Rickets is usually caused by vitamin D deficiency. This is why two sisters at first puzzled their doctors. At ages 7 and 3, the girls clearly suffered from the same disorder. Their too-soft leg bones bowed outwards and the ends were bearing so much strain that their knees protruded, resembling knobs. The girls' rib cages caved in. These were the unmistakable symptoms of rickets, but the children followed a healthy diet.

Even before the skeletal deformities became apparent, all was not right. As infants, the girls' growth lagged. The soft spot on the tops of their skulls did not close and harden by 18 months, as it normally does. This was the first sign of the underlying lack of vitamin D. The sisters' teeth erupted late and were soon lost to decay.

The fact that the girls' parents were blood relatives clued physicians to the possibility of a genetic explanation behind their bone disorder. A second clue came from analyzing the relative amounts of intermediate biochemicals resulting from the girls' cells using vitamin D. The diagnosis; a very rare, inherited form of vitamin D refractory rickets. Even though the girls ate foods rich in vitamin D, received vitamin supplements, and got plenty of sunshine (needed to activate vitamin D precursors in the skin), they were still sick because their bodies could not use the abundant vitamin. Vitamin D entered their cells, but it could not bind to the genetic material, a vital step in controlling production of bone proteins.

Copyright ©1998 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use and Privacy Policy.
McGraw-Hill Higher Education is one of the many fine businesses of The McGraw-Hill Companies.
For further information about this site contact mhhe_webmaster@mcgraw-hill.com.