Hyperhidrosis is a medical condition defined by sweating that is significantly beyond what is required for normal body temperature regulation. This excessive perspiration is often unpredictable and can occur even when a person is cool, resting, or not under emotional stress. Research confirms that there is a strong hereditary component to this disorder, leading many to investigate the precise genetic mechanism.
Distinguishing Types of Hyperhidrosis
The term hyperhidrosis encompasses two main categories distinguished by their cause. Secondary Hyperhidrosis results from an underlying medical issue or a side effect of certain medications. This form of excessive sweating is considered a symptom of another condition, such as diabetes, thyroid problems, or menopause, and is not inherited genetically.
The second category is Primary Focal Hyperhidrosis (PFH), which accounts for the vast majority of cases. This form is not caused by another medical condition or drug but results from an over-activation of the sympathetic nervous system. It typically affects specific areas, most commonly the underarms, hands, feet, or face, and often begins in childhood or adolescence. This primary, localized form of the condition has a clear genetic link.
The Inheritance Pattern of Primary Hyperhidrosis
Genetic studies have concluded that Primary Focal Hyperhidrosis is inherited in an autosomal dominant manner. This means a person only needs to inherit one copy of the altered gene from either parent to have an increased susceptibility to developing the condition. The term “autosomal” indicates that the gene is located on a non-sex chromosome, meaning the trait affects both males and females equally.
PFH does not typically follow a recessive pattern, which would require a person to inherit two copies of the altered gene. Evidence supporting the dominant pattern includes the high percentage of patients who report a family history. Some studies find that up to 62% of those affected have a family member with the condition.
Although the exact genes have not been fully isolated, genetic linkage studies have identified specific regions on chromosomes that are associated with the condition. For example, one of the most studied areas is on chromosome 14 (14q11.2–q13), which has been linked to palmar hyperhidrosis. Other research suggests links to chromosomes 2 and 16, pointing to the possibility that the condition is polygenic, meaning it is influenced by multiple genes. The prevailing model remains autosomal dominant transmission.
What Autosomal Dominant Means for Families
The designation of autosomal dominant inheritance has direct implications for families dealing with Primary Focal Hyperhidrosis. If one parent has the condition, there is a 50% chance that any child will inherit the gene variant associated with the disorder. This probability applies to each pregnancy independently.
An important aspect of this inheritance is a phenomenon known as reduced or incomplete penetrance. This means that while an individual may inherit the dominant gene, they might never develop the physical symptoms of excessive sweating. The gene is present in their DNA, but it does not fully express itself. This explains why the condition can seemingly “skip” a generation, only to reappear later.
This variability highlights that genetics alone do not determine the condition, as environmental factors and other genetic elements also play a role. Medical professionals often place importance on gathering a detailed family medical history when diagnosing a patient. Understanding the dominant nature of the condition helps families anticipate the likelihood of recurrence and manage expectations for future generations.