Osteogenesis imperfecta (brittle bone disease)

What it is

Osteogenesis imperfecta, more commonly known as brittle bone disease, is a congenital group of disorders of collagen metabolism that gives brittle weak bones, with bone fragility and fractures. There is a decrease in the amount of normal type I collagen, from a COL1A1 gene mutation. Inheritance is AD for types I to IV, with rare AR types, and most are AD and de novo. Type 1 is the most common and the mildest; type 2 carries a poor prognosis; type 3 goes with hydrocephalus; and type 4 has normal sclera, with tibial bowing as its hallmark.

How it presents

It presents in childhood, and the manifestations are grouped this way:

• Bone: fractures following minor trauma, bone deformity, short stature, scoliosis, coxa vara, codfish vertebrae, flared metaphysis, wormian skull bones along the cranial sutures, basilar invagination, olecranon apophyseal avulsion fracture, congenital anterolateral radial head dislocations, hypotonia, and loose hyperextensible joints with ligamentous laxity.
• Eye: blue sclera, from thin connective tissue.
• Ear: hearing loss, and deafness secondary to otosclerosis.
• Teeth: brownish opalescent teeth, that is dentinogenesis imperfecta, and fragile teeth.
• Vessels: dissection.
• Other: easy bruising, thin skin prone to subcutaneous hemorrhage, hypermetabolism with increased risk of malignant hyperthermia, and MR and AR on the cardiovascular side.

A child brought in with bowing of the legs raises it as well.