Findings:

A. Initial radiograph from this three-week-old child demonstrates the findings of diffuse osteoporosis, and healing oblique fractures of the femoral diaphyses. Bowing deformities of the markedly foreshortened femora, tibiae, and fibulae can be observed.

B. Subsequent examination obtained seven months later describes advanced healing of the previously demonstrated femoral fractures. Gradually increasing lower extremity weight bearing by the patient has resulted in progressive bowing deformity of the osteoporotic long bones.

C. Examination of the right lower extremity obtained six days after "B" demonstrates a new oblique fracture of the right femoral diaphysis.

Diagnosis:Osteogenesis Imperfecta

Discussion: OSTEOGENESIS IMPERFECTA is a relatively common heterogeneous disorder characterized and sub-classified by age of onset and clinical course, and by the presence/absence of: 1)dentinogenesis imperfecta; 2) blue sclerae; and 3) hearing impairment. Sub-classifications (Types I-IV) are also defined, in part, by inheritance pattern and salient radiographic features.

The principal biochemical defects related to osteogenesis imperfecta (OI) result in the impairment of early stages in the synthesis of connective tissue fibers, as well as faulty cross- linking of the resultant fibers into adult Type I collagen.

Skeletal abnormalities result from congenital osteoporosis (i.e., fragile cortical and trabecular bone), resulting in gross pathological fractures with minimal trauma, and bowing deformities secondary to repeated microscopic fractures.

"Blue" sclerae may be noted by the visualization of the densely vascular choroid through the abnormally thin, translucent scleral layers. This entity may also be described in Ehlers- Danlos Syndrome, in myasthenia gravis, with iron-deficiency anemia, and with protracted corticosteroid therapy.

Dentinogenesis imperfecta, also known as "hereditary opalescent dentin", results from disordered arrangement of tubulin and poor calcification of dentin. An opalescent, amber appearance is cast to the teeth, which are characteristically small and deformed. The roots of the teeth are thin, short, and pointed. Roentgenographically, the teeth demonstrate variable obliteration of the pulp chambers and root canals, and the crumbling and loss of enamel.

"Presenile" hearing impairment is believed to be secondary to otosclerosis.

A. Osteogenesis imperfecta Type 1 aka, Osteogenesis imperfecta tarda, Osteopsathyrosis,
Lobstein Disease, Van der Hoeve Disease)

characteristic features: blue sclerae; autosomal dominant inheritance pattern;
hearing impairment in 30-50% (manifest in 2nd decade); rel. normal birth
weight/length; "triangular" facial appearance (30%).

*multiple fractures are usually present at birth, and accumulate with increasing
frequency during childhood; the result is a characteristic bowing deformity of long bones.

*kyphosis and scoliosis become manifest at the end of the first decade and may be
rapidly progressive during puberty.

>>subtype A - normal dentition
>>subtype B - dentinogenesis imperfecta

B. Osteogenesis imperfecta type II (aka, Osteogenesis imperfecta congenita, Vrolik Disease).

characteristic features: (usu.) blue sclerae; autosomal recessive/new-mutation
autosomal dominant inheritance pattern; low birth-weight/ short birth-length

*usually lethal in the perinatal period

*prenatal ultrasound (US) examination reveals multiple fractures, and femoral
length >three standard deviations below the mean for gestational age

*innumerable fractures are invariably present at birth, resulting in the shortening
and bowing of the long bones; thin, fragile ribs may fracture with minimal trauma,
and may demonstrate rachitic changes

C. Osteogenesis imperfecta Type III

characteristic features: earlier-occurring (often in utero and more-numerous
fractures than in OI Type I: white sclerae, or bluish sclerae which normalize to
white later in infancy; autosomal recessive/new-mutation autosomal dominant (i.e.,
no family history); occasional hearing impairment

*very early and multiple fractures result in progressive twisting and bowing
deformities of long bones

D. Osteogenesis imperfects Type IV - very rare.

characteristic features: white sclerae, variable degrees of hearing impairment;
autosomal dominant inheritance pattern; variable degrees of osteoporosis and fractures

>>subtype A - normal dentition

>>subtype B - mild dentinogenesis imperfecta

References:
1. "Differential Diagnosis of Skeletal Lesions", in Practical Pediatric Radiology, 2nd ed.,
pages 419-423. S.vW Hilton, MD, and DK Edwards III, MD, eds. WB Saunders, 1994.

2. "Osteogenesis Imperfecta", in Caffey's Pediatric X-ray Diagnosis: An Integrated
Imaging Approach, 9th ed., pages 1676-1680. FN Silverman, MD and JP Kuhn, MD, eds.
Mosby, 1993.

3. Textbook of Disorders of the Musculoskeletal System, 2nd ed., pages 138-139. RB
Salter,M.D. Williams and Wilkins, 1983.

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