Complications
On x-ray, pseudofractures, also known as Looser's zones or Milkman's fractures, represent radiolucent bands perpendicular to the surface of the bones. Analgesia for bone pain and treatment of the underlying cause of osteomalacia are sufficient.
Long-term administration of phosphate supplements can stimulate parathyroid activity, which can lead to a further fall in phosphate levels. To minimise parathyroid stimulation, one of the active metabolites of vitamin D is given in conjunction with phosphate therapy.
During calcium and phosphate replacement, especially in renal failure patients, there is a high risk for formation of phosphate and calcium complexes. If the calcium-phosphate product exceeds 70 mg²/dL², there is a high risk of metastatic calcification.
Hypercalcaemia may result from vitamin D or calcium over-replacement, especially in the setting of renal impairment. Treatment consists of holding all calcium and vitamin D supplementation until the calcium level has normalised. Aggressive hydration with or without furosemide therapy is required acutely.
High serum calcium levels related to vitamin D or calcium over-replacement can lead to hypercalciuria. Periodic measurement of the 24-hour urinary calcium excretion or the urine calcium:creatinine ratio avoids the risk of hypercalciuria and the complication of kidney stone formation. Calcium and vitamin D supplementation levels are adjusted to maintain the urinary calcium level within the normal range.
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