Rosen 1987.

Methods	Placebo‐controlled, randomised, within‐participants study Number of centres not stated Period of inclusion not stated
Participants	Inclusion criteria Chronic, bilateral and symmetrical, recurring eruption of yellowish sterile pustules, occurring particularly on the thenar and hypothenar eminences and/or the sole or sides of the heel Minimum duration of 6 months Non‐response to topical treatment including potent topical steroids or prompt relapse on discontinuation of steroid therapy No topical or systemic treatment of PPP except emollients 4 weeks before the start of this trial Exclusion criteria Pregnancy Kidney insufficiency Liver insufficiency Clinical situation was assessed by the same investigator (KR) before treatment (2 weeks), after 2 weeks (0 weeks), and then every 3 weeks by judging the severity of lesions on either side Baseline data: randomly allocated to etretinate 0.6 mg/kg/d (23 palms/soles) or placebo (14 palms/soles) or etretinate 0.6 mg/kg/d and PUVA therapy 3 times per week (23 palms/soles) or PUVA therapy 3 times per week (14 palms/soles) Mean age (range), years: 53 (30 to 71); 56 (39 to 71); 53 (30 to 71); 56 (39 to 71) Male/female: 7/16; 3/11; 7/16; 3/11 Mean duration of disease (range), years: 9 (0.5 to 26); 7 (0.5 to 22) Proportion of participants with psoriatic lesions elsewhere: 13/37 Withdrawal: 7 participants were lost because of adverse events (5 in the etretinate/etretinate + PUVA therapy group: reasons for ending therapy were suddenly increased light sensitivity, with development of bullae on the feet, in combination with dry and scaly dermatitis, itching, and cheilitis (2 participants); extreme dryness of the skin and mucous membranes (1 participant); pain under all fingernails after 3 weeks of etretinate treatment (no UVA to the hands), without signs of paronychia (1 participant); and thrombophlebitis on the lower leg, considered unrelated to therapy (2 participants and 2 in the placebo/PUVA therapy group). One placebo‐treated participant withdrew from the trial because he did not tolerate the psoralen tablets, and another because he could not return regularly
Interventions	Randomisation of participants to etretinate vs placebo, then for each group randomisation of 1 side (UVA irradiation or not) Intervention 1 A: oral etretinate twice per day (0.6 mg/kg/d) (23 palms/soles) Intervention 2 B: placebo (14 palms/soles) Intervention 3 C: oral etretinate (0.6 mg/kg/d) + UVA (3 times per week) (23 palms/soles) Intervention 4 D: UVA irradiation (3 times per week) (14 palms/soles) Co‐interventions: none Duration of treatment: 14 weeks
Outcomes	No primary or secondary outcome pre‐specified Four‐point scale: cleared, much improved, somewhat improved, and unchanged/worse ("Cleared" meant an excellent result with no desquamation or pustulation; erythema and slight residual infiltration were allowed. "Much improved" meant a very good result, but some residual desquamation, pustulation, and infiltration remained. "Somewhat improved" meant a substantial, easily recognised improvement) Severity score on a 4‐point scale from 0 (none) to 3 (severe) Adverse events
Notes	AB Draco, Lund, Sweden, provided the methoxsalen (Puvamet) tablets; and AB Hoffmann‐La Roche, Skärholmen, Sweden, the etretinate (Tigason) tablets
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: "The patients were allocated to treatment groups according to year of birth (even or odd)" Comment: non‐random component in the sequence generation process
Allocation concealment (selection bias)	High risk	Quote: "The patients were allocated to treatment groups according to year of birth (even or odd)" Comment: participants and investigators could foresee assignments
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "placebo‐controlled" Comment: placebo‐controlled but obvious side effects of etretinate, especially mucocutaneous side effects (dry lips and skin)
Blinding of outcome assessment (detection bias) All outcomes	High risk	Quote: "placebo‐controlled" Comment: placebo‐controlled but obvious side effects of etretinate, especially mucocutaneous side effects (dry lips and skin)
Incomplete outcome data (attrition bias) All outcomes	High risk	Quote: "7 patients were lost because of adverse events (5 in the etretinate/etretinate +PUVA group: the reasons for ending therapy were suddenly increased light sensitivity, with development of bullae on the feet in combination with dry and scaly dermatitis, itching, and cheilitis (two patients); extreme dryness of the skin and mucous membranes (one patient); pain under all fingernails after three weeks of etretinate treatment (no UVA to the hands), without signs of paronychia (one patient); and thrombophlebitis on the lower leg, considered unrelated to therapy (one patient) and 2 in the placebo/PUVA group: One placebo treated patient withdrew from the trial because he did not tolerate the psoralen tablets, and another because he could not return regularly). The number of treatment‐related dropouts in the two groups was not statistically different" Comment: more than 10% of participants dropped out and there was no ITT analysis
Selective reporting (reporting bias)	Unclear risk	Comment: no protocol found to guarantee that all planned outcomes are presented in the results