dysplasias affecting bone density

Osteopetrosis

definition

·      syn. marble bone disease

·      abnormally dense bones from disorder of osteoclasis

epidemiology

·      two forms

Tarda

·      adult form

·      relatively benign

·      autosomal dominant

Congenita

·      infantile form

·      more severe

·      autosomal recessive

pathology

·      diminished bone resorption due to osteoclast defect

·      may be due to immune thymic defect

·      bones exceedingly dense

·      marrow spaces and foraminae encroached upon by bone

·      bone fragile

·      tongues of cartilage persist at sites of enchondral bone formation

·      may project into metaphysis

·      are calcified (cf. rickets)

clinical features
Tarda

·      may be unaffected

·      often chance diagnosis

·      may see

·      mild anaemia

·      facial palsy

·      deafness

·      fractures

·      prone to osteomyelitis after tooth extraction

Congenita

·      presents in infancy

·      failure to thrive

·      marrow failure

·      easy bruising and bleeding

·      pancytopaenia

·      hepatosplenomegaly

·      multiple fractures

·      cranial nerve palsies

·      esp. optic, facial

·      death from repeated haemorrhage or overwhelming infection

radiology

·      increased density of all bones

·      widened cortices and narrow medullary cavity

·      bone within bone appearance

·      flask-shaped metaphyses

·      sclerotic vertebral endplates

·      produce striped appearance (rugger-jersey)

·      skull thickened and sclerotic

Pyknodysostosis

·      Henri Toulouse-Lautrec was sufferer

·      characterised by

·      shortness of stature

·      frontal bossing

·      underdevelopment of mandible

·      x-rays show increased bone density

·      may be confused with OI because of

·      blue sclerae

·      pathological fracture

Abnormal bones

candle bones

·      melorheostosis

·      pain and stiffness in one limb

·      x-rays show irregular patches of sclerosis

·      in linear fashion through limb

·      looks like wax on side of candle

spotted bones

·      osteopoikilosis

·      numerous white spots on x-rays of many bones

·      may be whitish spots in skin

striped bones

·      osteopathia striata

·      x-rays show lines of increased density parallel to shafts of long bones