Diagnosis
LGL syndrome is diagnosed in a person who has experienced episodes of abnormal heart racing (arrhythmias) who has a PR interval less than or equal to 0.12 second (120 ms) with normal QRS complex configuration and duration on their resting ECG. A short PR interval found incidentally on an ECG without episodes of tachycardia is simply a benign ECG variant.LGL can be distinguished from WPW syndrome because the delta waves seen in WPW syndrome are not seen in LGL syndrome. The QRS complex will also be narrow in LGL syndrome, as opposed to WPW, because ventricular conduction is via the His-Purkinje system. Lown–Ganong–Levine syndrome is a clinical diagnosis that came about before the advent of electrophysiology studies. It is important to be aware that not all WPW ECGs have a delta wave; the absence of a delta wave does not conclusively rule out WPW. Prognosis
Individuals with LGL syndrome do not carry an increased risk of sudden death. The only morbidity associated with the syndrome is the occurrence of paroxysmal episodes of tachycardia which may be of several types, including sinus tachycardia, atrioventricular nodal re-entrant tachycardia, atrial fibrillation, or atrial flutter. See also
Cardiac electrophysiology
Electrocardiogram
Electrophysiology study
Premature ventricular contraction
Wolff–Parkinson–White syndrome

References


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Cytoreductive therapy
In cases of advanced systemic mastocytosis or rare cases with indolent systemic mastocytosis with very troublesome symptoms, cytoreductive therapy can be indicated. ɑ-interferon. Given as subcutaneous injections. Side effects include fatigue and influenza-like symptoms
Cladribine (CdA). Chemotherapy which is given as subcutaneous injections. Side effects include immunodeficiency and infections. Tyrosine kinase inhibitors (TKI)
Midostaurin. TKI acting on many different tyrosine kinases, approved by FDA and EMA for advanced mastocytosis
Imatinib. Can have effect in rare cases without mutation in KIT(D816V)
Masitinib. Is being tested in trials. Not approved. Midostaurin - 60% respond. Avapritinib in trials; currently being tested but showing promise in reduction of tryptase levels.Allogeneic stem cell transplantation has been used in rare cases with aggressive systemic mastocytosis in patients deemed to be fit for the procedure. Other
Treatment with ultraviolet light can relieve skin symptoms, but may increase the risk of skin cancer. Prognosis
Patients with indolent systemic mastocytosis have a normal life expectancy. The prognosis for patients with advanced systemic mastocytosis differs depending on type of disease with MCL being the most serious form with short survival. Epidemiology
The true incidence and prevalence of mastocytosis is unknown, but mastocytosis generally has been considered to be an "orphan disease"; orphan diseases affect 200,000 or fewer people in the United States. Mastocytosis, however, often may be misdiagnosed, as it typically occurs secondary to another condition, and thus may occur more frequently than assumed.