Definition and Overview
Sweating disorder is a concept that encompasses quantitative and qualitative abnormalities in sweat secretion function. It is divided into hyperhidrosis, in which excessive sweating is secreted, and hypohidrosis/anhidrosis, in which sweating is reduced or absent.
Sweat secretion is achieved by sympathetic cholinergic fibers controlling the eccrine sweat glands. It progresses through the path of sympathetic nerve activation → acetylcholine secretion → sweat gland secretion, and is divided into thermoregulatory sweating and emotional sweating in response to emotional and cognitive stimulation.
Hyperhidrosis
Classification
Primary hyperhidrosis is idiopathic hyperhidrosis that occurs without an organic cause. It occurs in approximately 2.8 to 4.8% of the general population, and it is estimated that approximately 360 million people are affected worldwide. It mainly appears locally in the armpits (axillary region), soles of hands and feet (palpal and plantar regions), face (facial region), and scalp.
Secondary hyperhidrosis appears systemically or locally and is caused by an underlying disease or drug. Causes include infection (tuberculosis), malignant tumor (lymphoma), hyperthyroidism, menopausal hot flushes, acromegaly, autonomic nerve abnormalities, and certain drugs (SSRIs, opioids, etc.).
Symptoms and Effects
It is reported that quality of life is significantly reduced in approximately 75% of patients with primary hyperhidrosis. You may avoid shaking hands, wearing certain clothes, or avoiding social situations. It may interfere with occupational activities (precision work such as medicine, music, art, etc.). Primary hyperhidrosis is mainly caused by emotional stimulation rather than thermal stimulation or exercise, and is characterized by a marked decrease during sleep.
diagnosis
Primary hyperhidrosis is diagnosed when excessive sweating lasts for more than 6 months, occurs bilaterally symmetrically, occurs more than once a week, occurs before the age of 25, has a family history, is lost during sleep, or interferes with daily activities. To rule out secondary hyperhidrosis, evaluation of thyroid function, blood sugar, and systemic symptoms is necessary. At least two of these criteria must be met.
The iodine-starch test (Minor test) is useful for visually identifying sweating areas.
Anhidrosis/Hypohidrosis
Anhidrosis and hypohidrosis are conditions in which the ability to sweat is completely lost or reduced. The ability to regulate body temperature decreases, increasing the risk of heat exhaustion and heat stroke when exposed to high temperature environments.
Causes are divided into central and peripheral. Central lesions include spinal cord injury, multiple system atrophy, Parkinson's disease, and hypothalamic lesions. Peripheral causes include diabetic autonomic complications (distal hypohidrosis), small fiber neuropathy, complex regional pain syndrome, Guillain-Barre syndrome recovery phase, and pure autonomic failure.
Diabetic autonomic complications show a characteristic ‘distal-proximal reversed gradient’ pattern. Damage to the sweat glands in the distal parts (feet, legs) causes anhidrosis, and compensatory hyperhidrosis appears in the proximal parts (trunk, head).
Sweating function test
QSART
Quantitative sweat axon reflex test (QSART) quantitatively measures sweat secretion by stimulating the axon reflex of eccrine sweat glands through acetylcholine iontophoresis. Four areas are measured as standard: forearm, top of foot, ankle, and below the knee. It is sensitive for early diagnosis of small fiber neuropathy and is useful for assessing length-dependent patterns of nerve damage.
Temperature-controlled sweating test (TST)
This is a test that visually records the sweating pattern of the whole body after heat exposure, and is suitable for identifying areas of anhidrosis throughout the body.
treatment
The first line of treatment for primary hyperhidrosis is application of 20% aluminum chloride hexahydrate. Iontophoresis is particularly effective for palmoplantar hyperhidrosis. Botulinum toxin injection has been proven to be effective for about 6 to 12 months for axillary hyperhidrosis, and is also used for palmar and plantar hyperhidrosis.
Oral anticholinergics (glycopyrrolate, oxybutynin) are effective for systemic hyperhidrosis, but have side effects such as dry mouth and dry eyes. Endoscopic thoracic sympathectomy is highly effective in treating palmar hyperhidrosis, but compensatory hyperhidrosis is reported to occur in 80-90% of cases.
Direct treatment for anhidrosis is limited, and treatment of the underlying cause and prevention of exposure to overheating are key.