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RICKETS/OSTEOMALACIA

RICKETS/OSTEOMALACIA. The case of Sunset Sky. Sunset Sky Davis. 7 month old female Pomeranian Hx: Hypocalcemia, hyperphosphatemia Accession 86423 MRN 136554. Radiographic signs. Flared metaphyses Widened, lucent physes “Cupping” of physes. Diagnostic Testing.

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RICKETS/OSTEOMALACIA

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  1. RICKETS/OSTEOMALACIA The case of Sunset Sky

  2. Sunset Sky Davis 7 month old female Pomeranian Hx: Hypocalcemia, hyperphosphatemia Accession 86423 MRN 136554

  3. Radiographic signs • Flared metaphyses • Widened, lucent physes • “Cupping” of physes

  4. Diagnostic Testing • 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.

  5. Metabolic Bone Disease Osteolysis (i.e.—hyperparathyroid states) Defective Bone Formation • Nutritional sec. • Renal sec. • Primary Defective osteoid production (aka Osteoporosis) Inadequate mineralization of osteoid (RICKETS) • HAC • Osteogenesis imperfecta • Renal sec. • Decr. Ca or P • VITAMIN D DEF. • Hepatic • anticonvulsant

  6. Osteolysis • Nutritional—too much P or too little Ca causes PTH secretionbone resorption • Renal secondary—inadequate P excretionhypocalcemiaPTH secretionbone resorption • Hypercalcemia of malignancy (PTHrp) • Primary hyperPTH

  7. Causes of Osteoporosis (decreased osteoid production) • Hyperadrenocorticism • Osteogenesis imperfecta • Other causes of decreased collagen or matrix production

  8. Causes of Inadequate Min. • 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)

  9. Dietary-Related Skeletal Changes in a Shetland Sheepdog Puppy • 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

  10. Bottom line: Nutritional Rickets • 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

  11. Interesting points • 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

  12. Vitamin D-Dependent Rickets Type II in a Cat • 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) Journalof Small Animal Practice (2005); 46:440-444

  13. Unable to utilize vitamin D appropriately • 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

  14. How to test vit D receptors?? • 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

  15. 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

  16. Over 30 diseases can decrease vitamin D absorption, metabolism, or actions! Dietary Renal failure Liver disease Pancreas/small intestinal dz Hypoparathyroidism

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