Scoliosis even when untreated, with mortality rates similar to the general population. Older beliefs that untreated idiopathic scoliosis necessarily progresses into severe (cardiopulmonary) disability by old age have been refuted by later studies. The many causes of scoliosis include spinal deformities, neuromuscular problems, and inherited diseases or conditions caused by the environment. An estimated 65% of scoliosis cases are idiopathic, about 15% are congenital, and about 10% are secondary to a neuromuscular disease. Idiopathic scoliosis represents a majority of cases, but its causes are largely unknown. Recent studies indicate potential heritability of the disorder. About 38% of variance in scoliosis risk
Supernumerary body part Supernumerary body part Supernumerary body parts are most commonly a congenital disorder involving the growth of an additional part of the body and a deviation from the body plan. Body parts may be easily visible or hidden away, such as internal organs. Many additional body parts form by the same process as conjoined twins: the zygote begins to split but fails to completely separate. This condition may also be a symptom of repeated occurrences of continuous inbreeding in a genetic line. Specific types of additional body parts include: Vestigial structures are anatomical structures of organisms in a species which are