AAAAI Mast Cell Disorders Committee Work Group Report: Mast cell activation syndrome (MCAS) diagnosis and management.

Our current recommendations for diagnosing and treating primary mast cell (MC) activation syndrome make use of the latest studies and consensus guidelines for clinically recognizing systemic anaphylaxis in real time, regardless of whether allergen-triggered or other pathways are involved; our current understanding of the biomarkers secreted by activated MCs that best discriminate this disorder from other conditions; and the therapeutic drugs that might selectively affect those mediators or MCs themselves. Finding familial or somatic mutations of genes that cause MCs to be hyperactivatable would extend our diagnostic tools and potentially indicate new therapeutic interventions, targeting either the mutated gene product or the associated molecular pathway. In conclusion, we trust that the clinical, laboratory, and therapeutic criteria for primary MC activation syndromes described herein will provide clinicians with practical criteria of sufficient sensitivity and specificity to diagnose most cases without overdiagnosing the disorder in patients who likely have other conditions.

Mast Cell Activation Syndrome.

A 51-year-old woman with a history of asthma and Hashimoto's thyroiditis presented to the dermatology service with a chief complaint of "itchy bumpy rashes" that persisted beyond 24 hours. She noted that, 3 days prior to the onset of urticaria, a pyrroloquinoline quinone supplement had been started. The urticaria was accompanied by variable episodes of transient facial swelling and difficulty breathing. The patient noted that exposure to fish, nuts, and nonsteroidal anti-inflammatory drugs triggered facial swelling. Other reported findings included a 5-year history of diarrhea, sense of memory deterioration, concentration difficulties, and clinical manifestations of anomic aphasia. Although her allergy testing was "negative," she had been given the diagnoses of lactose intolerance and gastroesophageal reflux disease. Laboratory studies on initial presentation were significant for a positive history of antithyroperoxidase antibodies and elevated total complement activity. Medications included budesonide/formoterol, fluticasone/salmeterol, levothyroxine, albuterol, and fexofenadine 180 mg twice daily. Although her "rash" had initially responded to fexofenadine, it soon became refractory to treatment. Her family history was significant only for thyroid disease.