Non Nutritional Rickets

Rickets

Softening of bones because of defective mineralization of osteoid.

This may be due to lack of Calcium, Phosphorus, Vitamin D

Sources of Vit D :

Formation of Vit D from the skin 7 dehydro cholesterol is present in the skin layers. UV rays convert it to Vit D3 (Cholecalciferol)

Dietary intake of either vitamin D2 (ergocalciferol) or vitamin D3

Metabolism of Vit D

The primary absorption site for vitamin D is the jejunum.

First metabilosm in liver by 25 hydroxylase enzyme to form 25 OH Vit D

Second metabolism in Kidney by 1 alfa hydroxylase enzyme to form 1,25 Di Hydroxy Vit D Which is the Active form of Vit D

Actions of Vit D

Its major role is to maintain Serum calcium. It promotes

Absorption of Calcium and Phosphorus from food in the intestines

Reabsorption of calcium in the kidneys

Enabling normal mineralization of bone

Lack of Vit D

Decreases Mineralization of newly formed bone matrix (Osteoid)

Decreases rate of bone formation

Net result is less total bone & marked change in quality of bone

Clinical features of rickets

Craniotabes

Delayed closure of anterior fontanelle

Frontoparietal bossing

Delay in teeth eruption, enamel hypoplasia

Rachitic rosary

Harrison sulci

Violin case deformity of the chest

Enlargement of wrists

Progressive bowing of long bones

Delayed motor milestones

Hypotonia

Myopathy with normal deep tendon reflexes, and Propensity for infections (as a consequence of impaired phagocytosis and neutrophil motility)

Non Nutritional Rickets

Not due to Nutritional deficiency

Growth Failure

May not respond to Arachitol injections

Repeated doses of Arachitol may contribute to to hypercalciuria & nephrocalcinosis

When to suspect non nutritional rickets

If child with Rickets shows

Failure to thrive

Dehydration

Constipation

Therapy resistance

Family History of rickets

Clinical Approach to child with non nutritional rickets

Proper History- polyuria, polydipsia, constipation, steatorrhea, drugs, FH

Check All records available of Weight, Height

H/O treatment taken so far including calcium supplements & Vit D taken in any form

Look for Acidotic breathing

Measure inter malleolar distance

Investigations

CBC

S.Ca/ PO4/ Alk Phos

S.Albumin/ SGPT

S.Creatinine

S.HCO3/ VBG

S.Electrolytes

 

 

Rickets develops due to Lack of Vit D

Nutritional deficiency - Congenital Rickets

Malabsorption of fat soluble vitamins

DLiver disease or increased metabolism of Vit D due to anticonvulsants or other drugs

Chronic renal insufficiency

Vitamin D dependent rickets – genetic cause for deficiency of Active Vit D or end organ resistance to action of Active Vit D

Rickets also develops due to Phosphaturic states

Hypophosphatemic rickets - PHEX gene mutation. X linked disease The change created in the gene is a loss-of-function mutation and results in reduced breakdown of a substance known as fibroblast growth factor (FGF23). FGF23 acts on the kidney to cause increased phosphate excretion and decreased alpha-1 hydroxylase activity.

Oncogenic rickets - Secretion of FGF 23 by mesenchymal tumor

Renal Tubular Acidosis

Decreased renal synthesis of Active Vit D ,

Decreased Ca absorption, Hypocalcaemia,

Increased PTH which leads to phosphaturia & hypophosphatemia

Bone alkali mobilized to neutralize acids

Other possibilities

Hypophosphatasia Tissue non-specific alkaline phosphatase (TNSALP) deficiency in osteoblasts and chondrocytes impairs bone mineralization, leading to rickets or osteomalacia. The pathognomonic finding is subnormal serum activity of the TNSALP enzyme

Metaphyseal dysplasia It is characterized by defect in metaphyseal remodeling that leads to grossly widened metaphyses of long bones with marked cortical thinning and osteoporosis (Erlenmeyer-flask deformity) especially in the distal end of femur and proximal tibia.

Maccune Albright Syndrome - Polyostotic fibrous dysplasia , Cafe Au Lait Spots & Precocious puberty

Fluorosis

Nutritional Rickets

Common in Actively growing children

Their need is more :Active growth, Less supply of nutrients

No other systemic disease or dysfunction

Common problem in the community can be prevented by food fortification (milk)

Tests on Urine

Urine routine: PH, specific gravity, Pus cells

Urinary Na, K, Cl, HCO3

U.Calcium, PO4

U.Creatinine

Radiological investigations

X ray of Wrist/ Knee

X ray chest

USG Abdomen: Liver- Size, Echogenicity, fatty infiltration, KUB- stones, nephrocalcinosis

Lab Approach to a child with non nutritional rickets

Look at S.Calcium, PO4 & Alk phos

Confirm diagnosis of rickets

Look at SGPT, S.HCO3 & S.Creat

Whether liver disease, Acidosis &/Or renal failure

IF SGPT, S.HCO3 & S.Creat Normal

Possibility of Hypophosphatemia
( Low PO4, Normal S.Ca & PTH)

Vit D dependent rickets
Low or normal PO4, Low S.Ca, High PTH)

Distal RTA suspected as

Failure to thrive

Hyperchloremic Normal anion gap Metabolic Acidosis

Positive urinary Anion Gap

Normal 25 OH Vit D level

Urinary bicarb undetected