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Osteomalacia and Rickets

Title                    

Ñ    Osteomalacia and Rickets

Definition

Ñ    Failure of mineralisation of newly formed bone matrix (osteoid)

Ñ    Structure of the skeleton and its metabolic functions are impaired

Pathogenesis

Causes

Vitamin D deficiency

IS

Ñ    Decreased exposure to sunlight:

Social and cultural reasons

GIT

Ñ    Malabsorption

Ñ    Liver disease:

Impaired conversion to 25 hydroxy vitamin D₃

Drugs

Ñ    Phenytoin

Ñ    Barbiturates

Ñ    Carbamazepine

KUS

Ñ    Renal failure:

Impaired conversion to 1,25 dihydroxy vitamin D₃

E&M

Ñ    Vitamin D resistant rickets type I:

Autosomal recessive

1 alpha hydroxylase deficiency

Ñ    Vitamin D resistant rickets type II:

Defect in intracellular 1, 25-dihydroxy vitamin D₃ receptor

Phosphate deficiency

GIT

Ñ    Malabsorption

Ñ    Ingestion of phosphate binding antacids

KUS

Ñ    Fanconi’s syndrome

Ñ    Renal tubular acidosis

E&M

Ñ    X-linked hypophosphataemic rickets

Tumours

Ñ    Mesenchymal tumours

Calcium deficiency

Ñ    Very rarely causes osteomalacia

Pathological Process

Ñ    Delayed calcification of osteoid

Ñ    Impairment of vascularisation

Ñ    Osteoid width increases

In children:

Ñ    The growth plate is elongated with distorted arrangement of chondrocytes

Ñ    Disruption of orderly replacement of cartilage by osteoid matrix

Ñ    Disordered enchondral bone growth

Ñ    This results in skeletal deformities

Clinical Features

History

CNS

Ñ    Muscle pain

Ñ    Muscle tenderness

Ñ    Weakness

LMS

Ñ    Bone pain

Examination

CNS

Ñ    Weakness

Ñ    Waddling gait

LMS

Ñ    Deformity:

Genu valgum

Genu varum

Rickety rosary

Harrison’s sulcus

Ñ    Fractures:

Rare

Investigations

Fluids

Blood

Biochemistry

Ñ    Alkaline phosphatase:

·          Increased:

Increased osteoblast activity

Ñ    Plasma calcium:

·          Normal:

Due to secondary hyperparathyroidism

·          Low:

Severe cases

Ñ    Serum phosphate:

Low

Ñ    Serum 25 hydroxy vitamin D_3:

·          Low:

Usually

Exception vitamin D resistant rickets

Imaging

X- rays

Ñ    Decreased mineralisation

Ñ    Pseudofractures:

Looser’s zones

Tissue Diagnosis

Bone biopsy with double-labelled tetracycline

Ñ    Widened osteoid seams

Management

Support

Drugs

Ñ    Vitamin D:

Nutritional deficiency

Ñ    25 hydroxy vitamin D₃:

Malabsorption, hepatic disease

Ñ    1,25 dihydroxy vitamin D₃:

Renal disease

Ñ    Phosphate:

Hypophosphataemic disorders

Ñ    Calcium supplementation:

All patients with osteomalacia

Ñ    Vitamin D resistance:

Parenteral calcium and phosphate

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