The main character of the novel Freak the Mighty, Kevin (aka Freak), suffers from the rare birth defect known as Morquio (or Morquio's) syndrome. It is also referred to as mucopolysaccharidosis IV. Kevin suffered from virtually all of the major symptoms, including dwarfism; heart problems (including enlarged and abnormal development); restricted skeletal development; and spinal cord compression. Other symptoms include large fingers, knock-knees, abnormally spaced teeth, joint problems, and flared ribs. At birth, children with Morquio's seem normal, and the abnormalities only begin to appear at the age of two or three. There are two forms: Type A and Type B. The disease was diagnosed by the Uruguayan Luis Morquio in 1929.
Kevin’s actual medical diagnosis in Freak the Mighty is morquio syndrome. This is a recessive genetic disease whereby the body lacks or has an insufficient quantity of the substance that is required for the breakdown of glycosaminoglycans. A progressive accumulation of glycosaminoglycans to a certain level causes organ damage. Kevin displayed a number of the syndrome’s symptoms including dwarfism. He is described as being about only three feet tall, a height way below par for an eighth grader. This is in addition to an abnormal skeleton development and hyper mobile joints that render him immobile by way of legs causing him to use crutches as a walking aide and also have leg braces. In addition to that, Kevin experienced scoliosis, a bending of the spinal cord that caused him to have a twisted body. This syndrome basically results in internal body organs to develop much faster than the body itself leading to life threatening consequences. In Kevin’s case, the heart grew faster than the body and this led to his demise.
Freak suffers from the disease known as Morquio Syndrome, which affects his metabolism. The disease presents when the body is missing or doesn't have enough of a substance needed to break down long chains of sugar molecules called glycosaminoglycans (formerly called mucopolysaccharides). There are many major symptoms (as seen above), including dwarfism and heart problems, etc. In layman’s terms, he grows faster on the inside than he does on the outside.