Clinical Outcomes of Low-Dose Methotrexate Therapy as a Second-Line Drug for Intravenous Immunoglobulin-Resistant Kawasaki Disease

PURPOSE: Intravenous immunoglobulin (IVIG) is the standard treatment for Kawasaki disease (KD). However, there is still no standard treatment for IVIG-resistant KD. This study aimed to evaluate the efficacy of low-dose methotrexate (MTX) as a treatment for IVIG-resistant KD. MATERIALS AND METHODS: We retrospectively analyzed 10-year data for patients with IVIG-resistant KD who were administered MTX at Severance Children's Hospital. RESULTS: The subjects included 75 patients with KD aged 5 months to 9.2 years who had been administered MTX. Their maximum body temperatures decreased significantly within 24 h of therapy. The patients' C-reactive protein levels were significantly lower 1 week after administering the first dose of MTX than those before treatment. No adverse effect for MTX was observed. CONCLUSION: MTX treatment of IVIG-resistant KD resulted in rapid defervescence, improvement of clinical symptoms, and normalization of acute-phase reactants in all patients. Thus, MTX could be a candidate treatment for IVIG-resistant KD.

Isolated pulmonary Langerhans cell histiocytosis in a 10-month-old infant

Langerhans cell histiocytosis (LCH) is characterized by clonal proliferation and accumulation of abnormal dendritic (Langerhans) cells in various organs. Pulmonary involvement, although rare in children, has been reported in 20%–50% of childhood cases of multisystem LCH. Isolated pulmonary LCH in children, especially in infants, is still rarer, but should be suspected in those with cystic lung disease. We report a case of a 10-month-old boy who presented with chronic dyspnea and whose chest computed tomography (CT) scan demonstrated cystic lesions. Lung biopsy established the diagnosis of LCH; microscopy revealed a background of lymphocytes and eosinophils with kidney-shaped abnormal cells. These abnormal cells were positive for S-100, CD207 (Langerin), and CD1a on immunohistochemical staining. Chemotherapy was administered using a cytotoxic agent (vinblastine) and a steroid. After 12 weeks of induction chemotherapy, although no significant change in cyst size was noted on chest CT, clinical symptoms improved. Consolidation chemotherapy was then administered for 1 year. Thereafter, chest CT findings demonstrated a significant decrease in cyst size and a significant increase in the volume of normal lung parenchyma. Therefore, aggressive treatment of isolated pulmonary LCH in infants with severe tissue destruction and symptoms seems warranted.

Suppression of the ERK–SRF axis facilitates somatic cell reprogramming

The molecular mechanism underlying the initiation of somatic cell reprogramming into induced pluripotent stem cells (iPSCs) has not been well described. Thus, we generated single-cell-derived clones by using a combination of drug-inducible vectors encoding transcription factors (Oct4, Sox2, Klf4 and Myc) and a single-cell expansion strategy. This system achieved a high reprogramming efficiency after metabolic and epigenetic remodeling. Functional analyses of the cloned cells revealed that extracellular signal-regulated kinase (ERK) signaling was downregulated at an early stage of reprogramming and that its inhibition was a driving force for iPSC formation. Among the reprogramming factors, Myc predominantly induced ERK suppression. ERK inhibition upregulated the conversion of somatic cells into iPSCs through concomitant suppression of serum response factor (SRF). Conversely, SRF activation suppressed the reprogramming induced by ERK inhibition and negatively regulated embryonic pluripotency by inducing differentiation via upregulation of immediate early genes, such as c-Jun, c-Fos and EGR1. These data reveal that suppression of the ERK-SRF axis is an initial molecular event that facilitates iPSC formation and may be a useful surrogate marker for cellular reprogramming.