Acute Generalized Exanthematous Pustulosis Difficult to Distinguish from Pustular Psoriasis after the Use of Contrast Medium in a Patient with Psoriasis Vulgaris

<p>A 37-year-old man was admitted with fever in the 38°C range, erythema with skin flushing and scaling all over the body, and numerous needle-head-sized pustules, some of which had fused to form a sea of pus. He had a paternal history of psoriasis vulgaris and had himself suffered from the condition for 10 years. He had earlier complained of chest pain, and his creatine kinase level was high ; thus, he underwent contrast (iohexol) -enhanced computed tomography 6 days before admission. On admission, his Psoriasis Area Severity Index (PASI) score was 54.1, neutrophil count was 21,000/μL, and C-reactive protein level was 29.79 mg/dL. Bacterial culture of the pustules was negative. Histopathological examination revealed a thickened club-shaped epidermis,hyperkeratosis, and loss of the granular layer. Some neutrophil aggregations were observed under the stratum corneum, and there were many spongiform pustules. We diagnosed pustular psoriasis preceded by psoriasis vulgaris. We administered topical systemic steroids and oral etretinate capsules (30 mg/day). The rash rapidly improved, and 13 days after admission, the patient was discharged with a PASI score of 22.4. The rapid improvement of the rash suggested that iohexol may have triggered acute generalized exanthematous pustulosis (AGEP) ; thus, additional tests were performed. Iohexol drug-induced lymphocyte stimulation test was negative, the patch test was positive, and we detected no mutation in the IL36RN gene or CARD14 gene exon 2-4. The AGEP score was 10 (using the criteria of the Euro SCAR study group). He met the diagnostic criteria for both pustular psoriasis and AGEP. We diagnosed AGEP based on the rapid disease improvement and the positive patch test. We report a case for whom it was difficult to distinguish AGEP from pustular psoriasis because of the many similarities between the two conditions. Skin Research,21: 288-294,2022 </p>