2. Clinical Manifestations

2. Clinical Manifestations

The clinical manifestations of diabetes can be categorized into typical clinical manifestations, atypical clinical manifestations, and the clinical manifestations of complications and/or comorbidities. Many patients, however, exhibit no symptoms at all and are diagnosed with diabetes during routine health check-ups or when seeking treatment for other conditions.

Due to metabolic disturbances caused by diabetes, elevated blood glucose leads to osmotic diuresis, resulting in polyuria, followed by polydipsia and excessive drinking. Impaired glucose utilization causes patients to feel hungry and eat more frequently in an attempt to compensate for the glucose deficiency. Additionally, because of insufficient glucose utilization, the body increases the breakdown of fats and proteins to maintain normal physiological functions, leading to progressive weight loss, fatigue, and, in children, impaired growth and development. Consequently, the classic clinical triad of diabetes is often described as "three polys (polyuria, polydipsia, polyphagia) and one less (weight loss)."

Atypical symptoms include skin itching, particularly vulvar pruritus, abnormal skin sensations, blurred vision, increased susceptibility to infections, and delayed wound healing. In many cases, these atypical symptoms are difficult to distinguish from the manifestations of diabetic complications. Diabetic patients are prone to infectious complications; female patients often develop urinary and reproductive tract infections such as pyelonephritis, cystitis, Bartholin's gland inflammation, and fungal vaginitis. Suppurative skin infections and fungal infections are also common. Pulmonary tuberculosis in diabetic patients often presents as exudative lesions that easily disseminate and form cavities.

Chronic complications of diabetes can affect virtually every tissue and organ in the body, with complex pathogenesis that remains incompletely understood. It is generally believed that these complications result from the interplay of multiple factors. Complications may occur individually or in various combinations, either sequentially or simultaneously. The timing of their onset varies widely: some may already exist before the diagnosis of diabetes, while others may only manifest after prolonged poor disease control. Microvascular complications are specific to diabetes and primarily involve the kidneys, retina, nerves, and myocardium, with diabetic nephropathy and diabetic retinopathy being the most significant. Macrovascular complications, on the other hand, are not characteristic of diabetes; their etiology is highly complex, involving genetic susceptibility, insulin resistance, oxidative stress, and other factors. They are also closely associated with common comorbidities among diabetic patients, such as obesity, hypertension, and dyslipidemia.