[The pitfalls of using diagnosis and treatment guidelines for patients with juvenile myasthenia gravis]

Even though evidence-based clinical guidelines are useful for the management of common diseases, there are several problems in applying such guidelines to patients with rare diseases. First, there are few references providing high-level evidence pertaining to such diseases, and randomized control as well as large cohort studies are lacking. Most grades of recommendation are “suggest” rather than “recommend” or, often, are based on “expert opinion”. Juvenile myasthenia gravis (MG) is a rare disease and has mainly been reported in East Asia. In 2014, evidence-based clinical guidelines for MG diagnosis and treatment were published in Japan. Since references were scarce, these guidelines were also based on expert opinions such as those of a few institutes or specialists who had gathered most of the patients in Japan. The guidelines might be of limited usefulness for general pediatricians or pediatric neurologists with no MG experience, and we should be aware of strengths and pitfalls when applying such guidelines. For example, while knowing when to start steroid administration or the appropriate steroid dose is feasible, the optimal timing of switching from an anti-cholinesterase drug to a steroid or adding an anti-inflammatory drug and how to decrease or stop steroid administration cannot be ascertained from the guidelines. The lack of references with high-level evidence makes the guidelines difficult to apply, since this would be the information most desired by clinicians. Another problem is that a recommendation may easily be reversed if opposing results are obtained in a single study of a rare disease. Thymectomy was recognized as not being beneficial for MG without thymoma but one recent study reversed this recommendation in the guidelines. Herein, we discuss pitfalls in applying diagnostic and treatment guidelines in patients with juvenile MG.