Osteomalacia and rickets

OSTEOMALACIA & RICKETS

Abdullah

Taskeen

DIFINATION :

Rickets :

osteopenia with disordered calcification leading to higher proportion of osteoid (unmineralized) tissue prior to epiphyseal closure (in childhood)

osteomalacia :

osteopenia with disordered calcification leading to higher proportion of osteoid (unmineralized) tissue after epiphyseal closure (in adulthood)

BASIC:

Bone consists of :

A- a hard outer shell (cortex) made up of minerals, mainly calcium and phosphorus,

B- a softer inner mesh (matrix) made up of collagen fibres.

WHEN NORMAL BONE IS FORMED :

A - these fibres are coated by mineral (this process is called mineralisation).

B - The strength of the new bone depends on enough mineral covering the collagen matrix.

The more mineral laid down, the stronger the bone.

OSTEOMALACIA HAPPENS : A. if mineralisation doesn’t take place properly.

B. bone is made up of collagen matrix without a mineral covering,

C. so the bones become soft.

D. These softened bones may bend and crack, and this can be very painful.

AGAIN !! DIFINATION :

Rickets :

osteopenia with disordered calcification leading to higher proportion of osteoid (unmineralized) tissue prior to epiphyseal closure (in childhood)

osteomalacia :

osteopenia with disordered calcification leading to higher proportion of osteoid (unmineralized) tissue after epiphyseal closure (in adulthood)

ETIOLOGY AND PATHOPHYSIOLOGY

A. Vitamin D Deficiency

B. Mineralization Defect

C. Phosphate Deficiency

CLINICAL PRESENTATION :

INVESTIGATION :

OTHERS :

Serum 25OHD = low ( exept in V. D resistance rickets )

Serum fibroblast FGF-23 = elevated in tumor associated osteomalcia

RADIOLOGIC FINDINGS - pseudofractures,

‘Looser’s zones’

- Linear areas of low density surrounded by sclerotic

borders.

- loss of radiologic distinctness of vertebral bod trabecula,

- concavity of the vertebral bodies

- narrow radiolucent lines (healed stress fractures )

Looser Zones

Looser Zones

diffuse osteopenia and several insufficiency stress fractures of the bilateral ribs (arrows) and scapulae

Stress fracture

several insufficiency stress fractures in the right femoral lesser trochanter, both femoral necks (arrows), acetabula (arrowhead), and pubic rami (white arrow).

Stress fracture

GOLD STANDARD Bone biopsy :

A. Increased osteoid width (> 15 μm),

B. increased mineralization lag time, and

C. lack of Uptake of double tetracycline labelling in osteoid seams.

ostoid ( pink ) > 80 % Ostoid thickness > 12 um

Mineralization lag time > 100 days

RX: - depends on the underlying cause

• vitamin D supplementation • PO4 supplements if low serum PO4 is present

• Ca supplements for isolated calcium deficiency

• bicarbonate if chronic acidosis

RX :

calcitriol or alfacalcidol

there is defective 1α-hydroxylation,

e.g. chronic kidney disease, vitamin D dependency and hypophosphataemic rickets with osteomalacia.

REFERENCES :

Kummar & clarck 7th edition

MD- consult

Good bye !!