Ascorbic acid (vitamin C) is a water soluble vitamin and destroyed by heat.Vitamin C is essential for the formation of normal collagen. Alterations in collagen formation are partly due to failure of incorporate hydroxyproline and praline.
Ascorbic acid has the following functions:
a) Cofactor: Hydroxylation of proline in collagen synthesis, dopamine to adrenaline, tryptophan in serotonin synthesis and the oxidation of tyrosine.
b) Absorption: Enhance the non-haem iron absorption from gut.
c) Metal ion metabolism: It is involved in absorption, mobilization, distribution and intoxication of metal ions.
d) It acts as an antioxidant.
e) Vascular integrity is maintained by antiplatelet and vasodilatory effect (prostacyclin).
The natural sources of ascorbic acid are the citrus fruits, berries, and green vegetables. The RDA is 40mg. Deficiency of vitamin C in the mother's diet may result in scurvy in her breast-fed infant. The need for vitamin C is increased by febrile illnesses, particularly infectious and diarrheal diseases, and by iron deficiency, cold exposure, protein depletion, or smoking.
Formation of collagen and chondroitin sulphate is impaired in case of scurvy. Tendencies to hemorrhage, defective tooth dentin and loosening of the teeth are caused by deficient collagen. Bony trabeculae that have been formed become brittle, periosteum became loosened and subperiosteal hemorrhage occur especially at the end of the femur and tibia.
Etiology:
1. Breast milk contain about 4 to 7 mg/dl of ascorbic acid and is an adequate source of Vit.C, decrease amount of Vit.C in mothers diet results in scurvy in her breast feed baby.
2. In case of febrile illness, infectious and diarrheal disease, iron deficiency anemia, cold expose and protein depletion increase requirement of Vit.C.
Symptoms :
Symptoms are rare at the first 6 months of age. The majority of cases occur in infants 6-25 months of age. Initially there is irritability; tachypnoea, digestive disturbances, and loss of appetite appear. There is tenderness, especially in legs when the infant is picked up or when the diaper is changed. The pain results in pseudoparalvsis, and the lees assume the typical "frog position." in which the hips and knees are semiflexed with the feet rotated outward.
A subperiosteal hemorrhage can be palpated at the end of the femur. The gums become bluish purple and spongy swellings. There may be a "rosary" at the costochondral junctions and a depression of the sternum. The angulation of the "scorbutic beads" is usually sharper than that of the rachitic rosary.
Petechial hemorrhages may occur in the skin and mucous membranes. Hematuria, melena, and orbital or subdural hemorrhages may be found. Anemia may reflect inability to utilize iron or impaired acid metabolism. Wound healing is delayed, swollen joints and follicular hyperkeratosis may develop, as well as the "sicca"syndrome of sjogren, usually associated with collagen disorders and includes xerostomia, keratoconjuctivitis sicca, and enlargement of the salivary glands.
Anemia may be microcytic or megaloblastic. A fasting vitamin C level of the blood plasma over 0.6 mg/dl aids excludes scurvy. In WBC-platelet layer (buffy layer) of centrifuged oxalated blood, a level of zero indicates latent scurvy.
Clinical Manifestation:
Clinical features may occur at any age- majority 6 to 24 months of age. After a variable period of Vit.C depletion- irritability, tachypnea, digestive disturbance and loss of appetite may occur. The legs assume the typical frog position, hip and knees are scmiflexed with the feet rotated outwards (pseudoparalysis) are the most prominent feature. Edematous swelling along the shaft of the leg may be present.
Spongy swelling of the mucus membrane of the gum usually over the upper incisor. Scorbutic rosary may be seen at the costochondral junction with depression of the sternum. The angulalion of the scorbutic beads is usually sharpened due to subluxation of the sternal plate at the costochondral junction. Petechial hemorrhage may be found in skin and mucus membrane. Joints, especially knee joint may be swollen due to intra-articular hemorrhage.
Ascorbic acid deficiency causes impairment of collagen synthesis, so there is defective osteod and dentine (loosening of teeth). There is modification of the intercellular ground substances, which binds the cells of the capillary walls. Therefore, changes in the calcified tissues endochondral bone formation) and capillary hemorrhage (subperiosteal hemorrhage at ends of femur and tibia) and impaired healing of wound.
In severe scurvy, there may be degeneration in skeletal muscles, cardiac hypertrophy, bone marrow depression, and adrenal atrophy. Prothrombin time is greatly increased.
During healing process elevated periosteum (due to subperiosteal haemorrhage) become calcified not affected bone assumes doumble or club shaped. Blood level of Vit.C >.6 mg/dl exclude scurvy.
Treatment
Oral ascorbic acid, 200 mg/day for several weeks. Clinical response occurs rapidly- within 24 to 48 hours. Improvement in radiological picture take a week or two. The administration of three to four ounce of tomato juice or orange juice daily will quickly produce healing. After the starting of treatment subperiosteal haemorrhage may take months to disappear.
The normal daily requirement (35 to 50 mg/day of Vit.C) should be taken after scurvy has been cured. With proper treatment, recovery occurs rapidly but the swelling of subperiosteal hemorrhage may require months.
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