NUTRITIONAL RICKETS
Dr Agelebe E.
Bowen University Teach Hosp
Ogbomoso
Calcium
99% of all body Calcium – in bones
Plasma calcium - Free ionized Ca Ω
45%
Protein bound Ca Ω 50%
Diffusible complexes Ω 6.5%
50% of ingested Ca absorbed in jejunum
Ca is filtered in glomerulus
Reabsorption occurs throughout nephron
Calcium
Extracellular ionized calcium concentration within interstitial fluid is the most relevant to calcium homeostatic system.
It is not readily measurable.
Total or ionized serum calcium conc. is therefore determined.
Role of Calcium
Cellular fxns – e.g. muscle contraction, hormonal secretion, cell division
Maintains intercellular adhesions
Promotes plasma membrane integrity
Ensures blood clotting
Ca salts (99%) acts as rigid framework facilitating body movements
Provides reservoir of Ca & PO4 ions for times of need
Phosphorus
85% of body phosphorus is in bones
Only 12% of plasma phosphorus is
protein bound.
70-90% of ingested phosphorus is
reabsorbed at PCT
No tubular secretion of phosphates
Calcium homeostasis
Effective homeostasis dependent on
1) Normal functioning
Parathyroids
Kidneys
Gut - Ca2+ transporting Cells
2) Adequate supply of
Calcium
Vitamin D
Calcium homeostasis
(GUT) Ca absorption
Phosphaturia DCT Ca reabsorption
Ca PTH KIDNEY Vit D3 from Vit D2 Gut Ca & P absorption
Bone resorption
DCT Ca reabsorption (Ca & P release)
Bone resorption (Ca & P release)
PTH secretion
Parathyroid glands
Acts on:
1) Bones: Stimulates osteoclastic
activity and dissolution of bone.
2) Kidneys: ↑ tubular reabsorption
of Ca & ↓ P04 reabsorption
3) Gut : Increases efficiency of
Calcium reabsorption
Calcitonin & Vitamin D3
Calcitonin - Physiological antagonist of
PTH
↓osteoclastic activity & ↓ bone resorption
Increases renal calcium clearance.
Vitamin D3 - calcium absorption from
gut
Along with PTH releases calcium from
bones
Disorders of Calcium Metabolism
Hypercalcaemia
(1) Inappropriate secretion of PTH/PTH-
like substance
10 hyperparathyroidism
30 “
Ectopic production of PTH/PTH- like
substance (Pseudohyperparathyroidism)
Causes of hypercalcaemia
(2) Vitamin D excess - Nutritional
- Granulomatous/Inflam dx
(3) Immobilization
(4) Neoplasia
(5) Others – Hyperproteinemia
- Hypophosphatemia
- Drugs (Thiazides, Vit A)
- Hyperthyroidism
Hypocalcaemia
Neonatal – early, late onset
Hypoparathyroidism - congenital,
acquired
Pseudohypoparathyroidism
Vit D deficiency
Others – Ca deficiency, diuretics, ARF,
CRF, Pancreatitis, malabsorption,
hypoproteinuria
Management of Calcium disorders
Early Neonatal hypocalcaemia - occurs
1st 24-48hrs of life
Give IV 10% Ca gluconate 0.5-1ml/kg
over 15-20mins. Diluted
Late Neonatal hypocalcaemia - Features
are tetany, convulsions etc
same as above for emergency Rx
Change feeds as required.
Neonatal hypercalcaemia
Features are FTT, lethargy, poor feeding,
polyuria, hypotonia, seizures etc
Treatment
IV N/Saline
IV Frusemide - 1mg/kg
Rx underlying disorder
Vitamin D3
Technically, not a true vitamin.
synthesis in skin can provide the body’s entire requirement unless exposure to sunlight is restricted
Few foods naturally contain appreciable amounts of Vit D - livers of fatty fish, cod liver oil, eggs, cheese, butter
Insignificant amounts of Vit D exist naturally in dairy products.
.
