Pathological calcification
Why calcium salts settle in soft tissue: dystrophic calcification in dead or damaged tissue with normal blood calcium, metastatic calcification in normal tissue when calcium or phosphate is high, and what each looks like and does.
By the end, you can
- Explain why soft tissues do not normally calcify, although blood carries plenty of calcium and phosphate.
- Describe how dystrophic calcification starts in dead or damaged tissue and name its common settings.
- Relate the causes of high calcium or phosphate to metastatic calcification and the tissues it favours.
- Describe the gross, microscopic and imaging appearance of calcification, including psammoma bodies.
- Relate calcification of valves, arteries and kidneys to the problems it causes.
- Recognise the classic appearances, stains and tests of pathological calcification, and explain how lowering calcium or phosphate, controlling the parathyroids and replacing a calcified valve act on the mechanism.
What it is
Pathological calcification is the abnormal deposition of calcium salts, mainly calcium phosphate, in soft tissue. Dystrophic calcification occurs in dead or damaged tissue while blood calcium is normal; it is by far the commoner form. Metastatic calcification occurs in normal tissue because blood calcium or phosphate is raised. Calcium stones in ducts and hollow organs are a separate topic.
2 types to tell apart
- Dystrophic calcification
- Local: in necrosis, atheroma, damaged or ageing heart valves, old thrombi and some tumours; blood calcium normal.
- Metastatic calcification
- Systemic: hypercalcaemia or hyperphosphataemia, especially in chronic kidney disease; favours the stomach, kidneys, lungs and blood vessels.
Normal function
Mineral belongs in bone
Bone is hard because crystals of calcium phosphate (hydroxyapatite) are laid down on collagen in its . Osteoblasts control where crystals start, releasing small membrane-bound vesicles that concentrate calcium and phosphate and enzymes that remove local inhibitors.
Blood carries calcium and phosphate at concentrations close to those at which they could precipitate, yet soft tissues stay soft. Inhibitors in blood and tissue, such as pyrophosphate, fetuin-A and matrix Gla protein, stop crystals forming, and healthy cells keep their own calcium very low.
Parathyroid hormone, vitamin D (calcitriol) and the kidneys hold blood calcium in a narrow range, moving calcium between bone, gut and urine and adjusting phosphate excretion. Pathological calcification follows when the local balance tips (damaged tissue) or the systemic one does (high calcium or phosphate).
Underlying change · Step 1 of 4
Dystrophic calcification: dead and damaged tissue
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 2 of 4
Metastatic calcification: too much calcium or phosphate
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 4
What calcification looks like
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 4 of 4
What calcification does
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Exam detail
Exam detail
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Treatment
How treatment works
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .