Fredriksson 1978.

Methods	Parallel‐arm randomised controlled trial Number of centres not stated Period of inclusion not stated
Participants	Inclusion criteria Not stated Exclusion criteria Not stated Baseline data: randomised to RO 10‐9359 (25 mg thrice per day) (n = 15) or RO 10‐9359 (200 mg twice per week) (n = 15) Mean age (range), years: 47.3 (37 to 67); 45.9 (36 to 61) Mean duration of the condition (range), years: 5.6 (2 to 15); 5.9 (2 to 17) Mean number of pustules (range): 64.4 (39 to 104); 64.1 (31 to 119) Proportion of participants with psoriatic lesions elsewhere: not specified Withdrawal: no mention of missing data
Interventions	Intervention 1 A: oral RO 10‐9359 (25 mg thrice per day) (15 participants) Intervention 2 B: oral RO 10‐9359 (200 mg twice per week) (15 participants) Co‐interventions: none Duration of treatment: 8 weeks
Outcomes	No primary or secondary outcomes pre‐specified Decreased number of pustules
Notes	Funding: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "30 patients randomly allocated to two treatment groups" Comment: insufficient information about the sequence generation process to permit judgement
Allocation concealment (selection bias)	Unclear risk	Quote: "30 patients randomly allocated to two treatment groups (one group treated with etretinate 75 mg daily and the other with 200 mg twice weekly)" Comment: the method to guarantee allocation concealment is not described
Blinding of participants and personnel (performance bias) All outcomes	High risk	Comment: no mention of blinding
Blinding of outcome assessment (detection bias) All outcomes	High risk	Comment: no mention of blinding
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Comment: no mention of missing data
Selective reporting (reporting bias)	Unclear risk	Comment: no protocol found to guarantee that all planned outcomes are presented in the results