In the rare cases of infants who survive their first year of life, severe developmental and motor delays are seen; neither of two infants studied in 2019, both aged around two years, had achieved head control, and both required a ventilator to breathe.Type II is also known as the "lethal perinatal" form of OI, and is not compatible with survival into adulthood. Due to similarly severely deformed bones, sometimes infants with severe type III are wrongly initially classified as type II; once long-term survival is shown, they are considered as having type III instead. : 1511

Type III
Collagen quantity is sufficient, but is not of a high enough quality. : 1512  Clinical differentiation between types III and IV is not always simple, and is further confounded by the fact that an untreated adult with type IV may have worse symptoms than a treated adult with type III;: 1511  features only found in type III are its progressively deforming nature: 1511–1512  and the presence of a face with a "triangular" appearance.
: 161  The Norse king Ivar the Boneless, who lived c. 800 CE, is speculated to have had OI as well.Nicolas de Malebranche is oft credited as being the first person to describe the physical characteristics of OI in his 1688 book The Search after Truth, in which he describes a man who has had his "bones broken in the places a murderers would be" all his life. His confident description of the pathology of the disorder, however, which creates what he termed «enfants monstrueux» ("monstrous children"), is scientifically void—he wrote that it was due to the mothers antepartum viewership of a public execution by breaking wheel. : 683 : 165–168 The earliest modern scientific studies of OI began in 1788 by Olof Jakob Ekman, who described the condition, which he termed "osteomalacia congenital", in his doctoral thesis and mentioned cases of it going back to 1678, all in the same family, through three generations. Ekmans description of the condition mentioned dwarfism, bone fragility, and bowing of the long bones. : 763  In 1831, Edmund Axmann gave a detailed description of it in himself and his two brothers, being the first to mention blue sclerae as a characteristic sign of OI. : 683  Jean Lobstein first described the mild form of the condition, today known as type I, in 1833, calling it "osteopsathyrosis idiopathica". : 347 It was not until 1912 that hearing loss was positively recognized as a symptom of OI, first mentioned in a brief paper by the English physician Charles Allen Adair-Dighton.