Rickets and Osteomalacia Flashcards
Rickets and Osteomalacia define:
Rickets and Osteomalacia are the conditions that develop when people are Vitamin D deficient
Rickets = children Osteomalacia = adults
Main Function of Vitamin D?
- ↑ed intestinal Ca2+ absorption
- bone formation
- bone mineralisation
- bone remodelling stimulated
- ↓ed renal loss of Ca2+
- Ca2+ mobilisation from bone
Difference between Rickets and Osteomalacia?
-Children’s bones are still growing, thus vitamin D deficiency manifests differently in children.
Vitamin D Synthesis:
When 7-dehydroxycholesterol within the skin is exposed to UV-B light from the sun it synthesizes into previtamin D3. As a fat-soluble vitamin, dietary vitamin D is incorporated into chylomicrons and transported via lymphatics into the venous circulation. Some of the dietary vitamin D is extracted by adipose tissue and muscle, but the remainder and most of the endogenously synthesised vitamin D is transported to the liver. At the liver it is metabolised by enzymes vitamin D 25-hydroxylases (hydroxylation) into 25-hydroxy vitamin D. This is then converted into the biologically active form of vitamin D (1, 25- dihydroxyl-vitamin D3 in the proximal tubule of the kidney.
Rickets and osteomalacia classification:
- Vitamin D deficiency
- ↓ed 25 (OH) D3 synthesis
- ↓ed 1, 25 (OH)2 D3 synthesis
- Defective action of 1,25(OH)2 D3
- Other e.g. Familial renal tubular defects etc
Rickets and osteomalacia classification Vitamin D Deficiency:
- dietary lack
- increased intake of phytates
- increased phosphate intake
- decreased exposure to sunlight
- malabsorption syndromes
Rickets and osteomalacia classification, ↓ed 25 (OH) D3 synthesis:
- liver disease
2. drugs which affect liver metabolism
Rickets and osteomalacia classification, Defective action of 1,25(OH)2 D3:
ie the hormone is either:
i. abnormal : vitamin D administration is curative ii. absent/defective: vitamin D receptors (ie vitamin D independent) administration of vitamin D is not curative.
Rickets and osteomalacia classification, Other
eg. familial renal tubular defect
Rickets pathological manifestation
- Defective calcification of growing bone
- Hypertrophy of epiphyseal cartilage
- Cessation of diaphyseal calcification
- Bone resorption in diaphyses
Fontanel closure:
- The posterior fontanelle generally closes2to3months after birth;
- The sphenoidal fontanelle is the next to closearound 6 monthsafter birth;
- The mastoid fontanelle closes next from6to18 monthsafter birth
- The anterior fontanelle is generally the last to close between18–24 months.
Rickets in neonates SSX:
- Restless
- Poor sleep
- Decreased skull mineralisation (craniotabes)
Craniotabes
is softening or thinning of the skull in infants and children, which may be normally present in newborns. It is seen mostly in the occipital and parietal bones. The bones are soft, and when pressure is applied they will collapse underneath it.
Rickets in Older infants:
- Delayed sitting/crawling
- Bossing (rounded eminence) of skull bones
- Costochondral beading (rachitic rosary)
- Delayed fontanelle closure
Frontal Bossing:
Definition: abnormal prominence of the forehead
Bossing in rickets is due to the premature closure of the anterior portion of the sagittal suture, resulting in compensatory expansion of the frontal diploe
•A build up of excess of osteoid is also thought to add to the thickening of the frontal bone
Rachtic Rosary / Costochondral veading
The prominent knobs of bone at the costochondral joints of rickets patients are known as a rachitic rosary or beading of the ribs
Rickets Wrist enlargement?
Long bones, laying down of uncalcified osteoid below the growth plate leads to metaphysial enlargment & spreading
This results in a knobby deformity, which is seen on xray as metaphysial cupping & flaring
The expansion of the growth cartilage contributes to the clinical deformity
Rickets in 1-4 year olds
- Enlargement of epiphyseal cartilages at the distal end of: the radius, ulna, tibia and fibula
- Kyphoscoliosis (vertebral softening)
- Bowleg
- Delayed walking
Rickets >4
- Pain on walking
- Bowlegs
- Knock-knees
Rachitic tetany?
-vitamin D in calcium homeostasis is to increase calcium absorption from the intestine. An abnormal condition characterized by periodic painful muscular spasms and tremors, caused by faulty calcium metabolism
Rickets Radiological Findings
- Precede clinical signs
- Occur in 3rd -4th month of life
Rickets Radiological Observations:
- Metaphysial cupping & flaring: normal forces acting on weak bone, metaphysis is attached to an abnormally widened/enlarged epiphysial growth plate.
- Spotty Rarefaction (reduced density) at diaphyseal ends: Cessation of diaphyseal calcification, Bone resorption in diaphyses
- Distance between the end of radius and metacarpal bones seems increased because the bone ends are not mineralised: Defective calcification of growing bone, hypertrophy of cartilage
- Bending bones: Uncalcified osteoid of growing bones coupled with pressure from gravity and upper body causing bending causing bowed legs
Osteomalacia Radiological observations:
- Demineralisation especially in: spine pelvis and lower extremities (pseudo-Fruactures, incomplete ribbon-like demineralisation of the cortex)
- Bone softening results in : Bowling of long bones, vertical shortening of vertebrae, flattening of pelvic bones
- Kyphosis
Laboratory Findings of osteomalacia low:
25 (OH)D3: Extremely low 1,25 (OH)2D3: Extremely low Phosphate: Low Alkaline Phosphatase: increased CA2+: Decreased - normal PTH: Increased Urinary CA2+: Decreased
