What causes low complement C3 and C4 levels, and what should be done?

Complement C3 and C4 are indicators used to assess immune function and are particularly important in diagnosing certain immune-related diseases. Generally, low levels of complement C3 and C4 may be caused by factors such as aging, excessive exercise, rheumatoid arthritis, acute glomerulonephritis, or hereditary complement deficiency disorders. It is recommended to seek timely medical attention to identify the underlying cause and receive treatment under a physician's guidance. Detailed explanations are as follows:

1. Aging: With advancing age, especially in the elderly, various organ functions gradually decline, including the immune system. The capacity for complement synthesis may decrease, leading to physiological reductions in C3 and C4 levels. Elderly individuals can maintain physical function through appropriate exercise, ensure adequate sleep, maintain a balanced diet, undergo regular health checkups, and monitor changes in complement levels and other indicators.

2. Excessive Exercise: Following high-intensity or prolonged strenuous exercise within a short period, the body may enter a state of stress, which can temporarily affect complement synthesis or increase its consumption, resulting in reduced C3 and C4 levels. It is recommended to schedule exercise intensity and duration appropriately, avoid overexertion, and allow sufficient recovery time after strenuous exercise. Additionally, adequate hydration, electrolyte replacement, and consumption of protein- and carbohydrate-rich foods can aid in recovery.

3. Rheumatoid Arthritis: In this condition, autoimmune attacks on tissues such as the synovial membrane of joints lead to inflammatory responses that consume complement, causing decreased C3 and C4 levels. Patients often present with joint swelling, pain, and deformities. Treatment may follow medical advice to include medications such as prednisone, cyclophosphamide, and methotrexate.

4. Acute Glomerulonephritis: Often caused by streptococcal infection, this condition involves the formation and deposition of immune complexes in the glomeruli, which activate the complement system, leading to significant complement consumption. C3 and C4 levels are typically low, and symptoms often include hematuria, proteinuria, and edema. During the acute phase, bed rest and a low-salt diet are recommended, with close monitoring of disease progression. Treatment may follow medical advice to include medications such as penicillin sodium for injection, losartan potassium hydrochlorothiazide tablets, and furosemide tablets.

5. Hereditary Complement Deficiency: This is a relatively rare condition caused by genetic factors that lead to impaired complement synthesis or structural abnormalities, resulting in persistently low C3 and C4 levels. Patients may experience recurrent infections from an early age. Regular supplementation with exogenous complement, such as fresh frozen plasma, may be necessary, and special attention should be given to preventing infections.

In daily life, it is recommended to consume more protein-rich foods such as lean meats, eggs, and legumes to provide the body with the necessary building blocks for complement synthesis. A varied intake of vegetables and fruits is also advised to obtain adequate vitamins and minerals, which help maintain normal metabolic and immune functions.