Osteogenesis imperfecta type II

Alternate names

Osteogenesis imperfecta congenita perinatal lethal form; Osteogenesis imperfecta congenita; Vrolik type of osteogenesis imperfecta; OI type 2; Osteogenesis imperfecta type 2; Perinatally lethal OI; Lethal osteogenesis imperfecta

Definition

Osteogenesis imperfecta type II is a lethal type of osteogenesis imperfecta , a genetic disorder characterized by increased bone fragility, low bone mass and susceptibility to bone fractures. Patients with type II present multiple rib and long bone fractures at birth, marked deformities, broad long bones, low density on skull X-rays, and dark sclera.

Epidemiology

The overall prevalence of OI is estimated at between 1/10,000 and 1/20,000 but the prevalence of type II is unknown.

Types

There are three subtypes of OI type II (A, B and C) that are characterized by different radiological features.

Genetics

• OI type IIA is caused by mutations of the COL1A1 and COL1A2 genes (17q21.31-q22 and 7q22.1 respectively) and transmission is autosomal dominant.
• Type IIB can be autosomal dominant and also caused by mutations of the COL1A1 and COL1A2 genes (17q21.31-q22 and 7q22.1 respectively) or it can be autosomal recessive and caused by mutations in the CRTAP gene (3p22) (sometimes described as OI type VII) or the LEPRE1 gene (1p34) (sometimes described as OI type VIII) or the PPIB gene (15q21-q22) (sometimes described as OI type IX).

Signs and symptoms

• Patients with OI type IIA present with broad ribs with multiple fractures, continuous beaded ribs and severe undermodeling of the femur
• OI type IIB presents with normal or thin ribs with some fractures, discontinuous beaded ribs and some undermodeling of the femur
• OI type IIC presents with varying thickness of the ribs, discontinuous beading of the ribs, malformed scapulae and ischiae, and slender and twisted long bones.
• Type IIC is extremely rare and its existence is even doubted.

Diagnosis

The diagnosis of COL1A1/2-OI is established in a proband by identification of a heterozygous pathogenic or likely pathogenic variant in COL1A1 or COL1A2 by molecular genetic testing.[1].

Treatment

• Ideally, management is by a multidisciplinary team including specialists in medical management of OI, clinical genetics, orthopedics, rehabilitation medicine, pediatric dentistry, otology/otolaryngology, and mental health. [2].
• Bracing of limbs depending on OI severity
• Orthotics to stabilize lax joints
• Physical activity; physical and occupational therapy to maximize bone stability, improve mobility, prevent contractures, prevent head and spine deformity, and improve muscle strengthening
• Mobility devices as needed; and pain management.
• Fractures are treated with: as short a period of immobility as is practical; small and lightweight casts
• Physical therapy as soon as casts are removed; and intramedullary rodding when indicated to provide anatomic positioning of limbs.
• Progressive scoliosis in severe OI may not respond well to conservative or surgical management.
• Bisphosphonates continue to be used most extensively in severely affected children with OI.
• Surgical treatment for basilar impression should be done in a center experienced in the necessary procedures.
• Dental care strives to maintain both primary and permanent dentition, a functional bite or occlusion, optimal gingival health, and overall appearance. Conductive hearing loss may be improved with middle ear surgery; later-onset sensorineural hearing loss is treated in the same manner as when caused by other conditions.
• Mental health support through psychiatry/psychology and appropriate social worker intervention can improve quality of life.

NIH genetic and rare disease info

• NIH info on Osteogenesis imperfecta type II

Osteogenesis imperfecta type II is a rare disease.

Osteogenesis imperfecta type II Resources
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