Dictionary

Lou Gehrig’s disease See amyotrophic lateral sclerosis.

lordosis Inward curvature of the spine. The spine is not supposed to be absolutely straight, so some degree of curvature is normal. When the curve exceeds the usual range, it may be due to musculoskeletal disease or simply to poor posture. Treatment usually involves physical therapy, although in severe cases surgery, casting, and/or bracing may…

longitudinal study A study done over the passage of time. For example, a longitudinal study of children with Down syndrome might involve the study of 100 children with this condition from birth to 10 years of age. Longitudinal study is the opposite of cross-sectional (synchronic) study. Also known as diachronic study.

longitudinal section A section that is cut along the long axis of a structure. Longitudinal section is the opposite of cross-section.

longitudinal Along the length of something; running lengthwise or, by extension, over the course of time.

longevity Lifespan. Increased longevity means a longer life.

long-chain-3-hydroxyacyl-CoA dehydrogenease deficiency See deficiency, LCHAD.

long QT syndrome A disorder of the heart’s electrical system that predisposes individuals to irregular heartbeats, fainting spells, and sudden death. The irregular heartbeats are typically brought on by stress or vigorous activity. Abbreviated LQTS. LQTS is often symptomless and undiagnosed, but it is well known as a cause of sudden cardiac death in young,…

loin The portion of the lower back from just below the ribs to the pelvis.

Loeys-Dietz syndrome An inherited syndrome characterized by aortic aneurysms and other blood vessel abnormalities in children. The condition is often associated with other birth defects. The aortic aneurysms of Loeys-Dietz syndrome are prone to rupture at a smaller size than other aneurysms, with early identification of the condition and surgical intervention critical for survival.

locus In genetics, the place a gene occupies on a chromosome. The plural is loci.

locomotive system The bones, the joints, and the muscles that contract and relax to move the joints and bones.