What Is Cutaneous Mastocytosis?

Overview

Cutaneous mastocytosis is a rare disorder caused by overproduction and accumulation of mast cells (white blood cells) in the skin, causing itchy sores, typically dark red or brown. It occurs when the normal mast cells mutate, leading to their overproduction and aggregation, which results in a continuous allergic response in the organism. Three main types of cutaneous mastocytosis are distinguished; however, all of them affect only the patient's skin, manifesting itself as skin lesions of different forms and extent around the body. Cutaneous mastocytosis affects only the individual's skin; if the disease is more extensive and the build-up of mast cells is observed in other tissues and internal organs, it is called systemic mastocytosis.¹

How does mastocytosis develop, and what are mast cells?

Mastocytosis is a rare disorder (it is estimated to affect one out of 10,000 – 20,000 people) that involves abnormal production and accumulation of incorrectly functioning mast cells. Mast cells, also known as white blood cells, are spread throughout the body and play a pivotal role in the immune system. They trigger immune and allergic reactions by releasing histamine, which in turn makes the blood vessels expand and, thus the skin swollen and itchy.

Generally, when the organism is defended, the normal mast cells stop multiplying and releasing histamine, and the organism's state goes back to normal. In the case of mastocytosis, mast cells do not stop growing even when the organism is not threatened anymore. They keep multiplying and accumulate in different parts of the body. The overproduction of the abnormal mast cells leads to increased histamine levels, causing a continuous immune response.^1,2

The two main categories of mastocytosis

There are two main categories of mastocytosis, based on the location of abnormal mast cell build-up, namely:

Systemic mastocytosis

The abnormal mast cells accumulate in many internal organs, such as the spleen, lungs, and liver, but also in the gastrointestinal tract, lymph nodes, and bone marrow. The aggregation of mast cells in various parts of the body impairs the functions of specific organs. For instance, the aggregates in bone marrow can disrupt the production of blood cells, while the build-up of mast cells in the stomach might lead to overproduction of stomach acid, potentially causing ulcers. This type of disorder generally affects adults.

Cutaneous mastocytosis

For cases of cutaneous mastocytosis, the mast cell clusters are formed solely in the skin. This type of mastocytosis typically affects children but, in rare cases, might be diagnosed in young adults.

Based on the clinical appearance and the course of the disorder, three different categories of cutaneous mastocytosis can be further distinguished, namely mastocytoma and maculopapular cutaneous mastocytosis, which are more common, and diffuse cutaneous mastocytosis, which typically is diagnosed less frequently. Mastocytoma manifests as a single skin lesion or up to three of them. It is a mild type of disorder, being diagnosed in early childhood, which typically subsides with age. On the other hand, maculopapular cutaneous mastocytosis is more extensive and causes symptoms in the entire body; usually, the scalp, neck, trunk, and extremities are covered with skin lesions. Diffuse cutaneous mastocytosis is the most severe type of the disease and usually affects children. The individual lesions typical for cutaneous mastocytosis are not observed in the cases of patients with diffuse cutaneous mastocytosis. Instead, the individual's skin is diffusely thickened and exhibits a coarse texture.³

Signs, symptoms, and diagnostic criteria for cutaneous mastocytosis

Generally, the symptoms of cutaneous mastocytosis resemble a skin allergic reaction. Individuals most often experience the formation of lesions on the skin, such as bumps and spots. Moreover, the disorder might include other symptoms, such as flushing, headache, and fatigue, caused by the body’s immune response.

In the first stage of the diagnostic process, the development of cutaneous mastocytosis is determined based on the physical examination, specifically on two major criteria, namely the presence of skin lesions and a positive Darier’s sign.

Darier’s sign is the red halo that forms around the lesion, elicited upon rubbing or scratching. It is very characteristic for patients with cutaneous mastocytosis, making it a crucial diagnostic tool for cutaneous mastocytosis.

Additionally, in the next stage, the diagnosis is confirmed by performing a skin biopsy, which involves taking a small skin sample and examining the amount of mast cells present. Moreover, systemic mastocytosis must be excluded to be diagnosed with cutaneous mastocytosis. Therefore, the patients should only exhibit clusters of mast cells in the skin, with no signs of aggregation of mast cells in internal organs. This is examined through blood tests, bone marrow biopsy (detection of an abnormal amount of mast cells), or ultrasound scans (detection of liver enlargement, spleen, or other organs, which may be caused by mast cell build-up).

Suppose the patient develops skin lesions, which give a positive Darier’s sign. In that case, the skin biopsy confirms an abnormal amount of mast cells in the skin, and none of the performed tests confirm the mast cell build-up in the internal organs, the patient is usually diagnosed with cutaneous mastocytosis.⁴

What causes the development of cutaneous mastocytosis?

The development of cutaneous mastocytosis is associated with a genetic mutation, resulting in an overproduction of mast cells and aggregation in the patient's skin. It is not passed down through families; in very few cases, it might be diagnosed in more than one family member. In general, cutaneous mastocytosis is not classified as hereditary. The mutation occurs spontaneously without any specific reason being determined so far.¹

Treatment options

Unfortunately, no cure exists for cutaneous mastocytosis. Nevertheless, various treatment options exist to help manage the disorder's symptoms. The healthcare provider chooses the treatment option after the diagnosis and careful examination of the patient’s physical condition and the severity of the symptoms.

Steroid creams

In the mild and moderate cases of cutaneous mastocytosis, the symptoms can be treated with steroid creams (topical corticosteroids), which are applied directly on the skin and reduce inflammation and irritation of the tissues. They suppress the immune response by reducing the activity of various inflammatory cells, including mast cells.

Antihistamines

This type of medication can also be used to treat cutaneous mastocytosis. Antihistamines act by inhibiting the activity of histamine, the substance which causes inflammation. They are usually applied in the cases of allergic reactions.

UV light therapy

In some cases, ultraviolet (UV) light therapy might be applied, which, apart from the anti-inflammatory effects and reduced mast cell activity, improves the visual condition of the skin. This treatment aims to lighten dark skin lesions by reducing hyperpigmentation and improving the overall skin texture and tone. However, this type of treatment has to be performed under the close supervision of the healthcare provider due to the potential risks and side effects associated with UV light exposure.^5,6

Living with cutaneous mastocytosis

People suffering from cutaneous mastocytosis usually manage the disorder by avoiding the environments and activities which can cause more severe allergic reactions and deterioration of the skin condition. The symptoms of cutaneous mastocytosis can be alleviated by avoiding certain substances, medicines, or physical factors which can cause further inflammation and irritation of the skin. Additionally, lifestyle modifications such as implementing a healthy diet and engaging in physical activities might improve the patient’s health condition. All the adjustments combined with medical supervision and treatment help minimise the severity of the symptoms and improve the quality of life for those affected by cutaneous mastocytosis.¹

Summary

Cutaneous mastocytosis is an uncommon health condition characterised by an excessive production of mast cells, which subsequently form clusters in the patient's skin. The disorder is diagnosed by a physical examination of the skin condition performed by the healthcare provider. It is usually based on two major characteristics of cutaneous mastocytosis, namely the detection of skin lesions and a positive Darier’s sign. No cure exists for cutaneous mastocytosis and the available treatment options aim at symptom alleviation. Mild and moderate cases of cutaneous mastocytosis can be treated with steroid creams, which reduce the inflammation of the skin, whereas in more severe cases antihistamines are administered. Cutaneous mastocytosis affects only the skin of the patient. If it is more extensive and the mast cell build-ups are detected in the internal organs, the condition is referred to as systemic mastocytosis.