Atteintes pulmonaires des polymyosites et dermatopolymyosites

[Lung is also involved in juvenile dermatomyositis]

Juvenile dermatomyositis is the leading cause of chronic idiopathic inflammatory myopathy of auto-immune origin in children. Lung involvement in inflammatory myopathies is well described in adults, involving mostly interstitial lung disease, aspiration pneumonia and alveolar hypoventilation. We propose to describe its specificities in children. Pulmonary involvement may be asymptomatic and therefore must be systematically screened for. In case of clinical or functional respiratory abnormality, a chest computed tomographic (CT) scan is necessary. In children, a decrease of respiratory muscle strength seems common and should be systematically and specifically searched for by non-invasive and reproducible tests (sniff test). Interstitial lung disease usually associates restrictive functional defect, impairment of carbon monoxide diffusion and interstitial lung disease on CT scan. As in adults, the first-line treatment of juvenile dermatomyositis is based on corticosteroids. Corticosteroid resistant forms require corticosteroid bolus or adjuvant immunosuppressive drugs (methotrexate or cyclosporine). There is no consensus in pediatrics for the treatment of diffuse interstitial lung disease. Complications of treatment, including prolonged steroid therapy, are frequent and therefore a careful assessment of the treatments risk-benefit ratio is necessary, especially in growing children.

[Acute interstitial lung disease revealing antisynthetase syndrome]

INTRODUCTION

The antisynthetase syndrome is characterized by the presence of myositis, interstitial lung disease, arthritis, Raynaud's phenomenon, mechanics hands and anti-Jo1 antibody (histidyl tRNA synthetase). The prognosis of this syndrome is closely related to the severity of lung disease. Myositis can occur several years after lung disease and some patients with interstitial lung disease associated with anti-Jo1 antibodies will not suffer from muscle disease.

CASE-REPORT

We report the case of a 69-year-old man admitted to the medical intensive care unit for acute respiratory insufficiency related to rapidly progressive interstitial lung disease. Antisynthetase syndrome was diagnosed the presence of wrists' arthritis, 'mechanic's hands and anti-Jo1 antibodies. Despite the dramatic efficacy of corticosteroid therapy on ventilation parameters, the patient died from a Pseudomonas Aeruginosa nosocomial ventilator-acquired pneumonia.

CONCLUSION

Our case emphasizes the importance to search for anti-Jo1 antibodies in the presence of interstitial lung disease. During the course of antisynthetase syndrome, the occurrence of interstitial lung disease is almost always constant and is correlated with poor prognosis.

[Acute interstitial pneumonia: diagnostic approach and management]

Acute interstitial pneumonia (AIP) encompasses a spectrum of pulmonary disorders characterized by involvement of the lung interstitium and distal airways (bronchioles and alveoli). The onset of respiratory symptoms is acute, most often within two weeks. Most AIP take place de novo, but sometimes represent an acute exacerbation of chronic lung disease. The clinical presentation of AIP comprises rapidly progressive dyspnoea, associated sometimes with cough, fever, myalgia and asthenia. Chest radiography shows diffuse pulmonary opacities. The associated hypoxemia may be severe enough to cause acute respiratory failure. Underlying aetiologies are numerous and variable, particularly in relation to the underlying immune status of the host. Various histopathological entities may be responsible for AIP although diffuse alveolar damage is the predominant pattern. The diagnostic approach to a patient presenting with AIP is to try to determine the most likely underlying histopathological pattern and to search for a precise aetiology. It relies mainly on a meticulous clinical evaluation and accurate biological investigation, essentially guided by the results of bronchoalveolar lavage performed in an area identified by abnormalities on high resolution computed tomography of the lungs. Initial therapeutic management includes symptomatic measures, broad-spectrum antibiotic treatment adapted to the clinical context, frequently combined with systemic corticosteroid therapy.