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Nursing Field Notes / Musculoskeletal · Med-Surg Course

Osteomalacia & Rickets 🦴

Soft bone · Vitamin D · The one that is not osteoporosis

NG-389 Musculoskeletal ADHD-friendly visual edition

Osteomalacia is softening of bone: the amount of bone is normal, but it is poorly mineralised. In a child, whose growth plates are still open, the same problem is called rickets and bends the legs. Osteoporosis is too little bone; osteomalacia is enough bone, badly made.

The causeVitamin D deficiency — diet, sun, malabsorption or renal disease
Adults vs childrenOsteomalacia in adults · rickets in children
The labsLow vit D, low Ca, low phosphate, HIGH PTH, HIGH alk phos
Not the same asOsteoporosis — that one has normal labs and a low DEXA

🧨 What starts it

Lecture slide on osteomalacia describing softening of the bones from impaired bone metabolism and reduced mineralisation, known as rickets in children, with causes of vitamin D deficiency and renal disease, signs of lower back pain, pelvic pain and hip pain, and a comparison of normal bone with rachitic bone including bowed legs.
From your lecture. Note the bowed legs and the widened growth plate in the rickets column — that is what soft bone does when a child is still growing and weight-bearing.
Where the vitamin D goes missing
  • Not enough sun, dark skin, covered skin, northern latitude, housebound.
  • Malabsorption — celiac disease, Crohn’s, bariatric surgery, chronic pancreatitis.
  • Renal disease — the kidney does the final activation step, so failure means no active vitamin D.
  • Liver disease, and drugs that speed vitamin D breakdown (phenytoin, carbamazepine).
The mechanism in one line

No vitamin D → no calcium absorbed from the gut → serum calcium falls → PTH rises to defend it → PTH pulls calcium out of bone and dumps phosphate in the urine. The bone ends up soft.

Why PTH is the giveaway

A high PTH with a low calcium is the fingerprint. In osteoporosis these are all normal.

🔎 What you will see

What she reports
  • Lower back, pelvic and hip pain — a deep, aching bone pain, worse on weight-bearing.
  • Muscle weakness, especially the hips — trouble rising from a chair or climbing stairs, and a waddling gait.
  • Pathologic fracture, and pseudofractures (Looser zones) on X-ray.
In a child (rickets)
  • Bowed legs once they start to walk.
  • Widened wrists and ankles, rachitic rosary along the ribs.
  • Delayed fontanelle closure, delayed teeth, short stature.
The labs, together

Low vitamin D · low calcium · low phosphate · high PTH · high alkaline phosphatase. Alk phos is high because the bone is frantically trying to build.

🩺 What you do

Treatment
  • Vitamin D replacement is the center of it, with calcium and sometimes phosphate.
  • In renal failure use the activated form (calcitriol) — the failing kidney cannot activate the ordinary one.
  • Sensible sun exposure, and fortified foods, oily fish, egg yolk.
  • Treat the cause — the celiac disease, the malabsorption, the renal failure.
  • Safety: this bone breaks easily. Fall precautions until it remineralises.
Tell them apart

Osteoporosis: normal labs, diagnosed on DEXA, treated with bisphosphonates.
Osteomalacia: abnormal labs, diagnosed on bloods, treated with vitamin D.

Expect it to be slow

Pain improves over weeks; the bone takes months. Keep taking it after she feels better.

⚡ Quick recall

The causeVitamin D deficiency — diet, sun, malabsorption or renal disease
Adults vs childrenOsteomalacia in adults · rickets in children
The labsLow vit D, low Ca, low phosphate, HIGH PTH, HIGH alk phos
Not the same asOsteoporosis — that one has normal labs and a low DEXA
Osteoporosis or osteomalacia — which has abnormal labs?
Osteomalacia. Osteoporosis has a normal calcium, phosphate and PTH, and an abnormal DEXA.
Why is PTH high?
The low calcium drives it up. It is the body defending the serum calcium at the expense of the bone.
Which vitamin D form in renal failure?
The activated one, calcitriol — the kidney cannot do the last step.
What does it look like in a child?
Rickets: bowed legs, widened wrists and ankles, rachitic rosary.