Anhidrosis

What is Anhidrosis?

Anhidrosis is the medical term for not being able to sweat. It’s important to recognize this condition as it can be dangerous, possibly leading to heat-related illnesses. Anhidrosis can be caused by three main factors: changes in the sweat glands, an unknown cause (termed ‘idiopathic’), or diseases, medications, and issues that affect the nervous system’s communication to the sweat glands.

The nervous system could be disrupted at any point along its path to cause anhidrosis. It could be in the part of the brain that controls sweating, the path that the nerve signal takes, or at the sweat gland itself. Notably, certain conditions like tumors or blood clots in the brain or spinal cord, spinal cord injuries, genetic conditions like Shy-Drager syndrome, autoimmunity affecting nerves, nerve damage from diabetes or alcoholism, leprosy, and certain medications can all result in this kind of disruption.

Changes that occur directly in the sweat glands can also lead to anhidrosis. These can be present from birth or develop over time. Genetic abnormalities such as incontinentia pigmenti, local damage from something like a tumor, or blockages from conditions like psoriasis can all lead to this kind of alteration.

Since several different health problems could be the underlying cause of heat intolerance, a detailed history of symptoms is crucial for making the right diagnosis. Symptoms such as tiredness, focus problems when in hot environments, and reduced normal sweating can all hint towards anhidrosis. The history should also include any recent changes in medication, medical events like injuries, tumors, or exposure to radiation, alcohol use, any autoimmune diseases or diabetes, and family medical history.

What Causes Anhidrosis?

Anhidrosis, or lack of sweating, can be caused by problems in any part of our body’s nervous system. Different signs can help doctors figure out where the problem is. For example, if the patient feels no sweat on one side of their face or neck, the issue is likely in a specific part of their brain.

Our spinal cord contains coated and uncoated fibers. Depending on where a problem is in the spinal cord, a person might sweat less on either the same side or the opposite side of where the problem is. Conditions like diabetes or alcohol disorder can cause nerve issues that lead to even sweating across the body. But, in some cases like leprosy, the lack of sweating can affect just one side of the body. If a condition called Horner syndrome happens due to a problem in a nerve group in the neck, this can also cause lack of sweating in certain areas.

Sweating can also be affected or blocked by specific chemicals that act on parts of the nervous system. Widespread lack of sweating can happen due to some rare inherited conditions. In some of these conditions, people can feel no pain, have intellectual disabilities, may harm themselves, and have recurrent fever.

There are certain drugs that can lead to anhidrosis, such as drugs that interfere with the communication in nerve groups, calcium channel blockers, alpha-adrenergic blockers like phentolamine, alpha2-adrenergic agonists like clonidine, 5-fluorouracil, topiramate, zonisamide and quinacrine.

Problems with the sweat glands can also cause anhidrosis. Several inherited and systemic diseases can either result in generalized or localized anhidrosis. For instance, men with a certain genetic condition can have no sweat glands at all, while women carriers may sweat less than normal. Other inherited conditions, including some extremely rare syndromes, may result in sweat gland dysfunction.

Acquired anhidrosis (anhidrosis that’s not inherited), on the other hand, can be caused by damage to the skin tissues. This damage can be from tumours, radiation therapy, burns and different diseases, which can distort the normal skin structure and lead to anhidrosis. Skin conditions that block the sweat glands, such as psoriasis, eczematous dermatoses, porokeratosis and bullous diseases, can also lead to anhidrosis.

Risk Factors and Frequency for Anhidrosis

Anhidrosis, a condition where there’s a lack or absence of sweat, is not a disease itself, but a symptom of other underlying conditions. Men and women are generally affected equally, and the age at which it appears can differ, depending on what’s causing it. Here are some conditions that can result in anhidrosis:

• Horner syndrome, a rare disorder, can lead to anhidrosis and affects roughly 1 in every 6,000 people. It can occur in any age group or ethnicity.
• Hypohidrotic ectodermal dysplasia is another cause. Patients either have a scarcity of sweat glands or have undeveloped ones. In the US, there’s about 1 case for every 100,000 babies born. Globally, around 7 in 10,000 babies are affected.
• Naegeli-Franceschetti-Jadassohn (NFJ) syndrome is a very rare cause of anhidrosis, with about one case in every 2 to 4 million people.
• Fabry disease, which also results in a lack of sweat glands, affects roughly 1 in 40,000 people.

There are many other disorders that come with anhidrosis and have variable incidences.

Signs and Symptoms of Anhidrosis

Anhidrosis is a condition where a person is unable to sweat normally, and it can have various causes. If you are a healthcare professional trying to diagnose this condition, understanding the patient’s medical history is important. This includes their past medical issues, any medication they’re taking, treatments like radiation therapy, and their family health history. Carefully noting these details can help identify the cause of anhidrosis.

Patients with anhidrosis often report being unable to tolerate heat, feeling tired, experiencing sleepiness, and having difficulty concentrating in warm settings. Additional symptoms may be present, depending on the cause. For instance, if anhidrosis is related to nerve issues (neuropathic anhidrosis), the patient might also have droopy eyelids (ptosis) and a smaller pupil in one eye (miosis), as seen in Horner syndrome. In rare cases, patients with a condition called congenital insensitivity to pain with anhidrosis might exhibit self-harm.

The physical examination for anhidrosis will also depend on its underlying cause. If anhidrosis is caused by tissue damage, there may be visible signs of the cause, like scars from previous burns or changes in the skin’s texture relating to morphea. If the condition is caused by an obstruction, signs related to that problem should be visible, such as psoriasis or lamellar ichthyosis.

