Osteogenesis imperfecta
Introduction
Brittle bone disease with varying degrees of severity.
Etiology
- deficiency in the synthesis of type 1 collagen which is found in bone, skin, dentin, ligaments and tendons
- decreased synthesis of normal collagen in mild forms, synthesis of abnormal collagen chains in severe and lethal types
- inherited both in autosomal dominant and autosomal recessive trait
Clinical signs
- skeletal fragility, multiple fractures
- dentinogenesis imperfecta
- hearing loss
- laxity of the joints
- excessive sweating
- fragile skin
- certain types present with blue sclerae which may later become white
Broad range of phenotypes.
Classification according to Silence in 4 major subtypes:
Type II. is uniformly lethal, type I., III. and IV. compatible
with survival.
Type II. is the most common type seen by the
pathologist. Prenatal diagnosis and termination of pregnancy
is possible in severe types of OI.
Clinical signs
- Type II.
- the most severe form
- extreme skeletal fragility
- multiple fractures occur form movement in utero
- skeletal deformity — limb shortening, bowing of
long bones
- small bell shaped thorax
- the head is speherical and soft (poor osification)
- death occurs in utero or within days after birth due to
intracranial hemorrhage or respiratory insuficiency
(lung hypoplasia).
- the majority of cases are new dominant mutations
- Type III.
- progressive deformity of long bones and spine
- compatible with survival
- multiple fractures (dozens), some may be found even at birth
- short and bowed long bones
- progressive kyphoscoliosis
- short stature
- wheel-chair dependence
- life span is shortened
- Type I.
- mild fragility
- postnatal fractures
- blue sclerae
- Type IV.
- moderate fragility
- postnatal fractures
- white sclerae
- prognosis is much better than in type III.
Pictures
Osteogenesis imperfecta:
Osteogenesis imperfecta, Macro, autopsy (73692)
Osteogenesis imperfecta type II., macro and US video:
Osteogenesis imperfecta, Macro, autopsy (73693)
Osteogenesis imperfecta, Macro, autopsy (73694)
Osteogenesis imperfecta, Macro, autopsy (73695)
Osteogenesis imperfecta, type II., Ultrasound, video (74027)
Histology
- osteopenia — thin, delicate cortical and trabecular bone
- fractures with callus formation
- cartilage growth plate is normal
