An Efficacy and Safety Study of CNTO1959 (Guselkumab) in the Treatment of Participants With Generalized Pustular Psoriasis or Erythrodermic Psoriasis

The purpose of this study is to examine descriptively the efficacy of CNTO 1959 in participants with generalized pustular psoriasis (GPP) or erythrodermic psoriasis (EP).

This is a phase 3, multicenter (when more than one hospital or medical school team work on a medical research study), open-label study evaluating the efficacy and safety of CNTO1959 (Guselkumab) in the treatment of participants with GPP or EP. Participants will receive 50 milligram (mg) guselkumab subcutaneously at Weeks 0, 4 and 12. At Week 16 up to Week 52 participants who will be defined "Very much improved" or "Much improved" in Clinical Global Impression (CGI) will continue to receive guselkumab 50 mg every 8 weeks from Week 20 to the study end (Week 52). At each visit timing from Week 20, participants who will be defined "No change" or "Worsened" will receive guselkumab 100 mg and continue 100 mg every 8 weeks dosing until Week 52. Participants who are "Minimally improved" will also receive guselkumab 100 mg only if investigator considers it necessary. Participants will primarily be assessed for the treatment success. Participants' safety will be monitored throughout the study.

Eligibility Criteria:
Inclusion Criteria:

* Have a diagnosis of generalized pustular psoriasis (GPP) or erythrodermic psoriasis (EP) at screening. A diagnosis of GPP must be classified on the basis of the criteria for diagnosis of GPP by Japanese Dermatological Association (JDA)
* Have a history of plaque-type psoriasis if subjects have a diagnosis of EP
* Have an involved body surface area (BSA) of lesion greater than or equal to (\>=) 80 percent (%) at baseline if subjects have a diagnosis of EP.
* Be a candidate for phototherapy or systemic treatment for psoriasis (either naïve or history of previous treatment)
* Before the first administration of study drug, a woman must be either not of childbearing potential or of childbearing potential and practicing a highly effective methods of birth control, consistent with local regulations regarding the use of birth control methods for subjects participating in clinical studies

Exclusion Criteria:

* Has a total score of JDA severity index for GPP \>=14 at baseline if subjects have a diagnosis of GPP
* Has a differential diagnosis of the erythroderma (exmaple (eg), erythroderma caused by lymphoma or drug eruption) other than EP.
* Has refused hospitalization though the investigator needed hospitalization
* Has body mass index (BMI) less than (\<) 18 kilogram per square meters (kg/m\^2) or meets the following modified criteria for cachexia.
* Has a BMI \< 20 kg/m\^2 and has lost more than 5% of their body weight in the previous months, and 4 out of the following are present: a) decreased muscle strength b) fatigue or reduced physical activity c) anorexia d) low muscle mass e) CRP greater than (\>) 7 mg/L 6) hemoglobin (Hb) \<12 gram per deciliters (g/dL) f) serum albumin \< 3.0 g/dL
* Has Common Terminology Criteria for Adverse Events (CTCAE) Version 4 Grade 2 or higher heart failure or CTCAE v.4 Grade 3 or higher kidney failure