Ohioan Gyattism Disorder

Ohioan Gyattism Disorder (OGD) is a disorder affecting the muscles in the lower back, thigh and in severe cases, the head and neck. The first recorded case was in 1962 in Akron, Ohio affecting a 15-year-old boy "Mat Smith"
Symptoms include:

Pain and discomfort in the lower back, thigh, "behind" and neck.
As the disorder progresses it results in extreme back pain causing the patient to arch their back - thus promoting the progression of "Scoliosis"

At the end of its progression, the disorder causes the "Behind" of the patient to be inflamed, the inflammation can increase the behind's thickness to increase by 3-5 cm.

Person 1: Hey what happened to Mat?
Person 2: You didn't hear? He has OGD.
Person 1: Oh my god, my grandfather has Ohioan Gyattism Disorder!