This document discusses metabolic bone diseases including osteomalacia and rickets. It provides details on bone histology, calcium homeostasis, vitamin D metabolism, and the roles of parathyroid hormone and calcitonin in regulating calcium levels. It describes the causes, clinical features, investigations and treatments of osteomalacia and rickets. Osteomalacia is characterized by softening of bones from defective mineralization in adults, while rickets causes softening of bones and growth plate abnormalities in children, often due to vitamin D or calcium deficiencies.

1. Metabolic Bone
diseases
Asma

2. Bone Histology
• Recall that bone is a connective tissue that
consists of a matrix, cells, and fibers
• Bone matrix
– Resembles reinforced concrete. Rebar is collagen
fibers, cement is hydroxyapetite
– Organic components (35%)
• Composed of cells, fibers and organic substances
(osteoid)
• Collagen is most abundant organic substance
– Inorganic mineral salts (65%):
• Primarily calcium phosphate (hydroxyapatites)
• Gives bone its hardness; resists compression

3. Bone Matrix
• If mineral removed, bone is too bendable
• If collagen removed, bone is too brittle

4. Calcium Homeostasis
• Bone is major storage site for calcium
• The level of calcium in the blood
depends upon movement of calcium
into or out of bone.
• Calcium metabolism is regulated by:
Vitamin D, and two hormones control
blood calcium levels- parathyroid hormone
increases it and calcitonin lowers it.

5. Vitamin D metabolism

6. Vitamin D: The Sunshine Vitamin
• Not always
essential
– Body can make it if
exposed to enough
sunlight
– Made from
cholesterol in the
skin

7. Parathormone
– Parathyroid hormone
• Primary regulator of calcium
homeostasis
• Stimulates bone resorption
• Increases renal reabsorption of
calcium from urine
• Stimulates vitamin D activation
• Increase Calcium absorption from
gut

8. Calcium Homeostasis

9. Correction for Hypercalcemia

12. Osteomalacia
Osteomalacia is the general term for the
softening of the bones due to defective bone
mineralization.
Osteomalacia in children is known as rickets,
A common cause of the disease is a deficiency in
vitamin D, which is normally obtained from the
diet and/or sunlight exposure

13. Causes
• Insufficient sunlight exposure,
especially in dark-skinned subjects
• Insufficient nutritional quantities or
faulty metabolism of vitamin D or
phosphorus
• Renal tubular acidosis
• Malnutrition during pregnancy
• Malabsorption syndrome
• Chronic renal failure
• Summery it occure duto defect in
anywhere of metabolic pathway of vit

14. Clinical features
Sympotom usually appear insidiously
Bone pain
Bachach
Muscle weakness
This may be present for years before diagnosis is made
Ofetn the condtion suspected only when the patient admited
to hospital with vertebtal comparsson fractue or insuffcinsy
fracture of femer and tibia.
• Pathologic fractures due to weight bearing may develop. .

15. X - rays
Osteomalacia
• Osteopenia
• Looser zone ,
• biconcave vertebra ,
• Spontaneous fractures

17. Pseudofractures

18. Investigations
• Calcium
• Phosphorus
• Alkaline phosphatase
• Investgation for malabsorbation
syndrom liver disorder and renel
dieases

19. Treatement
• Vit. D + Ca supplyment eldery pt
may need very larg dose up
to2000 iu per day
• fracture management
• correct deformity if needed
• Treatment underlying disorder as

20. Rickets
• Rickets is a softening of the bone due to
deficient mineralization at the growth plate.
• It is common in children and is potentially
leading to fractures and deformity.
• Rickets is among the most frequent childhood
diseases in many developing countries. The
predominant cause is a vitamin D deficiency,
but lack of adequate calcium in the diet may
also lead to rickets.

21. Etiology
• Deficient Intake: Ca, Ph, Vit D.
• Poor absorption: vit D ↓, pseudo vit D↓, vit D
resistance, high phytin content( soy formula),
antacids, anticonvulsants, renal insufficiency, Fanconi
syndrome, hepatic insufficiency, fat malabsorption
(cystic fibrosis).
• Increased excretion: furosemide, renal tubular
dysfunction( phosphaturia, RTA with hypercalciuria),
renal tubular damage e.g. cystinosis, tyrosinosis,
galactosemia, fructose intolerance, wilson disease.

22. Clinical features of Rickets
• GENERAL
– Failure to thrive; Listlessness;
– Protuding abdomen;
– Muscle weakness (especially proximal);
• HEAD
– Craniotabes;
– Frontal bossing;
– Delayed fontanelle closure;
– Delayed dentition; caries;

23. c/f
• CHEST
– Rachitic rosary;
– Harrison groove;
– Respiratory infections and
– atelectasis
• BACK Scoliosis ,Kyphosis ,Lordosis

24. c/f
• EXTREMITIES
– Enlargement of wrists and ankles;
– Valgus or varus deformities
– Bowing of the tibia and femur;
– Coxa vara;
– Leg pain.
• HYPOCALCEMIC SYMPTOMS
– Tetany ; Seizures; Stridor due to laryngeal spasm

28. Biochemical findings in rickets
• Alkaline phosphatase usually is ↑in all forms
of rickets.
• Serum phosphorus concentrations usually
are↓.
• Serum Ca is ↓only in hypocalcemic rickets.
• Serum parathyroid hormone typically is ↑in
hypocalcemic rickets, in contrast it is N in
hypophosphatemic rickets.

29. Treatment of Rickets
• Vitamin D.
• Adequate dietary Calcium & phosphorus provided by milk, formula &
other dairy products. Or added to vitamin D prescriptions
• Symptomatic hypocalcaemia need IV CaCl as 20mg/kg or Ca
gluconate as 100mg/kg as a bolus, followed by oral calcium tapered
over 2-6 weeks.
• Health education
• Treatement of the cause if possible

31. Osteomalacia vs osteoporosis
Osteomalacia Osteoporosis
Ageing fem, #, decreased bone dens
Ill Not ill
General ache Asympt till #
Weak muscles normal
Loosers nil
Alk ph incr normal
PO4 decr normal
Ca x PO4 <2.4 Ca x PO4 >2.4