Features of Turner and Noonan Syndromes may overlap, but there are often features that can help to distinguish the two conditions.
Overlapping features include:
(1) short stature
(2) cardiac abnormalities
(3) webbed neck
(4) renal abnormalities
(5) micrognathia
Features of Turner syndrome:
(1) almost all patients are female
(2) different facial dysmorphism
(3) much lower rate of developmental delay
(4) heart defects are typically left-sided
(5) different pattern of renal involvements
Chromosomal analysis is the definitive test for distinguish the two syndromes.