bubble_chart Overview

Vitamin C (VitC) deficiency can cause scurvy, hence it is also known as ascorbic acid. Ascorbic acid is a hexuronic acid lactone, and the hydrogen in its enol group is easily dissociated, giving it acidic and reducing properties. It is relatively stable in dry or acidic solutions but prone to oxidative degradation and loss of activity when exposed to heat, light, moisture, or the presence of metal ions such as Fe²⁺, Cu²⁺, or in alkaline solutions. Vitamin C is widely found in fruits and leafy vegetables, with particularly high concentrations in sour-tasting fruits like oranges, lemons, hawthorns, and sour jujubes. It is readily absorbed by the intestines and excreted in urine.

The primary functions of vitamin C are to act as a reducing agent and participate in important hydroxylation reactions. When vitamin C is deficient, collagen synthesis is impaired, leading to delayed wound healing, fragile bones prone to fractures, loose teeth, and fragile capillaries that easily rupture and bleed.

Additionally, vitamin C can reduce folic acid to tetrahydrofolic acid, promoting the maturation and proliferation of red blood cells. It also reduces ferric iron (Fe3+) to ferrous iron (Fe2+), enhancing the absorption of dietary iron and the utilization of ferritin. It maintains blood moistening and tonifying activity, converts cholesterol into bile acids, and aids in heavy metal detoxification.

Symptoms of scurvy typically appear after 3 to 4 months of vitamin C deficiency. Infantile scurvy may occur in artificially fed infants who are exclusively fed milk or flour paste for more than six months. Acute or chronic infections, diarrhea, iron deficiency, large-area burns during the stage of convalescence, and severe trauma can all increase the demand for vitamin C, and insufficient supply may lead to deficiency.

Under normal circumstances, a daily intake of 10 mg of vitamin C is sufficient to prevent scurvy. Therefore, except in cases of unusual dietary habits, alcoholism (rare in children), famine, or wartime food shortages, this condition is actually uncommon. The recommended daily dietary allowance of vitamin C is 30 mg for infants and 30–60 mg for children.

bubble_chart Clinical Manifestations

1. Systemic symptoms: such as weakness, anorexia, dysphoria, pallor, growth retardation, intermittent diarrhea, susceptibility to infections, or slow wound healing.
2. Skeletal symptoms: Long bones exhibit significant tenderness due to subperiosteal hemorrhage, most commonly in the tibial shaft of the lower limbs, with possible swelling and mild fever without redness. In the advanced stage, pseudoparalysis may occur due to pain-induced inability to move the lower limbs naturally. The costochondral junctions may present as a beaded appearance, known as scorbutic rosary. This sign results from the separation of ribs and costal cartilage, with the sternum sinking inward (grade I), causing the rib side of the junction to feel sharp-edged. This differs markedly from the symmetrical and smooth beading seen in rickets.
3. Hemorrhagic symptoms: Common bleeding sites include the subperiosteal region of long bones, skin, and mucous membranes such as the gums and conjunctiva. Severe cases may involve hematuria, hematemesis, hematochezia, or meningeal hemorrhage. Orbital hemorrhage can lead to exophthalmos.
4. The advanced stage is often accompanied by anemia, typically microcytic. When folate metabolism is impaired, megaloblastic anemia may occur.

bubble_chart Auxiliary Examination

1. A fasting plasma vitamin C level > 0.6 mg/dl can rule out scurvy. Lower plasma vitamin C levels have limited diagnostic significance, as plasma vitamin C may drop to zero three months before the onset of scurvy.
2. After anticoagulation and centrifugation, the buffy coat containing leukocytes and platelets can be used to measure vitamin C content. If the level is below the normal range (28–30 mg/dl), vitamin C deficiency can be diagnosed. If the content is zero without clinical symptoms, latent scurvy can be diagnosed. Tetracycline may reduce leukocyte vitamin C levels, so this should be excluded.
3. Vitamin C tolerance test: Administer 20 mg/kg of vitamin C intravenously as a 4% solution in physiological saline. If urinary vitamin C excretion exceeds 1.5 mg/dl after 4 hours, scurvy can be ruled out.
4. 24-hour urinary vitamin C excretion <20mg(正常值為20～40mg)可診斷維生素C缺乏。如大量補充維生素C，還待全身飽和後，過剩的維生素C才能經尿排出。
5. If anemia is present, hemoglobin or red blood cell counts may decrease. Elevated plasma tyrosine levels may also be observed in this condition.

Special examinations

1. Capillary fragility test: Positive in overt scurvy.
2. X-ray examination: Changes occur at the junction of cartilage and the diaphysis, with the most actively growing areas affected first. Examples include the sternal ends of ribs, distal femur, proximal humerus, both ends of the tibia and fibula, and distal ulna and radius. X-rays of the knees, ankles, and wrists may show widening of the provisional calcification zone at the metaphysis due to accumulation of calcified cartilage, appearing as a thickened white line. Below this line, there may be a translucent zone of osteopenia, known as the scurvy zone, which may fracture and detach or displace. Additionally, subperiosteal hematoma shadows may be visible, with calcification observed after treatment. The epiphyseal center may show reduced density, surrounded by a denser white line, giving the epiphysis a ring-like appearance. Other findings include thinning of the cortical bone and generalized osteopenia.

bubble_chart Diagnosis

The diagnosis is primarily based on medical history, clinical symptoms, and long bone X-ray examinations, with laboratory tests serving as a reference. The medical history includes insufficient dietary intake of vitamin C, such as infants primarily fed breast milk, cow's milk, or evaporated milk deficient in vitamin C, as well as a history of conditions that increase the demand for vitamin C.

bubble_chart Treatment Measures

The daily dose of vitamin C for infants is 100-300mg, and for children is 300-500mg, divided into 4 oral doses. Intravenous injection can be administered if necessary, with the full daily dose given at once. After 4-5 days, the dose can be gradually reduced to 50-100mg/d until complete recovery. At the same time, provide fruits or vegetables rich in vitamin C, such as orange juice or tomato juice. If anemia is present, the vitamin C dose can be increased, and iron supplements or folic acid may be added as needed.

The treatment effect is remarkable, with appetite improvement and tenderness relief observed within 24-48 hours. Within a few days, lower limb mobility can be restored, tenderness and bleeding disappear, subperiosteal hematomas calcify, and the scorbutic zone is gradually filled with normal trabeculae, forming a dense shadow that merges with the epiphyseal line. Bone structure returns to normal within one year.

bubble_chart Differentiation

1. Limb swelling and pain should be differentiated from infection, pseudoparalysis should be differentiated from poliomyelitis, and bleeding should be differentiated from other hemorrhagic diseases.
2. Differentiation from copper deficiency: Since both copper and vitamin C are essential for collagen synthesis, the same skeletal changes and X-ray features may occur when either is deficient, and differentiation is necessary.