This pt has osteomalacia / rickets (since he's a kiddo). Caused by defective mineralization of osteoid (osteomalacia) or cartilaginous growth plates (rickets, only in children).
Most commonly d/t Vitamin D deficiency.
Children with rickets have pathologic bow legs (genu varum), bead-like costochondral junctions (rachitic rosary), craniotabes (soft skull).
Dec. Vitamin D (normal function is to reabsorb Ca2+ and PO4)
Dec. serum Ca2+
Dec. serum PO4