[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Bones, joints and soft tissue](https://durgical.com/en/general-pathology/areas/bone-soft/) › Rickets and osteomalacia

# Rickets and osteomalacia

- Lesion

Without enough vitamin D or phosphate, new bone matrix cannot harden. Children get bent bones and wide growth plates; adults get soft, painful bones.

Updated Nov 12, 2026

## Key points

- Defect: mineralization of osteoid, from too little vitamin D, calcium or phosphate.
- Rickets: bowed legs, rachitic rosary (swollen costochondral junctions), Harrison groove, craniotabes, frontal bossing, widened wrists, delayed fontanelle closure.
- Osteomalacia: diffuse bone pain, proximal muscle weakness and Looser zones (pseudofractures).
- Vitamin D deficiency: low or normal calcium, low phosphate, high PTH, high alkaline phosphatase.
- X-linked hypophosphatemic rickets (PHEX mutation, high FGF23): phosphate wasting with normal calcium and PTH.
- Biopsy: wide osteoid seams and an increased time between matrix deposition and mineralization.

## What it is

Rickets (in children, before the growth plates close) and osteomalacia (in adults) are failures to mineralize newly made bone matrix. The usual cause is lack of vitamin D from poor sun exposure, diet or malabsorption, kidney or liver disease, but low phosphate states such as X-linked hypophosphatemic rickets and tumour-induced osteomalacia (FGF23 excess) produce the same picture. Excess unmineralized osteoid covers the trabeculae, bone softens and bends, and in children the growth plate becomes a wide, disorganized mass of cartilage.

## Structure

- Trabeculae are covered by thick seams of pale pink unmineralized osteoid on H&E.
- Rickets growth plate: the zone of provisional calcification fails, hypertrophic chondrocytes pile up in irregular, elongated tongues and the metaphysis flares.
- Gross: soft bones bend under weight (bowed legs), the ribs bead at costochondral junctions and the pelvis may deform.
- Looser zones: bands of osteoid crossing the cortex, typically in the pubic rami, femoral neck and scapula.

## Step by step

- Vitamin D comes from skin synthesis and diet and is activated by the liver (25-hydroxylation) and the kidney (1-alpha-hydroxylation).
- Active vitamin D increases intestinal absorption of calcium and phosphate.
- Deficiency lowers calcium and phosphate absorption; low calcium raises PTH.
- PTH keeps calcium near normal but wastes phosphate in the urine, so the calcium-phosphate product falls.
- Osteoblasts still lay down matrix, but it cannot mineralize: osteoid accumulates and bone softens.

## Causes of defective mineralization

| Group | Examples | Laboratory pattern |
| --- | --- | --- |
| [Vitamin D lack](https://durgical.com/en/conditions/rickets-and-osteomalacia/) | Little sun, dark skin at high latitude, exclusive breastfeeding without supplements, diet | Low 25-hydroxyvitamin D, high PTH, high alkaline phosphatase |
| [Malabsorption](https://durgical.com/en/conditions/coeliac-disease/) | Celiac disease, pancreatic insufficiency, bariatric surgery, cholestasis | As vitamin D lack |
| [Organ disease](https://durgical.com/en/conditions/chronic-kidney-disease/) | Chronic kidney disease (no 1-alpha-hydroxylation), liver disease, anticonvulsants | Low calcitriol in kidney disease |
| [Phosphate wasting](https://durgical.com/en/conditions/hypophosphataemia/) | X-linked hypophosphatemic rickets, tumour-induced osteomalacia | Low phosphate, high FGF23, normal calcium |
| Vitamin D-dependent rickets | Defects of 1-alpha-hydroxylase or the vitamin D receptor | Low calcium; calcitriol low or very high |

## Clinical notes

- Toddler with bowed legs, delayed walking, wide wrists and beaded ribs: nutritional rickets until shown otherwise.
- Adult with diffuse bone pain, waddling gait and proximal weakness: think of osteomalacia, especially after bariatric surgery or with malabsorption.
- Severe hypocalcaemia from rickets can cause tetany or seizures in infants.

## Memory aid

Rickets bends, malacia aches: both are bone laid down as soft clay that never fires.

## Test yourself

Think of the answer, then tap the question to see it.

## What is the basic defect in rickets and osteomalacia?

Failure to mineralize newly formed osteoid.

## What is the rachitic rosary?

Bead-like swelling of the costochondral junctions from overgrown, unmineralized cartilage and osteoid.

## What are Looser zones?

Pseudofractures: bands of unmineralized osteoid crossing the cortex in osteomalacia.

## Which hormone is high in X-linked hypophosphatemic rickets?

FGF23, which makes the kidney waste phosphate and lowers calcitriol.

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## Elsewhere in DurgiPedia

- [Vitamin D (calcitriol)](https://durgical.com/en/biochemistry/molecules/vitamin-d/)
- [Calcium and phosphate](https://durgical.com/en/biochemistry/topics/calcium-and-phosphate/)
- [Phosphate and FGF-23](https://durgical.com/en/physiology/phosphate-and-fgf-23/)

## Connections

## Related 4

- [Vitamin deficiencies: what each one does to tissue](https://durgical.com/en/general-pathology/vitamin-deficiencies-what-each-one-does-to-tissue/)
- [Metabolic bone disease compared](https://durgical.com/en/general-pathology/metabolic-bone-disease-compared/)
- [Bone in hyperparathyroidism and renal osteodystrophy](https://durgical.com/en/general-pathology/bone-in-hyperparathyroidism-and-renal-osteodystrophy/)
- [Coeliac disease](https://durgical.com/en/general-pathology/coeliac-disease/)

## Related conditions 4

- [Rickets and osteomalacia](https://durgical.com/en/conditions/rickets-and-osteomalacia/)
- [Hypophosphataemia](https://durgical.com/en/conditions/hypophosphataemia/)
- [Coeliac disease](https://durgical.com/en/conditions/coeliac-disease/)
- [Chronic kidney disease](https://durgical.com/en/conditions/chronic-kidney-disease/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Rickets: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000344.htm) (MedlinePlus, US National Library of Medicine, 2025); [Osteomalacia: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000376.htm) (MedlinePlus, US National Library of Medicine, 2025).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/rickets-and-osteomalacia/