Dermatomyositis associated with omalizumab therapy for severe asthma: a case report.

Dermatomyositis is not a known adverse effect of omalizumab therapy. DM has a low incidence, but potentially life threatening consequences. Amyopathic DM may represent up to 21% of cases of DM, with similar risks of malignancy and end organ dysfunction. DM has been associated with biologic therapy. Using the Naranjo adverse drug reaction (ADR) probability scale, our patient had a "probable" omalizumab related ADR. A more likely explanation is that the patient had underlying DM that remained occult due to chronic corticosteroid therapy. Our case highlights the need for clinical vigilance and maintenance of a broad differential when patients on biologic therapies present with cutaneous eruptions. In our patient, the cutaneous clinical features of DM became pronounced over serial assessments. Laboratory markers may be deceptively normal, as in amyotrophic DM, or confounded by ongoing corticosteroid therapy. There are important clinical implications of prompt diagnosis, given the association of DM with end organ disease including interstitial lung disease, and possible concomitant malignancy.