Systemic mastocytosis is a blood disorder that can affect many different body systems. Individuals with the condition can develop signs and symptoms at any age, but it usually appears after adolescence.
Signs and symptoms of systemic mastocytosis often include extreme tiredness (fatigue), skin redness and warmth (flushing), nausea, abdominal pain, bloating, diarrhea, the backflow of stomach acids into the esophagus (), nasal congestion, shortness of breath, low blood pressure (hypotension), lightheadedness, and headache. Some affected individuals have attention or memory problems, anxiety, or depression. Many individuals with systemic mastocytosis develop a skin condition called urticaria pigmentosa, which is characterized by raised patches of brownish skin that sting or itch with contact or changes in temperature. Nearly half of individuals with systemic mastocytosis will experience severe allergic reactions (anaphylaxis).
There are five subtypes of systemic mastocytosis, which are differentiated by their severity and the signs and symptoms. The mildest forms of systemic mastocytosis are the indolent and smoldering types. Individuals with these types tend to have only the general signs and symptoms of systemic mastocytosis described above. Individuals with smoldering mastocytosis may have more organs affected and more severe features than those with indolent mastocytosis. The indolent type is the most common type of systemic mastocytosis.
The severe types include aggressive systemic mastocytosis, systemic mastocytosis with an associated hematologic neoplasm, and mast cell leukemia. These types are associated with a reduced life span, which varies among the types and affected individuals. In addition to the general signs and symptoms of systemic mastocytosis, these types typically involve impaired function of an organ, such as the , . The organ dysfunction can result in an abnormal buildup of fluid in the abdominal cavity (ascites). Aggressive systemic mastocytosis is associated with a loss of bone tissue (osteoporosis and osteopenia) and multiple bone fractures. Systemic mastocytosis with an associated hematologic neoplasm and mast cell leukemia both involve blood cell disorders or blood cell cancer (). Mast cell leukemia is the rarest and most severe type of systemic mastocytosis.
Individuals with the milder forms of the condition generally have a normal or near normal life expectancy, while those with the more severe forms typically survive months or a few years after diagnosis.