History and exam
Key diagnostic factors
common
older age
Vitamin D deficiency is common due to decreased dietary intake, diminished intestinal absorption, and limited exposure to sunlight. Additionally, the skin's capacity for vitamin D synthesis declines with age.[51]
vitamin D and calcium deficient diets
Diets low in calcium- and vitamin D-containing foods and fortified vitamin D-containing foods can lead to calcium and vitamin D deficiency and a subsequent risk of osteomalacia or rickets.
Nutritional rickets is an under-recognised global health problem and can be prevented with adequate vitamin D and calcium intake, as well as vitamin D fortification of foods.[35]
lack of sunlight exposure
In countries of extreme latitude (i.e., northern Europe, China, and North America), cutaneous production of vitamin D virtually ceases in the winter months.[36] Other risk factors for impaired dermal vitamin D synthesis include modest clothing and the use of sunscreens.[37] Confined, older, and/or disabled patients are at high risk.
fractures
Fractures occur with even mild trauma or movement. Any bone may be affected, but long bone fractures are most common, including bilateral femoral neck insufficiency fractures.[52]
malabsorption syndromes
Osteomalacia is especially common in patients with a history of coeliac disease, chronic alcoholism, or chronic pancreatitis.
diffuse bone pain and tenderness
Bone pain is usually localised to the lower extremities, lower spine, ribs, and pelvis, typically at sites of fractures. Fractures may occur with minimal trauma.
proximal muscle weakness
The muscle weakness is characteristically proximal and may be associated with wasting.[30] This can lead to a waddling gait and difficulty climbing stairs.
uncommon
family history of osteomalacia
X-linked hypophosphataemic rickets is inherited as an X-linked dominant genetic disorder. Vitamin D-dependent rickets types 1 and 2 are inherited as autosomal recessive disorders.
waddling gait
Occurs in patients with severe bone pain and proximal myopathy.
Other diagnostic factors
common
uncommon
steatorrhoea
Seen in malabsorption syndromes as fatty, foul-smelling stools.
Risk factors
strong
dietary calcium and vitamin D deficiency
Inadequate calcium intake may be associated with rickets in developing bones. Evidence suggests adequate calcium intake is necessary for optimal skeletal formation in childhood.[31][32]
Malabsorption of vitamin D and calcium is a major cause of osteomalacia in the US. Gastrectomy and coeliac disease account for up to 66% of all cases of osteomalacia related to dietary malabsorption. Osteomalacia occurs in up to one third of patients after a gastrectomy and is highly prevalent following gastric bypass surgery.[19][33]
Occult coeliac disease may present with osteomalacia as its initial presentation.[34]
Vitamin D deficiency related to bariatric surgery is increasingly being recognised.[20][21][22][23]
Nutritional rickets is an under-recognised global health problem and can be prevented with adequate vitamin D and calcium intake, as well as vitamin D fortification of foods.[35]
chronic kidney disease
Phosphate and calcium homeostasis abnormalities and associated hyperparathyroidism occur with chronic renal disease resulting in chronic kidney disease-mineral bone disorder (CKD-MBD) and osteomalacia.
Hyperphosphataemia directly induces hypocalcaemia and decreases the efficacy of 1-alpha-hydroxylase in the kidney, which decreases the levels of the active vitamin D metabolites and thus the ability of the gut to absorb calcium. Subsequently, secondary hyperparathyroidism develops.
limited sunlight exposure
In countries of extreme latitude (i.e., northern Europe, China, and North America), cutaneous production of vitamin D virtually ceases in the winter months.[36]
Other risk factors for impaired dermal vitamin D synthesis include modest clothing and the use of sunscreens.[37] Confined, older, and/or disabled patients are at high risk.
inherited disorders of vitamin D and bone metabolism
Vitamin D-dependent rickets (types 1 and 2) are rare inborn errors of vitamin D metabolism that occur despite adequate vitamin D intake. X-linked hypophosphataemic rickets, the most common form of hereditary rickets, is a disorder of renal phosphate wasting that predisposes to the development of osteomalacia.
hypophosphatasia
Hypophosphatasia is associated with the development of osteomalacia and severe periodontal disease.[4]
Hypophosphatasia is a rare inborn error of metabolism characterised by subnormal activity of tissue-non-specific isoenzyme of alkaline phosphatase.
anticonvulsant therapy
The development of rickets and osteomalacia is more common in patients on anticonvulsant therapy with limited exposure to sunlight, such as those who are institutionalised or disabled. In these patients, the prevalence has been reported to be as high as 60%.[1]
Anticonvulsants both increase the catabolism of vitamin D and reduce intestinal calcium absorption. Common culprits include phenobarbitone, phenytoin, and carbamazepine.[38] In addition, phenytoin has been shown to increase bone resorption.
weak
mesenchymal tumours
Acquired mesenchymal tumours may cause a tumour-induced osteomalacia, also known as oncogenic osteomalacia or tumour-induced osteomalacia, with renal phosphate wasting.[39]
Fanconi's syndrome
The use of protease inhibitors, for the treatment of both HIV and hepatitis B, is associated with the development of Fanconi's syndrome and subsequent osteomalacia.[40][41] Valproate-induced Fanconi's syndrome has also been described.[6][7]
Fanconi's syndrome results from a generalised impairment in renal proximal tubular function, leading to urinary wasting of compounds normally reabsorbed in the proximal tubule. The consequences are hypophosphataemia (which can lead to osteomalacia), glucosuria, hypouricaemia, aminoaciduria, and type 2 renal tubular acidosis due to bicarbonate loss in the urine.[42]
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