ATLL cells express factors such as interleukin-1, tumor necrosis factor β, parathyroid hormone-related protein (PTHrP), macrophage inflammatory protein-1α (MIP-1α) and receptor activator of nuclear factor-κB ligand (RANKL) that directly and/or indirectly stimulate osteoclast differentiation and activity, resulting in hypercalcemia [20-24]. The gene discussed is PTHLH; the disease is Hypercalcemia.