osteogenesis imperfecta

also known as

brittle bone disease

disorder of collagen synthesis leads to recurrent fractures and deformation

incidence

type I most common

equal among males and females and racial groups

etiology

most inherit from parent (autosomal dominant)

25% of cases, genetic mutation occurs

pathophys

defect in collagen synthesis

more than 150 mutations

type 1 collagen (major structural component in ECM of bone, skin, tendons)

mutated gene instructs body to make either too little type 1 collagen or abnormal polypeptide chains that cannot form the triple helix of type 1 collagen

type 1 is least severe (collagen production reduced by 50%

type 2 is severe ( collagen production reduced by 80%)

diagnostic tools

DNA testing

prenatal ultrasound (identify fractures after 15 weeks)

fetal 3D CT scan

human chorionic villus biopsy (piece of placenta at 14-20 weeks)

DEXA (low bone mineral density)

x-ray films (multiple old fractures, skeletal deformities, long bone with thin radiolucent appearance, malformed ribs)

type 1

most common

mildest

2 types: A-teeth are normal, B- dentinogensis imperfecta (abnormal tooth development)

grayish-blue sclerae at birth

mild to mod bone fragility

osteopenia

mild femoral bowing at birth

generalized ligamentous laxity with joint hypermobility

50% develop hearing loss by teens

type 2

most severe form

lethal: mainly due to pulmonary complications from rib and vertebral fractures

severe bone fragility

at birth, short limbs, small chests, and soft skulls

sclerae dark blue or gray

intrauterine fractures common

respiratory and swallowing problems

type 3

severe

usually result of new mutations

fractures and deformities from utero

large skull-upper protion-triangular face

dentinogenesis imperfecta

blue to pale blue sclerae

healing is impaired

severe osteopenia

severe disorganized growth plate structure

progressive kyphoscoliosis

early onset hearing loss

very short stature

lifespan may be shortened due to respiratory conditions

type 4

moderate form

dx can be made at birth but often occurs later

normal birth weight and length

2 subsets: A-normal dentition, B-dentinogenesis imperfecta (majority)

slightly gray sclerae

moderate bone fragility

mild femoral bowing at birth

osteopenia occurs with aging

scoliosis

mild bone angulation

child might not fracture until walking

prognosis

types 1 and 4 milder course, normal lifespan

type 2 most severe, 90% die in first few weeks

type 3 mortality related to cardiorespiratory failure stemming from kyphoscoliotic deformity (significant risk also exists of basilar invagination of skull and intracranial bleeding

clinical features

brittle bones

joint hypermobility

thin skin

weak muscles

diffuse osteoporosis

shortened stature

multiple recurrent ffractures

blue sclerae

deformed teeth

deafness

hernias

easy bruising

excessive sweating

scoliosis

pectus deformity

metabolic defects

cardiovascular complications

triangular face with types 3 and 4

developmental motor skills often delayed

medical management

no cure

manage fractures

promote function and independence

fractures

most heal well

short-term immobilization

prevention important

treatment options: surgery, medications, healthy lifestyle, PT

surgery

rodding: metal rods inserted into long bones to control fractures and improve deformities associated with decreased function

progressive scoliosis: bracing not usually recommended (force from brace can deform ribs rather than straighten spine), spinal rodding may be indicated in severe cases

medications

biphosphonate drugs (slows loss of bone but doesn’t build new, reduces long bone fractures/vertebral compression)

others being researched: GH, stem cell therapies, anti-sclerostin antibody, current antibody studies

healthy lifestyle

adequate intake of calcium (maintain bone density), vitamin C (promote healing)

avoid smoking, alcohol, caffeine, steroid medications

genetic counseling

role of PT

protective handling and positioning

strengthening

adaptive equipment

ambulation

post-surgery

aquatics

education/pervention

ambulation

type 1: majority of children ambulate wither as functional or household ambulators, 50% can walk independently in community

type 3: about half are dependent on pwer mobility, only 27% household ambulators

type 4: 26% community ambulators, 57% household ambulators

best predictor of ambulatory status are disease type and ability to sit by 9 or 10 months

role of PT precautions

always be aware of infants limbs

severe: use pillow for transporting baby

allow infant to explore independent movement

support in many positions (allows muscles to develop to aide in sitting and standing)

DO: lift infant by placing hand under butt and legs and other under shoulders, neck, and head

DO NOT: push or pull a limb, lift and infant from under armpits, lift by ankles, perform activities that will jar or twist spine

role of PT education

teach family how to care and handle baby

promote independent function: teach family and patient how to modify home and school environment to accommodate their short stature and low strength

local support group