Rickets Osteomalacia I

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					Rickets Osteomalacia Mankin, Apley, Miller DEF - Deficiency of Ca++ &/or PO4 which results in inadequate osteoid mineralisation - Less mineralised bone / vol of bone - Inc uncalcified osteoid - Rickets = immature skeleton - Osteomalacia = mat skeleton - Bone formation is slowed & unmineralised osteoid accumulates along new bone surfaces - Remember that osteoid is the organic component of woven bone & can be mineralised or unmineralised AETIOL - Vit D Def is classic form - Now less com in developed world - No 1 cause is Hypophosphataemic Rickets (Vit D Resistant) CLASS Mankin 1 Deficiency States - Vit D - Ca++ - PO4 - abn hydroxylation of vit D (rare) - abn receptors (rare) 2 Gastrointestinal - Gastric - Biliary - Enteric 3 Renal Tubular - Vit D Resistant AKA Hypophosphataemic X Linked Rec Fanconi I & II Failure to resorb PO4 - Type I & II Vit D Dependent "Pseudodependent" Rare These pt’s make 1,25D but gut fails to recognise it Type II can respond to oral D3 though - Renal Tubular Acidosis  Fail to retain HCO3 -> lose Na, Cl, K & Ca 4 Renal Osteodystrophy 5 Other - Hypophophatasia - Fibrous Dysplasia / NF - Other Tumours - Anticonvulsants PATHOPHYSIOLOGY 1 Def States Vit D Def - Dec D3 intake / sunlight ç Dec Ca++ absorp GIT » Dec Se Ca++ » 2° HyperPTH » Inc of Se Ca++ Low/N & Dec Se PO4 2° Hyper PTH is the bone problem - Classic form - Us due to: Diet Def Vit D - Elderly, Vegans Min sunlight  Rx Vit D3 & Ca++

Calcium Def - Dec Ca++ intake » As above Dec PO4 via 2° HyperPTH - Seen where dairy products avoided or Ca++ chelates to other substance Chelators v uncommon Bizarre diets Phytate (cereals) Oxalate (spinach) PO4 excess Phosphate Def - Dec PO4 intake » Dec Se PO4 » Inc Renal production 1, 25-D3 » Inc bone resorption - V unusual - 2° precipitation zof insoluble PO4 by: Beryllium (toxin) Al in antacids 2 GI Causes Gastric - Post Gastrectomy - Dec absorp Ca++ 2°: Inc Ph 'Dumping' Biliary (biliary cirrhosis) - Poor D3 absorb ç other fats - Less bile salts - Also Ca++ & FFA = Ca++ soaps Enteric - Dec Ca++ absorp 2° diffuse SI injury IBD Crohn's, coeliac 3 Renal Tubular Causes D3 Resistant - AKA Hypophosphataemic - No1 cause of Ricketts - Genetic / Acquired defect PCT handling of PO4 - No 2° HyperPTH as Se Ca++ not affected Absence 2° hyperPTH - Admin Vit D has little effect - Rx ç Neutral PO4 - Congenital & Acquired forms X Linked Fanconi Syn = AR Acq = ST Tumours X- Linked Hypophosphatemia - AKA Albright's Syn - Most com cong form - X-linked Recessive - Dec PCT PO4 reabsorption - Rx Neutral PO4 Vitamin D Dependent - Rare - Classical features of Vit D def - Really Pseudo-Dependence No response to oral VD - Rx high doses of 1,25-DHCC & Ca++ Type I - Failure of conversion of 25-D to 1, 25-D

- ? abN renal alpha-hydroxylase Type II - End-organ insensitivity to 1, 25-D in Gut -> may respond to exogenous D3 Renal Tubular Acidosis - May be 1° genetic Syn Acquired Syn Part of another disorder - Renal Bicarb wastage Acidotic HypoK+ HypoCa++ Alkaline urine  Release of Ca++ from bone as carbonate used to buffer acidosis Ca++ excreted in urine Bone eroded - Can't Rx ç V3 - Rx ç Na Bicarb to correct Ph Unusual Causes Hypophosphatasia - Rare & inherited - Due to gen dec in tissue non-specific ALP activity - Causes retardation of skel mineralisation - Often severe & fatal Fibrous Dysplasia or NF - Rickets may be rare manifestation - Remember that these 2 share: 1 Café Au Lait Spots ~ Maine 2 Bone Dysplasia 3 Pseudofracture Bone & Soft Tissue Tumours - Us in benign fibrous ST tumours - Due to prod of factors that affect PCT handling PO4 Anticonvulsants - All anti-seizure drugs interfere ç hepatic handling of V3 - V3 converted to inactive metabolites rather than 25-D PATH HISTOL - Cortices thin - Trabeculae thin & irreg - Osteoid seams V wide pathognomonic Trabeculae & cortex Layer of unmineralized bone Surrounds a mineralized bone Physis in Rickets - Reserve & proliferative zones are essentially N - Hypertrophic zone disordered - Greatly widened & inc in ht - Orderly columnization lost - Tongues of hypertrophic cells extend down into metaphysis  Ht inc as cells don't release Ca ++ & remain alive - Metaphysis abN Matrix not calcified Few spicules of bone that do form are poorly mineralized Wide osteoid seams present CLIN Rickets Growth

