Erythromelalgia or Mitchells disease (after Silas Weir Mitchell) is a rare vascular peripheral pain disorder in which blood vessels, usually in the lower extremities or hands, are episodically blocked (frequently on and off daily), then become hyperemic and inflamed. There is severe burning pain (in the small fiber sensory nerves) and skin redness. The attacks are periodic and are commonly triggered by heat, pressure, mild activity, exertion, insomnia or stress. Erythromelalgia may occur either as a primary or secondary disorder (i.e. a disorder in and of itself or a symptom of another condition). Secondary erythromelalgia can result from small fiber peripheral neuropathy of any cause, polycythemia vera, essential thrombocytosis, hypercholesterolemia, mushroom or mercury poisoning, and some autoimmune disorders. Primary erythromelalgia is caused by mutation of the voltage-gated sodium channel α-subunit gene SCN9A. In 2004 erythromelalgia became the first human disorder in which it has been possible to associate an ion channel mutation with chronic neuropathic pain, when its link to the SCN9A gene was initially published in the Journal of Medical Genetics. Later that year, in an article in The Journal of Neuroscience, Cummins et al., demonstrated, using voltage clamp recordings, that these mutations enhanced the function of NaV1.7 sodium channels, which are preferentially expressed within peripheral neurons.
Other side effects include redness, swelling, peeling or tenderness on the hands or feet (hand foot syndrome), constipation, stomach pain, nausea and muscle pain.Erdafitinib may cause serious eye problems, including inflamed eyes, inflamed cornea (front part of the eye) and disorders of the retina, an internal part of the eye. Patients are advised to have eye examinations intermittently and to tell their health care professional right away if they develop blurred vision, loss of vision or other visual changes. History
The efficacy of erdafitinib was studied in a clinical trial (NCT02365597) that included 87 adults with locally advanced or metastatic bladder cancer, with FGFR3 or FGFR2 genetic alterations, that had progressed following treatment with chemotherapy. The overall response rate in these adults was 32.2%, with 2.3% having a complete response and almost 30% having a partial response. The response lasted for an average of approximately five-and-a-half months. The trial was conducted in Asia, Europe, and the United States.Erdafitinib received an accelerated approval. Further clinical trials are required to confirm erdafitinibs clinical benefit and the sponsor is conducting or plans to conduct these studies. Erdafitinib was also granted breakthrough therapy designation.The FDA granted the approval of Balversa to Janssen Pharmaceutical. The FDA also approved the therascreen FGFR RGQ RT-PCR Kit, developed by Qiagen Manchester, Ltd., for use as a companion diagnostic with erdafinitib for this therapeutic indication. References
External links
"Erdafitinib". Drug Information Portal. U.S. National Library of Medicine.