Systemic mastocytosis

Overview

Systemic mastocytosis is a rare disorder characterized by the overproduction of mast cells, a type of white blood cell crucial for immune response. Normally, mast cells protect against disease by responding to allergens and other threats. In systemic mastocytosis, however, these cells abnormally multiply, leading to accumulation in various body parts such as skin, bone marrow, and digestive tract. This often results in symptoms similar to allergic reactions and severe inflammation that can cause organ damage. Common triggers include alcohol, spicy foods, insect stings, and certain medications.

While there is no cure for systemic mastocytosis, symptoms and complications are manageable. Most people experience mild symptoms manageable with medication and avoidance of triggers. However, symptoms may worsen or progress to cancer in some cases. All individuals with this condition face an increased risk of anaphylaxis, a severe, life-threatening allergic reaction.

There are six types of systemic mastocytosis, each varying in presentation and severity:

• Indolent systemic mastocytosis: The most common form, characterized by a gradual increase in abnormal mast cells affecting the skin, liver, spleen, and gastrointestinal tract. Symptoms develop slowly over several years, and most individuals manage these with medication, maintaining normal lifespans.
• Mast cell leukemia: A rare progression of systemic mastocytosis to acute myeloid leukemia.
• Systemic smoldering mastocytosis: In this type, abnormal mast cells proliferate primarily in the liver and spleen, potentially leading to organ enlargement.
• Mast cell sarcoma: Very rare, this involves tumors composed of abnormal mast cells that aggressively invade tissues.
• Systemic mastocytosis with associated hematologic neoplasm: This form coexists with blood disorders like myeloproliferative neoplasms and myelodysplastic syndrome, affecting approximately one-fifth of those diagnosed.
• Aggressive systemic mastocytosis: Abnormal mast cells in the bone marrow disrupt blood cell production, causing conditions such as leukopenia and anemia, and may infiltrate bones, increasing fracture risk.

Each type of systemic mastocytosis poses different challenges and risks, generally correlating the severity of symptoms to the quantity of abnormal mast cells present.

Symptoms

Symptoms of systemic mastocytosis vary depending on the location where the excess mast cells accumulate. For instance, if they cluster in the stomach, it may result in the development of ulcers and abdominal discomfort. Occasionally, individuals with this condition may experience a sudden onset of multiple symptoms, only to have them dissipate afterward. Healthcare professionals may refer to this occurrence as a mastocytosis attack.

Common signs and symptoms include:

• Maculopapular skin lesions, or flat, red patches with several tiny bumps on it
• Bleeding disorders, bruising or anemia
• Hives, itching, or flushed face
• Diarrhea, vomiting, nausea, or abdominal pain
• Muscle and bone aches
• Swollen lymph nodes, the liver, or the spleen
• Depression, mood swings or difficulty focusing
• Extreme fatigue

Excess mast cells can accumulate in various parts of the body, including the skin, liver, spleen, bone marrow, and intestines. Sometimes, less common organs like the brain, heart, or lungs can also be affected by this buildup.

Experiencing symptoms like flushing, hives, or digestive issues does not automatically mean one have systemic mastocytosis, as these symptoms can be caused by other conditions too. However, if the symptoms are consistently experienced together or if they persist, it is essential to consult a healthcare provider for proper diagnosis and treatment.

Causes

Most cases of systemic mastocytosis, a condition where excessive mast cells accumulate in tissues and organs causing inflammation, are linked to a mutation in the KIT gene. This mutation, which is found in about 80% of affected individuals, is not inherited but occurs after conception. The KIT gene is crucial for the development of various cell types, including blood cells and mast cells. The mutation leads to the overproduction of mast cells, which release inflammatory substances like histamine, leukotrienes, and cytokines, contributing to the symptoms of the disease.