Anti-synthetase syndrome in a child with pneumomediastinum: a case report and literature review.

BACKGROUND: Anti-synthetase syndrome (ASS) is a group of rare clinical subtypes within inflammatory myopathies, predominantly affecting adult females. Instances of critical illness associated with ASS in children are even rarer.

CASE PRESENTATION: We report the case of a 7-year-old boy finally diagnosed with ASS, combined with pneumomediastinum. He presented with intermittent fever persisting for 12 days, paroxysmal cough for 11 days, chest pain, and shortness of breath for 4 days, prompting admission to our hospital. Pre-admission chest CT revealed diffuse pneumomediastinum, subcutaneous pneumatosis in the neck and bilateral chest wall, consolidation, atelectasis, and reticular nodular shadowing in both lungs, as well as pericardial effusion and bilateral pleural effusions. Laboratory tests revealed a positive result for serum MP immunoglobulin M (MP-IgM) and MP immunoglobulin G (MP-IgG). The patient was initially diagnosed with mycoplasma pneumoniae (MP) infection, and following 3 days of antibiotic treatment, the patient's tachypnea worsened. Positive results in muscle enzyme antibody tests included anti-PL-12 antibody IgG, anti-Jo-1 antibody IgG, and anti-RO-52 antibody IgG. Ultrasonography detected moderate effusions in the right shoulder, bilateral elbow, and knee joints. Corticosteroids pulse therapy was initiated on the 27th day following disease onset, and continued for 3 days, followed by sequential therapy for an additional 12 days. The child was discharged on the 43rd day, and subsequent follow-up revealed a significant improvement in consolidation and interstitial lesions in both lungs.

CONCLUSIONS: ASS in children may combine with rapidly progressive interstitial lung disease (RPILD) and pneumomediastinum. It is crucial to promptly identify concurrent immunologic abnormalities during the outbreak of MP, particularly when the disease exhibits rapid progression with ineffective conventional antibiotic therapy.