- Short - Wt unaffected - Rachitic pot-belly - "Buddha like" Activity - Apathetic - Prefer to sit - Irritable - Weak - If sev » Unable to walk Skull - Soft - Craniotabes - Prominent sutures - Hot-Cross skull - Frontal bossing Teeth - Enamel defects - Extensive caries Thorax - Prominent costochondral j'ns - Rachitic Rosary - Pectus Carinatum - Harrison's Groove - Rib sulcus at diaphragm insertion Spine - T Kyphosis - Rachitic cat-back Extremities - Enlargement of wrists, elbows, ankles & knees - Bowing deformity of long bones - esp. Legs » Bowed / Knock knees - Path # - SUFE Osteomalacia - Min findings - Malaise & easy fatiguability - Bone pain & tenderness - May present ç back pain - Prox muscle weakness - Trendelenburg gait Ix Biochemical - Low or low-N Ca++ - Low PO4- Ca++ /PO4 index low Ca++ x PO4 < 2.4 (N > 3) --> diagnostic - High ALP - PTH N or high - Low Se 25-D3 - In osteoporosis all this should be N - Definitive Dx = Tetracycline labelled Bone Bx Plain XR General Rickets - 1° affects physis - But bones may show changes of 2° hyperPTH Osteomalacia - Affects only bones - Changes less evident Bones less active - May also see changes of 2° hyperPTH - Osseous changes ç indistinct fuzzy trabeculae ç ground-glass appearance & thin cortices - May be: Bowing Pathol # Rickets - Growth plate changes characteristic Physis - Enormous inc in ht of physis

- Irregular cupping & flaring of metaphysis - Failure of mineralisation of metaphysis

2ndry HyperPTH - Subperiosteal erosions in areas of max remodelling - Med borders of: Proximal humerus Femoral neck Distal femur Proximal tibia - Lat borders of: Distal radius Distal ulna - Adults tend to resorb bone at rad border P2 middle finger & Brown tumours Osteomalacia - Three characteristic features 1 Looser's Lines Syn. Milkman's pseudo# - "The stamp of Osteomalaciae" - Ribbon-like linear radiolucent lines - Transverse to long axis - Often don't extend completely across bone - Are insufficiency # that have healed ç unmineralised callus # Concave side of long bones (opposite side to stress fractures) Medial femoral neck Ischial and pubic rami Ribs, clavicles Axillary border of scapulae - May propagate 2 Codfish Vertebrae - May be multiple vertebral compression # from disc pressure - Result is biconcave vert 3 Trefoil Pelvis - AKA Arthrokatadysis / protrusio - Bi -lateral indentation of acetabulum - Gives appearance of champagne glass or trefoil Bone Scan - Patchy areas of inc uptake - Looser's zones are active

REGULATION OF CALCIUM AND PHOSPHATE METABOLISM

Origin

Factor s   2+ [Ca ]

Factors   [Ca ]  1,25...
2+

PTH peptide

chief cells parathyroid gland

1,25(OH)2D steroid

prox tubule of kidney

Calcitonin

para follic. cells of thyroid

[ 2+ ca ] [phos]  PTH 2+  [ca ]

 [Ca ]  [phos]  PTH
2+

Effects on intestine No direct affect,  absorptio n of Ca indirectly via  1,25 D3 abs of Ca  abs of phos

Effects on kidney  D3 reabsorption of calcium,  excretion of phosphate

Effects on bone

Effects on [ca] 

Stimulates osteoclasts to absorb bone, stimulates recruitment of preosteoclasts

Effects on [pho] 

stimulates reabsorption of bone (osteoclastic) inhibits osteoclaststic reabsorption of bone





 [ca ]
2+

transie nt 


				
Lingjuan Ma Lingjuan Ma
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