VP.90 Is an early diagnosis of congenital and childhood forms of myotonic dystrophy type 1 possible? Clinical and electromyographic description of case series

Abstract

Myotonic dystrophy Type 1 (DM1) is the most common among muscular dystrophies in patients of any age and among all hereditary neuromuscular diseases in adults. Myotonia is the leading symptom in DM1 and may appear at any stage of the disease. Clinical myotonia (CM) and reports on electrical myotonia (EM) are delayed after the onset in patients with congenital (CDM1) and childhood-onset (ChDM1) forms of DM1 making it difficult to diagnose and prevent fatal complications in patients with early onset.The description of 9 patients with CDM1 and 4 patients with ChDM1 aged from 2 months to 34 years is demonstrated. 11 patients (14.8±10.0 years) underwent electromyography in 16 muscles with the analysis of spontaneous activity and motor unit action potentials pattern on needle electromyography (needle EMG) in skeletal muscle. The diagnosis was confirmed on the basis of clinical, paraclinical manifestations of the disease and increase CTG-repeats >50 in <i>DMPK</i>. The onset with respiratory failure (66.7% - CDM1) and/or dysphagia, diffuse hypotonia, high-arched palate, club feet (100% - CDM1), facial diplegia (100% - CDM1 and ChDM1), speech delay (100% - ChDM1), mental retardation and/or psychiatric disorders (100% - ChDM1) were noted as the first symptoms of CDM1 and ChDM1. All patients with CDM1 were observed for a long time as cerebral palsy patients. CM was absent in 5 patients aged from 2 months to 9 years; in 8 patients the onset of CM was revealed at the age of 11.0±4.1 years. EM was revealed in all patients with CM, while the rest of the patients showed an increased insertional activity on needle EMG and single myotonic discharges in distal muscles. A myopathic pattern in needle EMG was detected in 9 out of 10 patients. All mothers had the classic form of DM1 with the onset of the disease in 4 (30.8%) of them within 10.3±3.3 years after DM1 onset in their children. In the absence of CM, the clinical picture and clinical improvement after birth causes DM1 patients to be misdiagnosed with cerebral palsy. Therefore, testing for CDM1 should be carried out if dysphagia, facial diplegia, high-arched palate and club feet are present. ChDM1 should be carried out at the onset of the disease with facial diplegia, speech delay, mental retardation and/or psychiatric disorders. The combination of the described symptoms with a myopathic pattern in needle EMG and/or a family history of DM1 makes it possible to diagnose CDM1 and ChDM1 at the onset of the disease.