Fig. 4.

Gender and age distribution. A The gender distribution of the muscle expansion type and fat hyperplasia type. As the graph shows that there were 20 cases of muscle expansion type, and the male-to-female ratio was 1:1. There were 14 cases of fat hyperplasia type, and the male-to-female ratio was 1:2.5. B The age distribution of all cases. As the graph shows that the age distribution was 20–30 years old in 12 cases, 31–40 years old in 6 cases, 41–50 years old in 9 cases, and 51–60 years old in 7 cases