Osteomalacia (& vitamin D deficiency) Flashcards
Define osteomalacia
Disorder of disorganised bone matrix (osteoid)
Define rickets
disorder of defective mineralisation of cartilage in epiphyseal growth plates of children
Risk factors for osteomalacia
2 groups
Vitamin D deficiency
Renal phosphate wasting
Risk factors for osteomalacia - vitamin D deficiency
6
Lack of exposure to sunlight
Dietary deficiency
Malabsorption
Decreased 25-hydroxylation of vitamin D (due to liver disease, anticonvulsants)
Decreased 1α-hydroxylation of vitamin D (due to chronic kidney disease, hypoparathyroidism)
Vitamin D resistance
Risk factors for osteomalacia - renal phosphate wasting
4
Fanconi’s syndrome
characterised by: phosphaturia, glycosuria, amino aciduria
Renal tubular acidosis (type 2)
Hereditary hypophosphataemic rickets (X-linked or autosomal dominant)
Tumour induced osteomalacia
Epidemiology of osteomalacia
prevalence, gender
COMMON in industrialised countries
More common in FEMALES
Presenting symptoms of osteomalacia
3
Bone pain (mainly in axial skeleton)
Weakness
Malaise
Presenting symptoms of rickets
3
Hypotonia
Growth retardation
Skeletal deformities
Signs of osteomalacia on physical examination
5
Bone tenderness
Proximal muscle weakness
Waddling gait
Signs of hypocalcaemia:
Trousseau’s sign: inflation of BP cuff to above systolic pressure for >3mins causes titanic spasm of wrist & fingers
Chvostek’s sign: tapping over facial nerve cause twitching of ipsilateral facial muscles
Signs of rickets on physical examination
5
Bossing of frontal & parietal bones Swelling of costochondral junctions (rickety rosary) Bow legs in early childhood “Knock knees” in later childhood Short stature
Investigations for osteomalacia
3 groups
Bloods
Radiographs
Bone biopsy after double tetracycline labelling
Investigations for osteomalacia - bloods
8
Low or normal Ca2+ Low phosphate High ALP Low 25-hydroxy vitamin D High PTH (secondary hyperparathyroidism) U&Es ABGs (for renal tubular acidosis) Increased phosphate excreting (in renal phosphate wasting)
Investigations for osteomalacia - radiographs
3
May appear normal
May show osteopenia
Looser’s zones
Investigations for osteomalacia - bone biopsy after double tetracycline labelling
(3)
Tetracycline is deposited at mineralisation front as a band
After 2 courses of tetracycline (separated by a few days) the distance between the bands of deposited tetracycline is reduced in osteomalacia
Not usually necessary for diagnosis
Define Looser’s zones
wide transverse lucencies transversing part way through a bone, usually at right angles to the involved cortex & associated most frequently w/ osteomalacia & rickets (AKA pseudofractures)
