Case Report: Rapidly Progressive Interstitial Lung Disease in a 6-Year-Old

Table 1: Initial Labs on Presentation

Table 2: Labs Obtained After Patient Transferred to Our PICU

Upon arrival to our PICU, the patient’s tachypnea was slightly improved. The patient’s oxygen saturation was 92% while using the non-rebreather face mask. On examination, he was in respiratory distress with suprasternal and subcostal retractions, and auscultation revealed coarse breath sounds. The physical examination was notable for a swollen right wrist and right knee, concerning for septic arthritis. Gottron papules and a heliotrope rash were noted, along with digital ulcers (see Table 2). A chest X-ray showed bilateral airspace opacities concerning for acute respiratory distress syndrome (ARDS).

The PICU team initially thought the patient had developed ARDS secondary to septic arthritis. Thus, he was emergently taken to an operating room and intubated prior to an arthro­scopic knee washout to achieve source control. He was unable to be extubated following the procedure.

Synovial fluid cultures grew methicillin-susceptible Staphylococcus aureus. Treatment was initiated with vancomycin and piperacillin/tazobactam, initially, and then switched to nafcillin to narrow the spectrum of anti­microbial coverage.

The patient’s respiratory status continued to decline. He had difficulty maintaining oxygenation despite mechanical ventilation. A computed tomography (CT) chest scan was obtained, which showed diffuse bilateral airspace opacities (see Photo 4).

The patient’s respiratory status worsened despite appropriate antimicrobial therapy. We suspected the patient’s respiratory decline was due to underlying rapidly progressive ILD associated with CADM, rather than sepsis. We recommended immediately placing the patient on extracorporeal membrane oxygenation (ECMO) and initiating plasmapheresis. We later added high-dose steroids (30 mg/kg daily for three days, followed by 1 mg/kg every six hours). Serum anti-MDA5 antibody levels were ordered at the same time.

The patient’s respiratory status significantly improved following plasmapheresis. He was extubated three days after initiation of ECMO and was weaned off ECMO after five sessions of plasmapheresis.

The patient was found to have anti-MDA5 antibodies, and the patient was administered 575 mg/m² of intravenous rituximab (pediatric myositis dose for a patient with a BSA of <1.5), with a second dose one week later.