Respiratory phenotypes of neuromuscular diseases: A challenging issue for pediatricians.

Neuromuscular disease (NMDs) encompass a heterogeneous group of genetic disorders, with respiratory problems of variable intensity and progression described at any pediatric age, from infancy to adolescence, and they are largely associated with significant lifelong morbidity and high mortality. Restriction of breathing, impaired gas exchange, decline of lung function and sleep disordered breathing progressively develop because of muscular weakness and culminate in respiratory failure. Depending on the disease progression, airways manifestations can take weeks to months or even years to evolve, thus depicting two major respiratory phenotypes, characterized by rapid or slow progression to respiratory failure. Assessing type and age at onset of airways problems and their evolution over time can support pediatricians in the diagnostic assessment of NMD. In addition, knowing the characteristics of patients' respiratory phenotype can increase the level of awareness among neonatologists, geneticists, neurologists, pulmonologists, nutritionists, and chest therapists, supporting them in the challenging task of the multidisciplinary medical care of patients. In this review we examine the issues related to the pediatric respiratory phenotypes of NMD and present a novel algorithm that can act as a guide for the diagnostic agenda and the key preventive or therapeutic interventions of airways manifestations. With prolonged survival of children with NMD, the advent of neuromuscular respiratory medicine, including accurate assessment of the respiratory phenotype, will help physicians to determine patients' prognoses and to design studies for the evaluation of new therapies.

A Challenging Diagnosis of Fluctuating Dyspnea: Myasthenia Gravis.

Isolated respiratory muscles weakness is an unusual presentation of Myasthenia Gravis (MG). We present a case of 49-year-old male with undiagnosed MG who presented with fluctuating dyspnea on exertion and at rest. There was no peripheral muscle involvement, diagnostic tests and standard electromyography was normal, and the serologic tests were negative. The repetitive nerve stimulation and Single Fiber Electromyography revealed the diagnosis of MG. Interestingly the patient did not have sufficient therapeutic response on first line agents and required immunoglobulins and corticosteroids due to respiratory muscle involvement. Since skeletal muscle weakness is a cardinal feature of MG, dyspnea may be fluctuating as in our patient causing further difficulty in diagnosis as the pulmonary function tests performed during remission may be normal. This presentation highlights the need to consider MG in the differential diagnosis of unexplained dyspnea on exertion/rest.