Testing for Anhidrosis

If your doctor suspects that you have a problem causing you to sweat less than normal, they’ll start by asking you about your medical history. This will help them determine the possible reasons behind your condition. They may also check whether you’re taking any medications that might be contributing to your symptoms.

There are a few tests they might perform to verify your condition. One test involves changing the color of your skin or measuring its weight to indicate the amount of sweat you’re producing. They might inject a small amount of a special drug into your skin to see if this makes you sweat. This is safe, but they’ll only do it on a small area of skin because it can sometimes have side effects.

If your doctor thinks you might have damage to the peripheral nerves in your body, they might do a test called an axon reflex sweat test. This involves injecting a substance like nicotine sulfate into your skin and then checking how much you sweat.

Your doctor might also do a skin biopsy, which involves removing a small piece of skin from an affected area for examination under a microscope. This helps determine if there are abnormalities in your sweat glands.

A quantitative sudomotor axon reflex test (QSART) is another test your doctor may perform. They’ll place electrodes on your skin and apply a mild electrical stimulation. This electric stimulation allows a chemical called acetylcholine to enter your skin which results in your sweat glands producing sweat. The amount of sweat you produce can then be measured. This test aims to analyze the functioning of the nerves that control sweating in your body.

There’s another test called the Silastic sweat imprint test. Similar to QSART, it involves using electrodes. However, in this case, a substance called pilocarpine is used to stimulate the sweat glands. The droplets of sweat that form make imprints on a specially-prepared silicone rubber sheet. This allows your doctor to visualize and measure your sweating pattern.

Last but not least, your doctor might conduct a thermoregulatory sweat test. This is a test where they heat up your body to a level that should naturally make you sweat and then observe your sweating responses. This test is basically used to see how well your body’s internal thermostat is working with relation to producing sweat.

Treatment Options for Anhidrosis

Treatment options for anhidrosis, a condition where your body can’t sweat normally, can sometimes be limited, especially if it’s not possible to stop using a medication that may be causing the problem. It’s critical for people with this condition to stay in a cool environment. Using water spray bottles can help keep the body cool. If the condition is due to blocked sweat glands, frequently and gently exfoliating the skin can be helpful.

For conditions where the skin thickens and overheats, like lamellar ichthyosis, treatment should be started early and closely monitored.

Although there’s no strong scientific evidence to confirm it, some individual reports suggest that using steroid medications could help if started in the early stages of some specific types of anhidrosis. However, these might not be helpful if treatment is delayed or if sweat gland destruction has happened.

The key to treating anhidrosis is addressing the root cause of the condition. For example, if a type of lung cancer (lung carcinoma) is causing a condition called Horner syndrome, which in turn is leading to anhidrosis, then the lung cancer must be treated.

What else can Anhidrosis be?

When examining a patient for anhidrosis (inability to sweat normally), doctors need to consider a variety of causes. These can be grouped into three main categories: central or neuropathic anhidrosis, medications, and issues with sweat glands.

Central or Neuropathic Anhidrosis: This involves issues with the nervous system and might include:

• Certain tumors or issues with parts of the brain or spinal cord
• Horner syndrome
• Conditions like Ross syndrome or Shy-Drager syndrome
• Autoimmune neuropathy
• Genetic conditions that cause inability to feel pain and lack of sweating
• Nerve damage due to conditions like diabetes, alcoholism, or leprosy

Medications: Certain drugs can also cause anhidrosis, including:

• Drugs that block certain receptors, like hexamethonium, trimethaphan, or atropine
• Medications that affect calcium channels
• Drugs that block or stimulate alpha-adrenergic receptors, like phentolamine or clonidine
• Certain cancer treatments and other medications like 5-fluorouracil, topiramate, zonisamide, and quinacrine

Peripheral Causes Due to Sweat Gland Abnormalities: Issues with the sweat glands themselves can also cause anhidrosis. These can include:

• Genetic disorders such as certain types of ectodermal dysplasias, incontinentia pigmenti, Bazex-Dupré-Christol syndrome, or Fabry disease
• Damage from tumors, burns, radiation therapy, autoimmune conditions like Sjögren syndrome, or issues related to certain skin diseases
• Obstructions caused by certain skin conditions like miliaria, ichthyoses, psoriasis, eczema, or bullous diseases

What to expect with Anhidrosis

The future outcomes or prognosis of anhidrosis (a condition that prevents your body from sweating normally) can change, depending on the type of anhidrosis you have. If your anhidrosis is connected to a genetic syndrome, you’ll likely have it for life. If it’s caused by a certain medication you’re taking, it can typically be reversed once you stop taking that medication. If your anhidrosis is due to a condition that can be treated, then it’s generally reversible and you can expect a good outcome or prognosis.

Possible Complications When Diagnosed with Anhidrosis

The health problems linked to anhidrosis largely depend on its cause. The most serious issues usually relate to overheating in the body, such as heat-related illnesses. Kids are more at risk because their body temperature can increase more rapidly than adults, and their bodies don’t cool down as effectively. Among heat-related illnesses are:

• Heat cramps
• Heat exhaustion
• Heatstroke

The most dangerous complication, regardless of the specific cause of anhidrosis, is heatstroke.

Preventing Anhidrosis

Doctors emphasize the need for patients to keep themselves in a cool environment. Using a water spray bottle to cool down can be beneficial. When the weather is warm, patients should wear loose and lightweight clothes and be careful not to exert themselves too much in their activities. Regularly and gently scrubbing the skin can also help, especially for those suffering from disorders that block their sweat glands.