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