Mastocytosis

Mastocytosis is a disorder of excessive mast cell proliferation, which is now classified as a myeloproliferative neoplasm ⁶.  Two clinical entities fall under the mastocytosis umbrella : cutaneous (urticaria pigmentosa) and systemic mastocytosis (with or without cutaneous manifestations). The article deals primarily with the latter.

Pathology

Mast cells are bone marrow derived cells that are widely distributed in tissues. They store various biologically active mediators, such as heparin and histamine. Mediator release from mast cells has a central role in the development of type 1 hypersensitivity ¹. 

In systemic mastocytosis, abnormal proliferation and microscopic infiltration of mast cells involves skin, bone marrow, gastrointestinal tract, liver and spleen. It is thought that the effects of mastocytosis relate at least in part to mediator release ⁷.

Clinical presentation

There is considerable heterogeneity in the presentation of mastocytosis, and in the rate of disease progression. Clinical features include:

• cutaneous manifestations
• flushing
• hypotension and syncope
• abdominal pain
• nausea, vomiting and diarrhoea
• malabsorption
• bone pain and pathological fractures
• associated haematological disorders ⁷

Radiographic features

Are best addressed according to system rather than modality. Most features are not specific to the disease but may suggest the diagnosis in the correct clinical setting.

Skeletal ^4-5

Bone involvement in mastocytosis can be either lytic, sclerotic or mixed process. Diffuse involvement tends to be more common^11. Usually, the radiographic appearance is that of sclerosis involving primarily axial skeleton and the ends of long bones. In some patients there is generalised osteoporosis with risk of pathological fractures.

Abdominal

• peptic ulceration
• diffuse small bowel thickening
• omental and mesenteric thickening ⁹
• hepatosplenomegaly
• ascites
• lymphadenopathy

Pulmonary (rare) ^2,8

• pulmonary nodules

See also

• differential diagnosis for diffuse bony sclerosis