EndocrinologyTier 2Disease (DEADMAN)

Bone metabolism disorders - osteomalacia

Description

Osteomalacia is defective mineralisation of newly formed bone matrix (osteoid), most commonly from vitamin D deficiency - distinct from osteoporosis, where bone mineralisation is normal but bone mass/microarchitecture is reduced

Vitamin D deficiency (the dominant cause) remains common globally, particularly in populations with limited sun exposure, darker skin, malabsorption, or reduced dietary intake, making osteomalacia a clinically relevant differential wherever these risk factors are present

Inadequate vitamin D (or, less commonly, phosphate deficiency/renal phosphate wasting) impairs calcium-phosphate availability for hydroxyapatite crystal deposition into newly formed osteoid, leaving excess unmineralised bone matrix - this explains the characteristic bone pain and, in severe/prolonged cases, pseudofractures (Looser zones) seen on imaging

Biochemistry: low or low-normal 25-hydroxyvitamin D, low-normal or low calcium, low phosphate, and elevated alkaline phosphatase and parathyroid hormone (secondary hyperparathyroidism compensating for reduced calcium absorption) - this biochemical pattern distinguishes osteomalacia from osteoporosis, where routine biochemistry is typically normal
Looser zones (pseudofractures) on plain X-ray are a characteristic, though not universally present, imaging finding

Vitamin D and calcium repletion is generally curative, with bone pain and biochemical abnormalities improving over weeks to months as mineralisation normalises - this reversibility is a key distinguishing feature from osteoporosis, which requires ongoing bone-specific pharmacotherapy rather than resolving with vitamin D repletion alone
Underlying malabsorptive or renal phosphate-wasting causes, where present, require their own specific investigation and management alongside vitamin D/calcium repletion

Vitamin D deficiency (the dominant cause), malabsorption syndromes (coeliac disease, post-bariatric surgery), renal phosphate wasting disorders, secondary hyperparathyroidism (a compensatory biochemical feature)

Osteomalacia's biochemical picture (low calcium/phosphate, elevated alkaline phosphatase and PTH) contrasts with osteoporosis's typically normal routine biochemistry - this distinction is diagnostically important since osteomalacia is often substantially reversible with vitamin D and calcium repletion, while osteoporosis is not similarly reversible with vitamin D alone and requires bone-specific pharmacotherapy

6 more sections, plus exam facts

Premium unlocks every note across every specialty, and the full exam fact library behind it.