RICKETS/OSTEOMALACIA
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Transcript of RICKETS/OSTEOMALACIA
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•7 month old female Pomeranian• Hx: Hypocalcemia, hyperphosphatemia•Accession 86423•MRN 136554
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Flared metaphyses Widened, lucent physes “Cupping” of physes
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Increased PTH 90.7 (3-17) Low ionized Calcium 0.94 (1.25-1.45) Low vitamin D 43 (60-215)
These findings are consistent with nutritional sec. hyperPTH with decreased vitamin D intake/GI absorption. Strange, since other pups in household are unaffected.
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Metabolic Bone Disease
Osteolysis(i.e.—hyperparathyroid states)
Defective Bone Formation
Inadequate mineralization of osteoid (RICKETS)
Defective osteoid production (aka Osteoporosis)
•Nutritional sec.•Renal sec.•Primary
•HAC•Osteogenesis imperfecta
•Renal sec.•Decr. Ca or P•VITAMIN D DEF.•Hepatic•anticonvulsant
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Nutritional—too much P or too little Ca causes PTH secretionbone resorption
Renal secondary—inadequate P excretionhypocalcemiaPTH secretionbone resorption
Hypercalcemia of malignancy (PTHrp) Primary hyperPTH
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Hyperadrenocorticism Osteogenesis imperfecta Other causes of decreased collagen or
matrix production
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USUALLY HYPOVITAMINOSIS D --inadequate intake --disorders of vitamin D metabolism --renal failure (decreased synth. Of 1, 25-(OH)2-vitD—the most active) Decreased Calcium or phosphorus intake
(e.g.—inappropriate feeding of renal diets)
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10 wk old Sheltie Suspected renal failure (azotemia, isosthenuria) Placed on a commercial renal failure diet (low
phosphorus/low protein/adequate vit D)
Presented with carpal varus and failure to grow Radiographs—consistent with rickets
J Am Anim Hosp Assoc 2006; 42:57-64
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Note: serum PTH was LOW due to low phosphorus intake (in nutritional sec. hyperPTH, the PTH goes UP in response to decreased Ca)
Hypophosphatemia/Normocalcemia Treatment: commercial puppy food
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In this case, PTH was low because of decreased P, rather than decreased Ca.
Both nutritional sec. hyperPTH and vitamin D deficient rickets can present with HIGH PTH levels.
So, diagnosis can be complex—must carefully analyze diet
Ca:P is ideally 1:1, no higher than 1:2
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4 month old male DSH Presented for inappetence and decreased
mobility
Radiographic signs of rickets Fed adult food/chicken/white fish
Changed to a commercial kitten food Signs continued to progress (devel. rachitic
rosary)
Journal of Small Animal Practice (2005); 46:440-444
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PTH concentrations were HIGH Calcium levels were slightly LOW Phosphorus levels were normal
At 20 mos, plasma 1,25-(OH)2-vitD concentrations were VERY HIGH
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Skin biopsy Obtain fibroblast cultures Test for ability of radiolabelled 1,25-
(OH)2-vit D to bind to nuclear extracts
This cat showed complete lack of binding
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Dietary Vitamin D Intake
Liver converts to 25-OH-vit D
Kidney—proximal tubules convert to 1,25-(OH)2-vit D, the most active form
1, 25-(OH)2-vit D tells GI to absorb more Calcium
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•Dietary•Renal failure•Liver disease•Pancreas/small intestinal dz•Hypoparathyroidism