AP2S1 and Cognitive impairment: Patients with FHH3 usually show significantly higher serum calcium and magnesium, higher PTH levels, and lower urinary calcium excretion, and more obvious clinical symptoms, which can be combined with cognitive impairment and psychomotor dysplasia.[5,7] The clinical manifestations of the proband in this study were more similar to FHH3, but no mutations in GNA11 and AP2S1 genes were detected.