Osteomalacia Flashcards
Definition
Osteomalacia is a disorder of mineralisation of bone matrix (osteoid)
It creates softening of the bone and is most commonly caused by severe vitamin D deficiency
o Rickets is a disorder of defective mineralisation of cartilage in the epiphyseal growth plates of children
Risk factors of vitamin D deficiency
o Lack of exposure to sunlight
o Dietary deficiency
o Malabsorption
o Decreased 25-hydroxylation of vitamin D (due to liver disease, anticonvulsants)
o Decrease 1a-hydroxylation of vitamin D (due to chronic kidney disease, hypoparathyroidism)
o Vitamin D resistance
Aetiology
Commonly caused by severe vitamin D deficiency
· Renal Phosphate Wasting
o Fanconi’s syndrome - characterised by:
· Phosphaturia
· Glycosuria
· Amino aciduria
o Renal tubular acidosis (type 2)
o Hereditary hypophosphataemic rickets (X-linked or autosomal dominant)
o Tumour induced osteomalacia
Epidemiology
· COMMON in industrialised countries
· More common in FEMALES
Presenting symptoms (osteomalacia)
o Bone pain (mainly in the axial skeleton)
o Weakness
o Malaise
Presenting symptoms (rickets)
o Hypotonia
o Growth retardation
o Skeletal deformities
Signs on physical examination (osteomalacia)
o Bone tenderness
o Proximal muscle weakness
o Waddling gait
o Signs of hypocalcaemia:
· Trousseau’s sign - inflation of a blood pressure cuff to above the systolic pressure for > 3 mins causes tetanic spasm of the wrist and fingers
· Chvostek’s sign - tapping over the facial nerve causes twitching of the ipsilateral facial muscles
Signs on physical examination (rickets)
o Bossing of frontal and parietal bones
o Swelling of costochondral junctions (rickety rosary)
o Bow legs in early childhood
o ‘Knock knees’ in later childhood
o Short stature
Investigations (bloods)
o Low or normal Ca2+
o Low phosphate
o High ALP
o Low 25-hydroxy vitamin D
o High PTH (secondary hyperparathyroidism)
o Check U&Es
o Check ABGs (for renal tubular acidosis)
o Increased phosphate excreting (in renal phosphate wasting)
Investigations (radiographs)
o May appear normal
o May show osteopaenia
o Looser’s zones = wide, transverse lucencies traversing part way through a bone, usually at right angles to the involved cortex and are associated most frequently with osteomalacia and rickets (AKA pseudofractures)
Investigations (bone biopsy)
· Bone biopsy after double tetracycline labelling
o Tetracycline is deposited at the mineralisation front as a band
o After two course of tetracycline (separated by a few days), the distance between the bands of deposited tetracycline is reduced in osteomalacia
o Not usually necessary for the diagnosis of osteomalacia
Management plan
· Vitamin D and calcium replacement
· Monitor 24 hr urinary calcium
· Also monitor: o Serum calcium o Phosphate o ALP o PTH o Vitamin D
· Treat the underlying CAUSE
Possible complications
· Bone deformities
· Hypocalcaemia can cause epileptic seizures
· Cardiac arrhythmias
· Hypocalcaemic tetany
· Depression
· Hypocalcaemia symptoms = CATs go NUMB o Convulsions o Arrhythmias o Tetany o NUMBness/paraesthesia
Prognosis
· Symptoms and radiological appearances improve with vitamin D treatment
· Bone deformities in children tend to be permanent