Metabolic Bone diseases Asma

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

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

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 t wo hormones control blood calcium levels- parathyroid hormone increases it and calcitonin lowers it.

Vitamin D metabolism

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

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

Calcium Homeostasis

Correction for Hypercalcemia

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

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 d

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..

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

Pseudofractures

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

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 gut,liver,kideny dz

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.

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.

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;

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

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

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.

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

Osteomalacia vs osteoporosis Osteomalacia Osteoporosis Ageing fem, #, decreased bone dens Ill Not ill General ache Asympt till # Weak musclesnormal Loosersnil Alk ph incr normal PO4 decrnormal Ca x PO4 2.4