Case Report: Blau Syndrome With Thrombocytopenia.

We report a case of Blau syndrome in a 22-year-old Chinese female. The patient initially presented with joint swelling and pain at the age of one, subsequently developing a generalized rash and uveitis. Initially diagnosed with juvenile idiopathic arthritis, she was treated based on this diagnosis. However, genetic testing conducted in 2020 revealed a heterozygous mutation, C. 1538(exon 4)T > C, in the NOD2 gene (NM_022162), resulting in the substitution of methionine with threonine at position 513 of the encoded protein (p. M513T). This finding led to the re-diagnosis of Blau syndrome. The patient exhibited intermittent hemorrhagic lesions on the skin of both lower extremities on three occasions-in 2011, 2022, and 2024-and was subsequently diagnosed with severe thrombocytopenia upon hospitalization. Analyzing and summarizing this case can provide valuable insights into the clinical characteristics of Blau syndrome, thereby contributing a deeper understanding of this rare condition.