What could happen if a person doesn't get the proper amount of protein in his or her diet?

Early signs are loss of muscle mass, oedema, problems with keratinous area e.g. skin, hair, nails. The longer-term result is kwashiorkor for which the classic sign, particularly in children, is a bloated abdomen.

Explanation:

Without adequate protein intake, the body begins to conserve energy and redirects protein from muscle to other higher priority needs, such as maintaining basal metabolism. One of the signs is oedema, the retention of fluid due to decreased serum albumin levels. Keratin is a protein found in skin, hair and nails and hair loss can also occur. The long-term result is called kwashiorkor, when the symptoms become severe, such as fluid retention giving the classic picture in children of an emaciated child with a bloated abdomen.

If protein deficiency is concurrent with energy deficiency, a condition called marasmus occurs, in which muscle wasting and severe weakness result from using protein as sn energy source.

that is wrong, its not thymus.