Mastocytosis can occur in a variety of forms:
Cutaneous mastocytosis (CM)
- The most common cutaneous mastocytosis is maculopapular cutaneous mastocytosis, previously named papular urticaria pigmentosa (UP), more common in children, although also seen in adults. Telangiectasia macularis eruptiva perstans (TMEP) is a much rarer form of cutaneous mastocytosis that affects adults. MPCM and TMEP can be a part of indolent systemic mastocytosis. This should be considered if patients develop any systemic symptoms
- Generalized eruption of cutaneous mastocytosis (adult type) is the most common pattern of mastocytosis presenting to the dermatologist, with the most common lesions being macules, papules, or nodules that are disseminated over most of the body but especially on the upper arms, legs, and trunk
- Diffuse cutaneous mastocytosis' has diffuse involvement in which the entire integument may be thickened and infiltrated with mast cells to produce a peculiar orange color, giving rise to the term "homme orange."
Cutaneous mastocytosis in children usually presents in the first year after birth and in most cases vanishes during adolescence.
Systemic mastocytosis (SM)
Systemic mastocytosis involves the bone marrow in the majority of cases and in some cases other internal organs, usually in addition to involving the skin. Mast cells collect in various tissues and can affect organs where mast cells do not normally inhabit such as the liver, spleen and lymph nodes, and organs which have normal populations but where numbers are increased. In the bowel, it may manifest as mastocytic enterocolitis.
There are five types of systemic mastocytosis:
- Indolent systemic mastocytosis (ISM). The most common SM (>90%)
- Smouldering systemic mastocytosis (SSM)
- Systemic mastocytosis with associated haematological neoplasm (SM-AHN)
- Aggressive systemic mastocytosis (ASM)
- Mast cell leukemia (MCL)