Osteogenesis Imperfecta—A Human Temporal Bone Case Study

Abstract

Osteogenesis imperfecta (OI) is defined as one of the inherited connective tissue disorders that can result in fragile bones, blue sclera, and deafness. This genetic disease affects collagen type 1 (COL1), which leads to different manifestations depending on the mutation. There are four subtypes of OI, based on different defects in the collagen synthesis, types I, II, III, and IV. OI type I, previously known as OI tarda, is the most common and least severe subtype, is autosomal dominant, and results in blue sclera, increased risk of bone fracture and progressive hearing loss in 50% of patients. OI type II, previously known as OI congenital, is the most severe form, it usually leads to perinatal death and is autosomal recessive. OI Type III is the most severe type among children who survive the neonatal period. The degree of bone fragility and the fracture rate vary widely. OI Type IV diagnosis often occurs later in life and usually represents the patients that do not fit into subtypes I–III (1,2). Deafness is one of the main features of osteogenesis imperfecta and conductive hearing loss is the most common form, but mixed or pure sensorineural hearing losses are not uncommon (3). In the University of Minnesota temporal bone collection, we found one case that fits in the OI diagnosis.