We report on a 17-year-old male with severe pre- and postnatal growth retardation, craniosynostosis, distinctive facial features, acanthosis nigricans, deafness, mental retardation and progressive multi-organ involvement, particularly of the endocrine system, including hypothyroidism, hypogonadism, transitory hypoparathyroidism, and insulin resistance. In order to find a common mechanism explaining these multiple abnormalities, we searched for a possible defect in the signal transduction pathways from membrane to nucleus involving G-protein coupled receptors (GPCR). Adenylyl cyclase activity was evaluated by assaying c-AMP in the patient's cultured fibroblasts stimulated with several drugs and toxins acting on different effectors upstream of adenylyl cyclase. The preliminary results indicate a reduced cAMP accumulation in the patient, neither caused by constitutive activation of Gi nor inhibition of Gs signaling, and probably resulting from an alteration in the adenylyl cyclase system. The differential diagnosis with syndromes showing common clinical features with our patient is discussed.