Which are the causes of Urticaria pigmentosa?

Urticaria pigmentosa, also known as cutaneous mastocytosis, is a rare skin condition characterized by the presence of brownish-red or yellowish-brown patches on the skin. These patches are caused by an excessive accumulation of mast cells, a type of immune cell, in the skin. While the exact cause of urticaria pigmentosa is not fully understood, several factors have been identified as potential contributors to the development of this condition.

Genetic Factors

Genetic factors are believed to play a significant role in the development of urticaria pigmentosa. Studies have shown that mutations in certain genes, such as KIT and KITLG, can lead to an abnormal proliferation and accumulation of mast cells in the skin. These genetic mutations are thought to be inherited in an autosomal dominant manner, meaning that a person only needs to inherit the mutated gene from one parent to develop the condition.

Environmental Triggers

While genetic factors are important, environmental triggers can also contribute to the development of urticaria pigmentosa. Exposure to certain substances or conditions can cause mast cells to release chemicals, such as histamine, which leads to the characteristic skin symptoms. Common triggers include:

• Temperature changes: Hot baths, showers, or exposure to extreme temperatures can trigger mast cell activation and the appearance of skin lesions.


• Friction: Rubbing or scratching the affected skin can cause mast cells to release chemicals and worsen the symptoms.


• Pressure: Applying pressure to the skin, such as from tight clothing or leaning on a surface, can trigger mast cell degranulation.


• Emotional stress: Stress and anxiety can stimulate mast cell activity and exacerbate the symptoms of urticaria pigmentosa.


• Certain medications: Some medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids, have been reported to trigger mast cell activation in individuals with urticaria pigmentosa.

Hormonal Factors

Hormonal factors may also contribute to the development or worsening of urticaria pigmentosa. It has been observed that symptoms tend to improve during childhood and adolescence, while they may worsen during pregnancy or in women taking hormone replacement therapy. Fluctuations in hormone levels, particularly estrogen, are thought to influence mast cell activity and the severity of symptoms.

Other Factors

In addition to the aforementioned factors, there are other potential contributors to the development of urticaria pigmentosa:

• Infections: Certain infections, such as viral or bacterial infections, have been associated with the onset or exacerbation of urticaria pigmentosa.


• Allergies: Some individuals with urticaria pigmentosa may have underlying allergies that can trigger mast cell activation and worsen the symptoms.


• Exposure to chemicals: Contact with certain chemicals, such as dyes, fragrances, or preservatives, can lead to mast cell degranulation and the appearance of skin lesions.

It is important to note that while these factors are believed to contribute to the development of urticaria pigmentosa, the condition can vary greatly among individuals. Some individuals may experience mild symptoms that are easily managed, while others may have more severe and persistent symptoms. If you suspect you have urticaria pigmentosa or are experiencing unexplained skin lesions, it is crucial to consult with a healthcare professional for an accurate diagnosis and appropriate management.