Rickets is a type of vitamin D deficiency disease, primarily caused by insufficient vitamin D in infants, children, or adolescents, leading to disorders in calcium and phosphorus metabolism. It is a chronic nutritional disease characterized by skeletal lesions, mainly manifesting as changes in the fastest growing parts of the skeleton, such as square skull, pigeon chest, funnel chest, bow legs, and knock knees, among other symptoms. On the other hand, tetany is primarily due to hypocalcemia and its manifestations differ; it does not exhibit the skeletal changes seen in rickets but primarily presents as spasms or cramps in the hands and feet. Thus, this constitutes their fundamental difference.