Case
A 12-month-old Japanese boy with interstitial lung disease was
transferred to our hospital due to progressive respiratory failure
despite receiving systemic corticosteroids, including methylprednisolone
pulse therapy. He was born at full term from nonconsanguineous parents.
His past medical history was only significant for mild motor
developmental delay. Family history revealed that his father was
undergoing further investigation of a chest X-ray abnormality. On
admission, vital signs were remarkable for tachypnea and hypoxia. The
respiratory rate was 50/min. SpO2 was variable between
90-95% with oxygen supplementation at 2 L/min via a nasal cannula. His
height and weight were 74.0 cm (50th percentile) and 8.1 kg (10th
percentile), respectively. He showed moderate intercostal retraction.
Respiratory distress worsened even after the second methylprednisolone
pulse therapy. A week after admission, his respiratory rate increased to
70/min, and his oxygen requirements were up to 3 L/min to maintain
SpO2 >90%. HCQ was administered orally to
improve his respiratory condition. In the eventual case of
unresponsiveness, we discussed lung transplantation with his parents and
consulted a transplant surgeon. Because SpO2 with the
conventional nasal cannula varied greatly depending on his activity,
such as sleeping or moving, we used HFNC (Optiflow™ junior, OPT316,
Fisher & Paykel Healthcare Co. Ltd., Auckland, New Zealand) with an
inspiratory oxygen fraction of 0.60 and flow rate of 15 L/min to
accurately monitor his oxygenation. The inspiratory oxygen fraction was
adjusted to maintain SpO2 ≥95%. Because the
SpO2 variation dramatically decreased with HFNC, we were
able to evaluate his oxygenation more accurately. After two weeks of HCQ
administration, his oxygen requirements gradually decreased. At that
time, SFTPC sequencing revealed a known pathogenic variation (c.
218T>C, p. Ile73Thr). His respiratory distress improved so
that we could change the HFNC to a conventional nasal cannula after five
weeks of HCQ treatment. Corticosteroid therapy was carefully tapered
because he temporarily experienced adrenal insufficiency. Four months
after admission, he was discharged with home oxygen therapy and
treatment with HCQ, hydrocortisone, and azithromycin. The biochemical
parameters of lung injury, such as lactate dehydrogenase (LDH) and Krebs
von den Lungen-6 (KL-6), fluctuated during the course of inpatient
treatment. The decrease in these parameters did not parallel with his
clinical improvement (Figure 1). Radiological findings also improved
several months after the clinical improvement.