Beyond placoid: diverse clinical presentations and functional outcomes of acute syphilitic posterior placoid chorioretinopathy

Objectives: Acute syphilitic posterior placoid chorioretinopathy (ASPPC) is traditionally viewed as a uniform presentation of syphilitic posterior uveitis, though recent evidence suggests broader phenotypic variability. This study aimed to characterise ASPPC heterogeneity using multimodal imaging (MMI). Methods: Single-centre retrospective cohort study on patients presenting with syphilitic posterior uveitis or panuveitis. MMI included fundus autofluorescence (FAF), fluorescein angiography (FA), indocyanine green angiography (ICGA), and optical coherence tomography (OCT). Cases were classified as typical ASPPC when a unifocal, well-demarcated placoid lesion was present at the posterior pole, and as atypical when multifocal lesions were funduscopically occult but evident on FAF. Macular sensitivity recovery post-antibiotic treatment was evaluated in a subset of cases using microperimetry. Results: Among 33 eyes from 21 patients (median age: 51 years, 91% male), 55% had typical ASPPC and 45% an atypical presentation. HIV co-infection was found only in patients with a typical placoid lesion (42%). Both phenotypes consistently demonstrated hyperautofluorescent lesions on FAF, which corresponded to late-phase hypofluorescence on ICGA and ellipsoid zone disruption on OCT. Atypical cases showed a higher prevalence of vitritis (53% vs. 44%, P < 0.001), uveitic macular oedema (27% vs. 0%), and peripheral vascular leakage (73% vs. 28%, P = 0.004). Macular sensitivity improved by a mean of 1.7 dB/month (P = 0.005), with no significant difference observed between typical and atypical presentations. Conclusion: This study broadens the clinical spectrum of ASPPC by characterising atypical funduscopically occult presentations. Despite phenotypic differences, all cases share identical MMI features, although atypical forms may exhibit more pronounced posterior segment inflammation.