Vitamin D synthesis
7 dehydrocholesterol Pre VitD3 VitD3
370C (Liver)
25 hydroxylase
1,25 (OH)2 D3 25(OH)D3
(Kidney)
25(OH) D31αOHlase
Regulation & Biologic action of
Vitamin D
Renal 1α hydroxylation - the most impt
regulatory mechanism – Its activity inversely
proportional to Ca & P ions
- directly proportional to PTH level
Actions are:
Anti-rachitogenic effects – Mobilize Ca & P
Most impt bioeffect is gut absorption of Ca
Consequences of ↓Vit D3
Deficient Calcium absorption
leads to ↓Ca
2o ↑PTH leads to ↑bone
resorption
Prolonged/severe Vit D def
leads to ↓Ca
↓PO4 occur early
Rickets
found primarily in rapidly
growing infants esp preterm
babies
Simultaneous lack of vit D,
sunshine or underlying
pathology of liver, kidneys
Multi-systemic involvement
Causes of Rickets
Nutritional deficiency of vit D & high
dietary phytate
Inadequate exposure to sunlight
Mal-absorption of fat-soluble vits eg
coeliac dx
Inability to absorb from gut
Alteration in metabolism of vit D
Causes of Rickets
Liver dx resulting in malabsorption +failure of 25OHlation
Renal dx resulting in failure of 1α
OHlation
Vit D dependency / Pseudo Vit D deff due to 25OHlase enzyme def
End organ resistance (Vit D resistant rickets)
Drugs that antagonize Vit D action
Anticonvulsant Rx
Pathogenesis
Vit D is essential for new bone formation
Vit D enhances gut absorption of Ca
Vit D Ca from gut plasma Ca
PTH Impaired responsiveness of
bone and gut to PTH & impaired osteoid
maturation size of parathyroid &
kidney response (Ca clearance & P
clearance)
Clinical features
Depends on age and underlying disorder
Preterm may present within 1st 2 mths of life with seizures
Other features are slow growth, bronchopneumonia
In older children -
Craniotabes
Skull bossing
Delayed closure of fontanelles
Chest deformities - Rachitic rosary
Pigeon chest
Harrison’s sulcus
Clinical features
Delayed dentition & defective enamel
Kyphosis, Lordosis, scoliosis etc
Enlarged ankles and wrists epiphyses
Lower limb deformities -
Adduction deformity – Genu valgum (knock
knees)
Abduction deformity – Genu varum (bow legs)
Windswept deformity
Examination
Intermalleolar/Intercondylar distances
Normal 1-2cm
Mild <5cm
Moderate 5-10cm
Severe >10cm
Differential diagnosis of Lower limb
deformity
Genu varum
Idiopathic - Usually bilateral
Physiologic - “
Blounts disease
Retardation of growth plate – medial side
Genu valgum
Idiopathic
Retardation of growth plate – lat. side
Trauma “ “ “ “ “
Paralytic causes – C.P. Polio
Biochemical Investigations
Serum Ca, P, ALP
PTH
Urinalysis for aminoacids
Severe rickets - Ca, P, ALP PTH,
Less severity – NCa, P, ALP, PTH,
Investigations
Xrays of the wrists and ankles
Broadened epiphysis shows a typical
saucer appearance with loss of definition
of the metaphysis
Bone demineralization
Signs are fraying, cupping and widening
of the epiphysis
Treatment
Nutritional Rickets
Vit D 5000 – 10,000units dly x 6-8/52 or
200,000 –600,000units stat (PO)
Ca 500-1000mg dly x 6/52
Ca, P, ALP should be monitored for
evidence of healing
Radiologic healing within 2-4/52
Treatment
Hepatic dx /GIT malabsorption -
25,(OH)D310,000 – 25,000units dly or 300,000units stat or
DHT (dihydrotachysterol) (1mg = 3mg vitD3)
Familial hypophosphataemia -
Vit D (0.5 -1MUnits) + P (1.5 -2g x 4 - 6 doses/day)
or DHT
Treatment
Vitamin D dependent Rickets -
Vit D 10,000units or
DHT
Renal osteodystrophy -
1,25,(OH)2D3. 25000-250,000units/day
or DHT
supplementary Calcium
Treatment
Surgery - Cylindrical P.O.P – 3wkly
Wedge osteotomy before school age -usually 4-5 years
COMPLICATIONS
Cardiovascular and respiratory handicap due to pigeon chest
Contracted pelvis
Bone deformities