149 - A CASE OF KAWASAKI DISEASE THAT SHOWED BLEEDING TENDENCY WITH SEVERE THROMBOCYTOPENIA

Background：The frequency of thrombocytopenia is approximately 2% in KD, however, the case exhibiting a bleeding tendency requiring platelet transfusion is extremely rare.

Patient report: A 1-year-8-month-old boy presented with prolonged high fever, and the six main symptoms of KD were observed on the fourth day of illness.  He was then admitted to the previous hospital where he received single dose of 2g/kg IVIG and oral aspirin. While fever declined the day after treatment, it recurred on the sixth day of illness. Platelet count was suddenly decreased to 64,000 /µl on the sixth day and to 17,000/µl on the seventh day, prompting his transfer to our hospital. Covid-19 test was negative, and there was no history of Covid-19 infection. Ferritin levels were 79ng/ml, 2 blood cell lines were normal, and although serum IL-18 levels were elevated (1139 pg/ml) and the D-dimer level showed a slight elevation, tests for both HLH/MAS and vasculitis were negative. The Immature Platelet Fraction (IPF) was normal, indicating normal platelet-producing ability. The etiology was unknown, but thrombocytopenia may have been due to an allergic reaction to the IVIG or an immune thrombocytopenia (ITP)-like immune response. Intravenous prednisolone 2 mg/kg/day was initiated. The platelet count declined to 1000/µl on the eighth day , prompting platelet transfusion due to gingival bleeding. Platelet count reached 3000/µl on the tenth day , but  another platelet transfusion was required due to nasal bleeding. Platelet levels increased steadily after 11 days of illness, normalizing by the 14th day. CRP levels were 1.45 mg/dl on admission to our hospital, becoming negative by day12. Prednisolone was tapered to 0.5mg/kg/day, and upon confirming that the platelet count did not decrease, the patient was discharged on day 21 without CA dilatation. Oral administration of prednisolone was completed by day 37, and thrombocytopenia has not been observed 7 months after onset.



Conclusion:  Platelet transfusion was not effective in this case, raising suspicion of an ITP-like condition associated with thrombocytopenia. The etiology of thrombocytopenia remains unknown, however, increased production of endogenous autoantibodies triggered by the onset of KD or exogenous antibody from IVIG infusion may have contributed to the severe decline in platelet count.