From the Guidelines
A workup for a patient who reports inability to sweat (anhidrosis) should begin with a thorough history and physical examination, focusing on determining whether the condition is generalized or localized, congenital or acquired, and utilizing diagnostic tests such as thermoregulatory sweat testing and quantitative sudomotor axon reflex test (QSART) to assess sweat gland function and autonomic nerve function, as recommended by the most recent study 1. The evaluation should include key history elements such as onset, progression, associated symptoms, medical conditions, medication use, and family history.
- Physical examination should assess skin moisture, temperature regulation, and neurological function.
- Diagnostic testing may include:
- Starch-iodine test to visualize sweat patterns
- Thermoregulatory sweat test to assess sweat gland function
- QSART to evaluate autonomic nerve function
- Skin biopsy to examine sweat gland structure
- Blood tests to check for underlying conditions like diabetes or thyroid disorders
- Autonomic function tests
- Imaging studies such as MRI may be indicated if neurological causes are suspected, as suggested by the study 1. The study 1 highlights the importance of assessing small fiber neuropathy, which is strongly associated with anhidrosis, and can be evaluated through tests of sweating, including thermoregulatory sweat testing and QSART.
- Treatment depends on identifying and addressing the underlying cause, which could range from medication side effects to neurological disorders, skin conditions, or genetic abnormalities.
- Anhidrosis is important to diagnose and treat as it can lead to heat intolerance, hyperthermia, and potentially life-threatening heat stroke, particularly in hot environments or during physical exertion, as noted in the study 1. While other studies, such as 1 and 1, provide information on sweat testing and diagnosis of conditions like cystic fibrosis, the most recent and relevant study for anhidrosis workup is 1, which guides the recommendation for diagnostic testing and evaluation.
From the Research
Diagnosis of Anhidrosis
The diagnosis of anhidrosis involves a comprehensive workup to determine the underlying cause of the condition.
- The workup may include a thorough medical history and physical examination to identify any underlying autonomic disorders 2, 3.
- Autonomic function tests, such as the thermoregulatory sweat test, quantitative sudomotor axon reflex test, and heart rate response to deep breathing, can be used to evaluate the severity and distribution of autonomic failure 4.
- A starch-iodine sweat test can be used to confirm the diagnosis of anhidrosis and to distinguish it from other conditions, such as hyperhidrosis 5.
- Laboratory tests, such as serum immunoglobulin E, complete blood cell count, thyroid function test, and antinuclear antibody levels, may be ordered to rule out other underlying conditions 5.
Clinical Applications
Autonomic function tests have several clinical applications, including:
- Defining the presence and severity of autonomic failure 4
- Evaluating the response to treatment 4
- Diagnosing certain autonomic conditions, such as autonomic neuropathies and distal small fiber neuropathy 4
- Distinguishing between different synucleinopathies, such as Parkinson's disease and multiple system atrophy 4
Types of Anhidrosis
There are different types of anhidrosis, including:
- Primary anhidrosis, which is a benign condition that tends to have a significant impact on quality of life 2
- Secondary anhidrosis, which is caused by underlying diseases or medications 6
- Acquired idiopathic anhidrosis, which is a rare condition characterized by anhidrosis in the absence of any neurologic or sweat gland abnormalities 5