor was suggestive of MAS, although no other signs like precocious puberty or café-au-lait spots were found. An activating Gsalpha gene mutation was found on DNA extracted from blood. Because MAS is a somatic disease, usually with unilateral effects, we tried to remove only the larger adrenal gland, where the mutation was demonstrated. This female newborn later developed the classical triad of MAS, reinforcing this diagnosis. Cushing's syndrome in infants, even when isolated, may suggest a diagnosis of MAS.