Definition and Overview
Sweating disorders encompass hyperhidrosis (excessive sweating beyond physiological needs) and anhidrosis (absent sweating), both reflecting autonomic nervous system dysfunction. Sweating is controlled by sympathetic cholinergic fibers, and its regulation involves the hypothalamus, limbic system, and peripheral sudomotor pathways [1].
Primary focal hyperhidrosis affects 2.8-4.8% of the population and typically begins in adolescence [1]. It significantly impacts quality of life, causing social embarrassment and functional impairment.
Classification
Primary focal hyperhidrosis: idiopathic, affecting specific areas (palms, soles, axillae, face/scalp). Familial in 30-65% of cases, suggesting genetic predisposition. Onset typically before age 25, bilateral and symmetric, ceasing during sleep [2].
Secondary hyperhidrosis: caused by underlying conditions including endocrine disorders (hyperthyroidism, menopause), neurological conditions (Parkinson's disease, spinal cord injury), infections (tuberculosis, HIV), medications (SSRIs, opioids), and malignancy (lymphoma). Typically generalized and may occur during sleep.
Anhidrosis: absent or reduced sweating, which may be segmental or generalized. Causes include autoimmune autonomic ganglionopathy, Ross syndrome, and pure autonomic failure.
Diagnosis
QSART (Quantitative Sudomotor Axon Reflex Test) evaluates postganglionic sympathetic sudomotor function by measuring sweat output in response to acetylcholine iontophoresis [3].
Thermoregulatory sweat test (TST) maps the entire body's sweat distribution using indicator powder in a heated chamber. Starch-iodine test provides a simple office-based assessment.
For secondary hyperhidrosis, blood tests (thyroid function, glucose, CBC) and imaging as indicated are performed to identify underlying causes.
Treatment
Topical aluminum chloride (20%) is the first-line treatment for mild-to-moderate focal hyperhidrosis. Iontophoresis (tap water) is effective for palmar and plantar hyperhidrosis, requiring 2-3 sessions per week initially [4].
Botulinum toxin injection is highly effective for axillary and palmar hyperhidrosis, with effects lasting 4-12 months. Oral anticholinergics (glycopyrrolate, oxybutynin) provide systemic relief but with dry mouth and other side effects.
Endoscopic thoracic sympathectomy (ETS) is reserved for severe, refractory cases. Compensatory hyperhidrosis in other body areas is a common complication (up to 80%).