Case of the Month #171: Osteogenesis Imperfecta of the Temporal Bone

• Published in: Canadian Association of Radiologists journal 2011-11, Vol.62 (4), p.296-298
• Main Authors: Fuller, Elisa, BSc, Lin, Vincent, MD, FRCSC, Bell, Mary, MD, FRCPC, Bharatha, Aditya, MD, Yeung, Robert, MD, FRCPC, Aviv, Richard I., MBChB, FRCR, Symons, Sean P., MPH, MD, FRCPC
• Format: Article
• Language: English
• Subjects: Adult; Bone diseases; Bones; Diagnosis, Differential; Genetic disorders; Hearing loss; Humans; Male; Medical diagnosis; Medical treatment; Osteogenesis imperfecta; Osteogenesis Imperfecta - diagnostic imaging; Radiology; Temporal bone; Temporal Bone - diagnostic imaging; Tomography; Tomography, X-Ray Computed
• ISSN: 0846-5371; 1488-2361
• DOI: 10.1016/j.carj.2010.04.002

OI is a genetic disease that affects collagen type I (COLI), which leads to a range of manifestations dependent on the mutation. The classic syndrome is progressive hearing loss, blue sclera, and bone fragility. COLI is composed of 2 alpha1 chains and 1 alpha-2 chain, in which each third residue is a glycine amino acid, and elucidates the formation of the triple helical structure [I]. OI results from mutations in the COLlAl or COLI A2 genes responsible for encoding the alpha chains. Dependent on the mutation, different phenotypes result and create subtypes I-IV [2-4]. Recently, additional mutations were discovered in proteins associated with the structural formation of COLI, which led to identification of subtypes V-VlI [5]. OI type I is most common and is the least-severe subtype [5,6]. It results from a frame shift mutation, premature stop codon, or splice site mutation in COLlAl or COL1A2, which leads to decreased production of normal COLI [3]. OI type I is autosomal dominant and results in blue sclera, increased risk of bone fractures, and progressive hearing loss in the second or third decade of life. There may be dentinogenesis imperfecta. Patients are of normal height, with no bone deformities [5]. OI type II is the most severe form and usually leads to perinatal death. It results from mutations in the glycine residue of the alpha chains, greatly disrupting the structural stability of COLI . It is autosomal recessive and presents with multiple bone fractures and deformities at birth, particularly rib fractures that can have respiratory effects. Babies may or may not present with blue sclera [5,6]. OI type III is the most-severe subtype in those babies who survive the neonatal period. It also is caused by a glycine residue mutation, which leads to severe bone deformities, short stature, high bone fragility, and possibly blue sclera, although this fades with age. These patients are often wheelchair bound and may have respiratory difficulties [6]. OI type IV is of intermediate severity and usually represents the cohort of patients that do not fit into subtypes I-III [6]. OI type V is autosomal dominant, seen in 4%- 5% of patients with OL It shows no dentinogenesis imperfecta or blue sclera but is characterized by bone fragility and hypertrophie callous formation [5-7]. Type VI also shows no blue sclera or dentinogenesis imperfecta but presents with bone fragility and deformity. It is autosomal recessive, with negative screening results in assays for CO