While he was short, he actually had exceptionally large feet for his height, with his shoes measuring in at a European size of 43 at the age of 18 (US size 10). According to Rainier, by the time he hit 21, while he still barely classified as a dwarf in height, his shoe size had gone up to a European size 53 (US 20).
Although his feet were continuing to grow at a remarkable pace, Rainer himself was staying at more or less the same height. That's when something even more bizarre than his clown-feet happened. For an unknown reason at the time, Adam started growing again... rapidly. From his 21st birthday to his 32nd, Rainer grew from just under 4 feet 10 inches tall to 7 feet 2 inches tall (1.47 m to 2.18 m).
After a medical exam, Doctors F. Windholz and A. Mandl discovered a tumor on his pituitary gland, which not only explained his rapid growth but his partial blindness, as well. This tumor resulted in a condition known as acromegaly, where the pituitary gland produces excessive amounts of growth hormone during adulthood. In 1930, doctors tried to fix the problem by removing the tumor, but he still continued to grow, albeit at a much slower rate.
Over the final 19 years of his life, Rainer's spinal curve would continue to increase and he'd grow another 6 inches. In 1950, he died at the age of 51 at a height of about 7 feet 8 inches (2.34 m), making him the only known person to spend time officially classified as a dwarf and a giant.