Rickets Diagnosis of Causes Medical Algorithm

Aurbach et al use a series of serum chemistry tests to identify the cause for rickets or osteomalacia in a patient.

Initial tests:

(1) serum calcium

(2) serum parathyroid hormone

(3) serum phosphate

Additional tests that may be required depending on the initial testing results:

(4) serum 25-OH-vitamin D

(5) serum 1,25-(OH)2-vitamin D

(6) serum alkaline phosphatase

Group 1

Serum Phosphate	Serum 25-OH-D	Serum 1,25-(OH)2-D	Diagnosis
high	N/A	N/A	hyperphosphatemic osteomalacia
low	low	N/A	vitamin D deficiency; 25-OH-D deficiency
low	normal	low	deficiency 1,25-(OH)2-D
low	normal	high	target resistance to 1,25-(OH)2-D

Group 2

Serum Phosphate	Serum Alkaline Phosphatase	Diagnosis
low	N/A	phosphate depletion
normal	low	hypo-phosphatasia
normal	normal	abnormal crystal, cell or matrix

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Rickets Diagnosis of Causes