Unequal leg length (also termed leg length inequality, LLI or leg length discrepancy, LLD) is where the legs are either different lengths or appear to be different lengths because of misalignment. The condition has been estimated to affect between 40% and 70% of the population, with at least 0.1% having a difference greater than 20 mm (0.79 in). Classification
There are two main types of leg length inequalities:

Structural differences are caused by the legs themselves being measurably different in length, usually due to differences in the length of the femur in the thigh or the tibia and fibula bones in the lower leg. This may be a birth defect or it may occur after a broken leg, serious infection, or local damage to one of the growth plates in a leg. The other, more common, type is seen when the legs themselves are the same length, but due to neuromuscular injuries in the pelvis or upper leg, one leg or hip is held higher and tighter than the other (hypertonicity in the musculature of the pelvis or leg). These unequally tightened muscles cause the legs to seem to be different lengths, even though careful measurement would show equal lengths of the actual leg. This is called leg length alignment asymmetry (LLAA) and can be seen while lying down. Diagnosis and workup
Unequal leg length in children is frequently first suspected by parents noticing a limp that appears to be getting worse.
Supravalvular aortic stenosis is a congenital obstructive narrowing of the aorta just above the aortic valve and is the least common type of aortic stenosis. It is often associated with other cardiovascular anomalies and is one of the characteristic findings of Williams syndrome. The diagnosis can be made by echocardiography or MRI. Genetics
Supravalvular aortic stenosis is associated with genetic damage at the Elastin gene locus on chromosome 7q11.23. Fluorescent in situ hybridisation techniques have revealed that 96% of patients with Williams syndrome, where supravalvular aortic stenosis is characteristic, have a hemizygous deletion of the Elastin gene. Further studies have shown that patients with less extensive deletions featuring the Elastin gene also tend to develop supravalvular aortic stenosis

Pathophysiology
Supravalvular aortic stenosis is due to diffuse or discrete narrowing of ascending aorta. The murmur associated with it is systolic murmur and is similar in character to valvular aortic stenosis murmur but commonly present at 1st Intercostal space (ICS) on the right. Individuals with this anomaly may have unequal carotid pulses, differential blood pressure in upper extremities and a palpable thrill in Suprasternal notch. Individuals with significant supravalvular AS chronically may develop left ventricular hypertrophy and also are at risk of developing coronary artery stenosis. With increased metabolic demands (e.g. exercise) such individuals may develop subendocardial or myocardial ischemia due to increased myocardial oxygen demand and seek medical help with symptoms of exercise induced angina. Diagnosis
Treatment


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