Hypercalcemia is seen in-
People with Williams syndrome (also known as Williams Beuren syndrome or WS) may have problems handling calcium. Most children with WS have blood levels of calcium that are in the high normal range with a smaller fraction of affected individuals (around 15 percent) having very high levels of calcium (hypercalcemia) Ref Davidson 23ed pg 371
Renal osteodystrophy
Vit D resistant rickets
Hypoparathyroidism
Williams syndrome
Fluid and electrolytes