Prozone phenomenon in a case of active syphilitic uveitis with hypopyon Tatsushi Kawaguchi 1 , Masaharu Mizuno 1 , Yuka Onishi 1 , Taiju Ito 1 , Mari Goto 1 , Noriko Ozaki 1 1Department of Ophthalmology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital pp.869-874
Published Date 2020/7/15
DOI https://doi.org/10.11477/mf.1410213617
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Abstract Purpose:To report a case of the prozone phenomenon in active syphilitic uveitis with hypopyon.

Case:A 30-year-old man presented with one-month history of floaters and impaired vision in the right eye.

Findings:Corrected visual acuity was counting fingers in the right eye and 1.5 in the left. Severe inflammation with ciliary injection and hypopyon was observed in the right eye. The fundus was not visible due to dense vitreous opacity. Serologic testing for syphilis revealed positive for T. pallidum latex agglutination(TPLA)test with 98.4 U, and rapid plasma reagin(RPR)test with 3.1 R.U. The low values of serum TPLA and RPR seemed incompatible with the active inflammation in the eye. Serum tests repeated using diluted specimen showed high values in TPLA with 51,624 U and in RPR with 1,974 R.U. The falsely lowered values in the first test turned out to be prozone phenomenon, resulting from excess antigen in a serum sample that inhibited the antigen-antibody interaction.

Conclusion:Prozone phenomenon may occur in patients with active syphilitic uveitis. Ophthalmologists need careful interpretation with the results of serologic testing for syphilis.

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