On being metachromatic: mystique and misunderstanding in mastocytosis.
We report on the outcome of 4 patients with therapy-resistant systemic mast cell activation disease (MCAD) treated with the anti-IgE monoclonal antibody omalizumab in compassionate use. Two patients achieved an impressive persistent clinical response to treatment with omalizumab. In the third patient symptoms gradually improved. In the fourth patient omalizumab treatment had to be discontinued due to intolerable mast cell mediator-induced symptoms. In conclusion, omalizumab can lessen the intensity of the symptoms of systemic MCAD. Hence, omalizumab should be considered as a therapeutic option in cases of systemic MCAD that are resistant to evidence-based therapy.