Metastatic Calcification
🪨 Metastatic calcification is the deposition of calcium salts in normal tissues, unlike dystrophic calcification which occurs in damaged tissue.
Commonest causes: 🦴 Hyperparathyroidism, 🫁 Sarcoidosis, 🦠 Malignancy (myeloma, mets), ☀️ Vitamin D excess.
It may also occur in patients with hypermetabolic states and prolonged bed rest.
ℹ️ About
- Deposition of calcium salts in previously normal tissue. 🧬
🧬 Aetiology
- Occurs when the calcium × phosphate product is increased → precipitation of amorphous calcium phosphate in organs, vessels, and soft tissues.
📌 Causes
- ⬆️ PTH (primary or secondary hyperparathyroidism) → hypercalcemia.
- Renal failure (secondary hyperparathyroidism, phosphate retention). 💧
- Malignancy: multiple myeloma, breast Ca, squamous cell Ca (PTHrP). 🎗️
- Vitamin D intoxication or sarcoidosis (↑ calcitriol). ☀️
- Granulomatous disease (TB, histoplasmosis, toxoplasmosis).
- Amyloidosis, Addison’s disease (adrenal calcification).
- Endocrine tumours (e.g. gastrinoma).
- Nephrocalcinosis, ossifying metastases (osteosarcoma, ovarian mets).
🔑 Common Causes (High Yield)
- Hyperparathyroidism: ↑ bone resorption & ↑ renal Ca reabsorption.
- Renal failure: ⬆️ phosphate + secondary HPT → Ca-P imbalance.
- Malignancy: Osteolysis or PTHrP secretion.
- Vitamin D intoxication: ↑ intestinal Ca absorption.
- Granulomatous disease (e.g. sarcoidosis, TB): ↑ calcitriol production.
🧫 Pathology
- Deposits both intracellular & extracellular. 🔬
- Favoured sites: kidneys, lungs (alveolar walls), gastric mucosa, cornea, conjunctiva, arteries (media & intima).
⚙️ Pathophysiology
- Occurs when Ca × phosphate > solubility threshold → Ca salts precipitate.
- Unlike dystrophic calcification, this occurs in absence of tissue injury.
- Favourable environments: alkaline tissues (lungs, kidney, stomach, vessels).
🎯 Commonly Affected Sites
- 🫁 Lungs: Alveolar walls & bronchi → dyspnea, restrictive changes.
- 💧 Kidneys: Tubules/parenchyma → nephrocalcinosis, renal impairment.
- 🍽️ Stomach: Gastric mucosa → gastritis, ↓ acid secretion.
- ❤️ Heart/vessels: Valves, myocardium, arteries → HTN, arrhythmias.
👩⚕️ Clinical Presentation
- Symptoms depend on affected organs + severity.
- 🫁 Dyspnoea, chronic cough, ↓ lung capacity (pulmonary calcification).
- 💧 Polyuria, polydipsia, renal insufficiency (nephrocalcinosis).
- 🍽️ Nausea, vomiting, epigastric pain (stomach calcification).
- ❤️ HTN, arrhythmias, heart failure (cardiac involvement).
🔎 Diagnosis
- 🧪 Bloods: ↑ calcium, phosphate, PTH ± vitamin D abnormalities.
- 🩻 Imaging: X-ray/CT/MRI → tissue calcifications.
- 🔬 Biopsy: Confirms Ca deposits in normal tissue.
- 🧾 Renal function & metabolic workup.
💊 Treatment
- 🎯 Treat underlying cause of hypercalcemia.
- Hydration + loop diuretics (furosemide) to enhance Ca excretion.
- Bisphosphonates & calcitonin to lower Ca. 💉
- Parathyroidectomy if refractory hyperparathyroidism.
- Dialysis in renal failure cases. 💧
- Ongoing monitoring: renal, lung, and cardiac function.
📉 Prognosis
Depends on underlying cause & extent of organ involvement.
🩺 Early recognition + calcium control prevents irreversible organ damage.
