with decreased rates of mineral apposition on tetracycline labeling.
– vitamin D resistant rickets is also known as familial hypophosphatemic rickets and is inherited as a sex-linked dominant trait; it is caused by a renal inability to handle phosphate (there are a number of types of vitamin D resistant rickets, of which this is type I.
– secondary gout is associated with myeloproliferative and lymphoproliferative disorders such as multiple myeloma, leukemia, erythrocytosis, and hemolytic diseases such as sickle cell
– for newly diagnosed CPPD, you should get the following bloodwork: calcium, magnesium, phosphorus, glucose, alk phos, ferritin, iron and iron binding capacity, TSH, and uric acid. Patients with hemochromatosis often get a CPPD picture, and you should rule this out. Ochronosis is also associated with CPPD.
Ochronisis (Alkaptonuria) – rare, inherited deficiency of homogentisic acid oxidase; homogentisic acid is retained in the body and deposited as a pigmented polymer in the cartilage, skin, and sclerae (the darkening of these tissues is called ochronosis). Because the pigment is preferentially deposited in cartilage, a degenerative arthropathy is inevitable, beginning in the 4th decade. It begins in the spine with multiple vacuum discs, then the entire spine showing ossification of discs and or narrowing and collapse. Look for chondrocalcinosis in multiple joints. Look for a history of passing dark urine, or fresh urine turning black on standing.
Hemochromatosis – autosomal recessive disorder causing excessive body iron stores and deposition of hemosiderin causing tissue damage and organ dysfunction. Markedly elevated ferritin; increased serum iron concentration with at least 60% saturation of serum iron-binding transferrin. Diagnosis is confirmed by liver biopsy (the liver is radiodense too) showing hemosiderin in parenchymal cells; also may show fibrosis, cirrhosis, or even hepatoma. Chondrocalcinosis is characteristic of the arthropathy and a radiographic feature at some time in 50% of patients. The finding of chondrocalcinosis should always suggest the possibility of hemochromatosis. The arthropathy usually is of the hands, especially MCP (2 and 3) and PIP joints. May also get shoulders, knees, hips.
– the large, radiodense liver is the MCQ tip-off to think of hemochromatosis!
– PTH influences calcium hemostasis by influencing vitamin D production (amongst other things). Also gets osteoclasts working, and increases renal excretion of phosphate. Via vitamin D, it increases calcium absorption in the gut, increases calcium reabsorption in the kidney, and increases calcium breakdown from bone.
– vitamin D (1,25 (OH)2 Vit D) is the most important for gut absorption of calcium
– PTH does not work on the hydroxylation of vitamin D in the liver; it works at the kidney!
– osteocytes are directly stimulated by calcitonin and inhibited by PTH; ? decrease serum calcium with calcitonin is due to osteocytes working to lay down bone?
– carpo-pedal spasm is caused by hypocalcemia
– remember Mankin’s rules: nerve, brain, skeletal muscle – irritability is inversely proportional to calcium; while cardiac muscle irritability is directly proportional to calcium.
– hypercalcemia – polyuria (phosphate diuresis), poydipsia, constipation, lethargy, disorientation, hyporeflexia,
– renal osteodystrophy patients may have leg pain from extraskeletal calcification, fractures through Looser’s lines, periostitis, and osteitis fibrosa (subperiosteal erosions)
– steroids produce bone loss primarily by suppressing osteoblasts. It inhibits intestinal calcium absorption, leading to mild secondary hyperPTH and osteoclastic absorption. It also stimulates renal calcium excretion.
– myositis ossificans progressiva – has increased alk phos
– The x-ray findings of patients with rickets: widened physis. The epiphyseal line is irregular, cupped, or widened. The zone of provisional calcification, which is ordinarily a thin dense white line on x-rays, appears
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