RICKETS/OSTEOMALACIA

•7 month old female Pomeranian• Hx: Hypocalcemia, hyperphosphatemia•Accession 86423•MRN 136554

Flared metaphyses Widened, lucent physes “Cupping” of physes

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.

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

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

Hyperadrenocorticism Osteogenesis imperfecta Other causes of decreased collagen or

matrix production

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)

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

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

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

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

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

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

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

•Dietary•Renal failure•Liver disease•Pancreas/small intestinal dz•Hypoparathyroidism