Vitamin D deficiency

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Case history #1

A 20-month-old black girl presents with faltering growth and delayed achievement of motor milestones. She seems irritable on examination and is noted to have bowed legs, thick wrists, and dental caries. Her weight and height are below the third percentile for her age. Her diet consists predominantly of breast milk.

Case history #2

A 76-year-old white woman presents with fatigue and severe, unrelenting, aching bone discomfort. She has so far enjoyed good health. However, she currently resides in a home for older people and has minimal exposure to sunlight. On physical examination, minimum pressure applied with the index finger on sternum, radius, and anterior tibia produces wincing bone pain. In addition, she has difficulty getting up from a sitting position, suggesting proximal muscle weakness.

Other presentations

Patients do not typically present with overt clinical signs and symptoms until the deficiency is severe and prolonged. Inherited disorders of vitamin D metabolism and 1,25-dihydroxyvitamin D recognition are rare, and usually present incidentally in the first few months of life with biochemical abnormalities, including hypocalcaemia, secondary hyperparathyroidism, hypophosphataemia, and elevated alkaline phosphatase.[5] Skeletal manifestations (bowing of the legs, growth retardation, bony deformities) become apparent within 12-18 months and are usually severe.[1] Acquired disorders of vitamin D metabolism, such as chronic kidney disease, result in retention of phosphate causing an increase in the production of fibroblast growth factor 23 (FGF-23) by osteocytes. The FGF-23 inhibits the production of 1,25-dihydroxyvitamin D and initially results in secondary hyperparathyroidism.[9] Patients who have a GFR of <30% have a decreased capacity to produce an adequate amount of 1,25-dihydroxyvitamin D3 resulting in secondary hyperparathyroidism.[10] This can cause a metabolic bone disease known as renal osteodystrophy. Patients may be asymptomatic or present with bone and/or joint pain, joint deformation, and fractures.[2]

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