Inclusion Criteria

Inclusion criteria:

- Histological proven mastocytosis (cutaneous or systemic);

- Diagnosis made by one marrow unction and/or skin biopsy or other histological work
up;

- Age: 18-70 years

Exclusion criteria

- Age <18 years;

- Known hypersensitivity to omalizumab or any of its components;

- History of cancer in previous 5 years;

- Patients with serious infections;

- Patients with active tuberculosis or undergoing anti-TB therapy;

- Patients currently treated with systemic immunosuppressive agents;

- Female patients who are pregnant or breast feeding;Contraception must be performed by
a save reliable and accept method such as oral or implanted contraceptives,
intravaginal or male preservatives or permanent methods such as tubal ligation.

- Patients with known positivity for human immunodeficiency virus (HIV). HIV screening
will be performed by an HIV 1/2 Antibody-detection test.

Note: Specific immunotherapy for insect sting allergy is no exclusion criteria.