[en] Action Potentials ; Adult ; Autoimmune Diseases/diagnosis ; Chromosomes, Human, Pair 2/genetics/ultrastructure ; Chromosomes, Human, Pair 9/genetics/ultrastructure ; Diagnosis, Differential ; Electromyography ; Genetic Heterogeneity ; Humans ; In Situ Hybridization, Fluorescence ; Ion Transport ; Male ; Muscarinic Antagonists/therapeutic use ; Myasthenia Gravis/diagnosis ; Myasthenic Syndromes, Congenital/diagnosis/drug therapy/genetics ; Neostigmine/diagnostic use ; Neural Conduction ; Protein Subunits ; Quinidine/therapeutic use ; Receptors, Muscarinic/genetics/physiology ; Translocation, Genetic
[en] A 27-year-old man complained of cervicoscapular and forearm weakness and amyotrophy. Electromyographic evaluation showed neuromuscular transmission dysfunction and a repetitive compound muscle action potential to a single stimulus. Prostigmine did not improve neuromuscular transmission. The genetic analysis of the patient's lymphocytes demonstrated a chromosomic 2q31-9p27 translocation. The combination of the clinical and electrophysiological data as well as the lack of auto-immunity signs against neuromuscular junction constituents led to the diagnosis to congenital postsynaptic myasthenic syndrome also called slow channel syndrome. This congenital myasthenic syndrome is for the first time associated with an autosomal translocation 2q31-9p27.