The quality of evidence is downgraded by study limitations (unclear allocation concealment and lack of blinding), and by imprecise results (few patients).
A Cochrane review [Abstract] 1 included 5 studies with a total of 162 subjects aged from 12 to 77 years. Twenty-three of 162 participants had streptococcus-positive throat swab culture. Four studies assessed antibiotic treatment (penicillin, erythromycin, azithromycin, or rifampicin), and 1 study assessed the effects of tonsillectomy. Two comparisons (erythromycin compared to no treatment, and rifampicin compared to placebo) did not measure any of the outcomes of interest. Meta-analysis was not performed due to heterogeneity of participants' characteristics and interventions.Guttate psoriasis:One study (n=20) assessed penicillin (1.6 million units intramuscularly once a day) versus no treatment (6 weeks of treatment, with 8-week follow-up from start of treatment). At 6-week follow-up, no adverse events were observed in either group, and there was no statistically significant difference between in the proportion of participants with clear or almost clear skin (RR 2.00, 95% CI 0.68 to 5.85).Chronic plaque psoriasis:One study (n=50) assessed long-term azithromycin treatment (500 mg daily dose) versus vitamin C. Adverse events were reported in the azithromycin group (10 out of 30 had nausea and mild abdominal upset), but not in the vitamin C group. In the azithromycin group, 18/30 versus 0/20 participants in the vitamin C group reached Psoriasis Area and Severity Index (PASI) 75 at the end of 48 weeks of treatment (RR 25.06, 95% CI 1.60 to 393.59).One study (n=29) assessed tonsillectomy versus no treatment, with 24-month follow-up after surgery. One participant in the tonsillectomy group had minor bleeding. At 8-week follow-up, 1/15 in the tonsillectomy group, and 0/14 in the no treatment group achieved PASI 90; and 3/15 participants in the tonsillectomy group, and 0/14 in the no treatment group achieved PASI 75 (RR 6.56, 95% CI 0.37 to 116.7).
Comment: The included studies did not allow investigation into the influence of Streptococcal infection, and a key intervention (amoxicillin) was not assessed. Further studies assessing the efficacy and tolerance of penicillin V or amoxicillin are needed in children and young adults with guttate psoriasis.
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