Textbook Problem

Osteogenesis imperfecta (OI) is a genetic disorder caused by a mutation in a gene for collagen. As bones develop, collagen forms a scaffold for deposition of mineralized bone tissue. In children with OI, the scaffold forms improperly, causing them to be born with multiple fractures in their fragile bones and to require many corrective surgeries. Table 1 and Table 2 show the results of an experimental test of a new drug. Treated children with OI, all less than 2 years old, were compared to similarly affected children of the same age who were not treated with the drug.

TABLE 1 Effect of Drug on Bone Properties in Children with OI

	Vertebral Area, in cm2
Treated Child	(Before Treatment)	(After Treatment)	Fractures Per Year
1	14.7	16.7	1
2	15.5	16.9	1
3	16.7	16.5	6
4	17.3	11.8	0
5	13.6	14.6	6
6	19.3	15.6	1
7	15.3	15.9	0
8	19.9	13.0	4
9	10.5	13.4	4
Mean	11.4	14.9	2.6

TABLE 2 Bone Properties in Children with OI Who Received No Drug Treatment

	Vertebral Area, in cm2
Control Child	(Initial)	(Final)	Fractures Per Year
1	18.2	13.7	4
2	16.5	12.9	7
3	16.4	11.3	8
4	13.5	17.7	5
5	16.2	16.1	8
6	18.9	17.0	6
Mean	16.6	13.1	6.3

How many of the untreated children showed an increase?