Persistently raised alkaline phosphatase in a woman with osteomalaciaBMJ 2009; 338 doi: https://doi.org/10.1136/bmj.b1874 (Published 03 June 2009) Cite this as: BMJ 2009;338:b1874
- H U Rehman, clinical assistant professor
- 1Department of General Internal Medicine, Regina Qu’Appelle Health Region, Regina, Canada SK S4P 0W5
A 45 year old woman was referred by psychiatrists for assessment of raised alkaline phosphatase. She had been admitted to a psychiatry ward for management of schizophrenia and was being treated with fluphenazine and olanzapine. She had been otherwise well and denied any gastrointestinal symptoms or any bone or muscle pains. Her blood tests results were as follows (normal ranges in brackets)):
Sodium 141 mmol/l (135-145)
Potassium 3.9 mmol/l (3.5-5.0)
Chloride 105 mmol/l (98-110)
Anion gap 13 mmol/l (10-20)
Urea 7.8 mmol/l (3.0-7.1)
Creatinine 121 µmol/l (60-130)
Calcium 2.42 mmol/l (2.14-2.66)
Alkaline phosphatase 239 U/l (40-135)
Alanine transaminases 45 U/l (4-55)
Bilirubin 7 µmol/l (2-20)
Abdominal ultrasound showed normal physiology in the gallbladder, common bile duct, common hepatic duct, and liver parenchyma. Further tests showed that the patient was vitamin D deficient, with a serum level of calcidiol of 23 nmol/l (normal range 25-250 nmol/l). Tests for anti-nuclear and anti-mitochondrial antibodies were negative. Vitamin D2 (ergocalciferol) 5000 units daily and calcium 1500 mg daily were commenced.
Three months later, the patient’s calcidiol level was still only 22 nmol/l. On repeat testing, her alkaline phosphatase concentration had risen to 573 U/l. Vitamin D2 was replaced with calcitriol 0.25 µg daily. Her calcidiol concentration went up to 126 nmol/l and alkaline phosphatase came down to 253 U/l when tested three months later.
Over the next five months, the patient’s alkaline phosphatase concentration ranged from 267 U/l to 279 U/l, despite normal levels of calcidiol (i.e., 165 nmol/l). Given that the patient had no gastrointestinal symptoms, nutritional vitamin D deficiency was thought to be the cause of her vitamin deficiency. However, the biochemical abnormalities did not return to normal after vitamin D replacement. Further investigations were positive for coeliac antibodies (normal values in brackets):
Anti-tissue transglutaminase IgA >200 U/ml (<10)
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