Comment
Ryan et al3 noted in a report on research gaps in psoriasis that studies are needed to validate frequency and characteristic factors associated with spontaneous remission for different phenotypes of psoriasis, including disease severity, patient age, morphologic attributes of plaques, and comorbidities. Our analysis attempts to bridge this gap in reference to type, specifically GP, and factors associated with development of chronic PP.
Our study showed that 20 of 79 patients (25.3%) with GP went on to develop chronic PP. The incidence is slightly lower than in prior smaller studies from Korea and England, which reported incidence rates of 38.9% and 33.3%, respectively.1,2 Although Ko et al1 noted that a younger age of onset was more frequently found in the cohort with complete remission of GP, this finding was not observed in our study. Although only a minority of patients underwent a molecular probe for streptococci, of those who were tested and had positive results, they were significantly less likely to develop chronic PP (P=.0177). This finding supports the classic teaching that GP originates after an episode of a streptococcal infection. Of those who developed PP, only one-fourth had been tested for streptococci via molecular probe and all were negative. Interestingly, there was no difference noted in those that had ASO titers drawn (P=1.0000). Although the data were too low to achieve statistical significance, this finding contrasts with Ko et al1 who reported that a high ASO titer correlated with a good prognosis (ie, GP did not evolve into PP). There was no difference in the likelihood of developing PP seen in patients that were treated with antibiotics (P=.1651), suggesting that obtaining a molecular probe that is positive for streptococci may be predictive of prognosis (ie, resolution) and thus is a reasonable diagnostic test to obtain. We do recognize that nonpharyngeal sources for streptococci may occur (ie, perianal), but these data were not captured in our patient population.
In our study, patients were more likely to develop chronic PP if they had a GP history that was longer than 12 months. Ko et al1 also showed that GP patients who did not develop PP were typically cleared after 8 months. There were no statistical differences noted when comparing the different treatments used to treat GP. It appears that the rapidity with which the episode clears is more predictive than the method used to clear it.
There were several limitations to this study including the small number of patients, the median 5-year follow-up time, and the retrospective design.
Conclusion
Based on our cohort study, we have concluded that GP evolves into chronic PP in approximately 25% of cases. Obtaining a group A streptococcal molecular probe or culture may serve as a prognostic tool, as physicians should recognize that GP flares associated with a positive result indicate a favorable prognosis. Additionally, GP flares that resolve within the first year of an outbreak, regardless of treatment choice, are less likely to be followed by chronic PP.
