Impaired Presynaptic High-Affinity Choline Transporter Causes a Congenital Myasthenic Syndrome with Episodic Apnea.

The neuromuscular junction (NMJ) is one of the best-studied cholinergic synapses. Inherited defects of peripheral neurotransmission result in congenital myasthenic syndromes (CMSs), a clinically and genetically heterogeneous group of rare diseases with fluctuating fatigable muscle weakness as the clinical hallmark. Whole-exome sequencing and Sanger sequencing in six unrelated families identified compound heterozygous and homozygous mutations in SLC5A7 encoding the presynaptic sodium-dependent high-affinity choline transporter 1 (CHT), which is known to be mutated in one dominant form of distal motor neuronopathy (DHMN7A). We identified 11 recessive mutations in SLC5A7 that were associated with a spectrum of severe muscle weakness ranging from a lethal antenatal form of arthrogryposis and severe hypotonia to a neonatal form of CMS with episodic apnea and a favorable prognosis when well managed at the clinical level. As expected given the critical role of CHT for multisystemic cholinergic neurotransmission, autonomic dysfunctions were reported in the antenatal form and cognitive impairment was noticed in half of the persons with the neonatal form. The missense mutations induced a near complete loss of function of CHT activity in cell models. At the human NMJ, a delay in synaptic maturation and an altered maintenance were observed in the antenatal and neonatal forms, respectively. Increased synaptic expression of butyrylcholinesterase was also observed, exposing the dysfunction of cholinergic metabolism when CHT is deficient in vivo. This work broadens the clinical spectrum of human diseases resulting from reduced CHT activity and highlights the complexity of cholinergic metabolism at the synapse.

Kawasaki shock syndrome complicating a recurrence of Kawasaki disease.

We describe a case of recurrent Kawasaki disease (KD) in a non-Asian 6-year-old boy who had been diagnosed with typical KD without cardiac involvement at age 3 years. He was admitted to the PICU 3 years later for heart failure, hypotension, and deterioration of his general condition. Ultrasonography revealed left ventricular dysfunction with a 44% ejection fraction and grade I mitral valve failure without coronary artery involvement. Subsequent observation of hyperemic conjunctiva, bilateral cervical adenopathies with erythematous skin (normal neck ultrasound and computed axial tomography findings), peeling of the fingertips at day 8 of the illness, and occurrence of an inflammatory syndrome led to a diagnosis of incomplete recurrent KD with a clinical picture of Kawasaki shock syndrome (KSS). Clinical improvement was rapidly obtained after intravenous immunoglobulin and intravenous corticosteroid therapy (30 mg/kg per day for 3 subsequent days). Left ventricular function gradually improved, with ultrasound returning to normal after 3 months. Diagnosis was difficult to establish because of the recurrence of the disease and the incomplete clinical picture, with clinical features of KSS. Physicians need to be aware of these pitfalls in the management of patients with clinical signs of KD.