Biochemical Disorders of Bone Flashcards
What is osteoporosis?
Reduced bone mineral density, increased porosity
quantitative defect - bone of normal quality, just not enough of it
What is the definition of osteopenia?
1 - 2.5 SD below mean peak bone mass
What is the definition of osteoporosis?
> 2.5 SD below mean peak bone mass
How is osteoporosis diagnosed?
DEXA scan –> bone mineral density
What would calcium and phosphate values be in osteoporosis?
Normal
What are some risk factors for primary osteoporosis?
Early menopause Smoking Alcohol Lack of exercise Poor diet Reduced vitamin D exposure
What are some causes of secondary osteoporosis?
Corticosteroids Alcohol abuse Malnutrition CKD Malignancy RA Cushing's Hyperthyroidism Hyperparathyroidism
What is the aim of management in osteoporosis?
Cannot reverse damage
Aim is to slow progression and decrease risk of fracture
What is the treatment for osteoporosis?
Calcium + vitamin D supplements if low intake
Bisphosphonates e.g. alendronate
Others: desunomab, strontium
HRT not considered first line but can be used if SEs to other drugs occur
What is osteomalacia?
Qualitative defect - abnormal softening of bone due to inadequate calcium + phosphorus
What is Rickets?
Osteomalacia in children –> effects growing skeleton
What are some of the causes of osteomalacia/rickets?
Malnutrition/malabsorption
Lack of sunlight (vitamin D stimulates calcium absorption)
Low phosphate: re-feeding, alcohol abuse, malabsorption, renal tubular acidosis
Long term anticonvulsant
CKD
What are the clinical features in osteomalacia/rickets?
Bone pain
Deformities due to soft bones (rickets)
Symptoms of hypocalcaemia
Pseudofractures on xray
What are the symptoms that may be seen with hypocalcaemia?
Paraesthesia Muscle cramps Irritability Fatigue Seizures Brittle nails
Give some examples of deformities seen in Rickets
Bowed legs
Square head
Pigeon chest
Rickety rosary - nodules at costochondral junctions
Describe the biochemical markers in osteomalacia
Low calcium + phosphate
High ALP
What is the management for osteomalacia/rickets?
Vitamin D therapy +
calcium + phosphate replacement
What effect does hyperparathyroidism have off bones?
Hypercalcaemia
Osteoporosis, Brown tumours + osteitis fibroma cystica
What are brown tumours + osteitis fibroma cystica?
Lytic bone lesions - mass of reactive tissue
Can become cystic –> osteitis fibroma cystica (rare late stage)
What are the biochemical features of hyperparathyroidism bone disease?
High PTH
High calcium
Low/normal phosphate
What is Paget’s disease?
Abnormality of bone turnover –> thickened, brittle, mis-shaped bones
What are the clinical features of Paget’s disease?
Arthritis
Deformity
Pathological fractures
Bone pain
Conductive deafness due to involvement of ear ossicles
Increased blood flow through bone –> high output cardiac failure
What would biochemical markers show in Paget’s disease?
High ALP
Normal calcium + phosphate
What would be seen on xray in Paget’s disease?
Enlarged bones
Thickened cortices
Course thickened trabeculae
Mixed areas of lysis and sclerosis
What is the treatment for Paget’s disease?
Bisphosphonates
Calcitonin if extensive lytic disease
What is renal osteodystrophy?
Bone changes due to CKD:
- osteomalacia, sclerosis of bone + calcification of soft tissue
What are the side effects of bisphosphonates?
Oesophagitis
Gastritis
Osteonecrosis of jaw
Fever, myalgia + arthralgia
