This study was supported by Principia Biopharma Inc., a Sanofi company. Conflicts of interestConflicts of interest statements can be found in the Appendix. Data availabilityQualified researchers may request access to patientlevel data and related documents (including, e.g., the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications). Patientlevel data will be anonymized, and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at https://www. clinicalstudydatarequest.com.

We describe a novel mutation in PSTPIP1 resulting in pyoderma gangrenosum, acne and ulcerative colitis. This novel constellation of clinical manifestations, which we term 'PAC syndrome', suggests the need to regroup all PSTPIP1-associated phenotypes under one aetiological group.

IgA pemphigus (IGAP) is a rare, distinct variant of pemphigus, currently classified, depending upon the histological features, immunofluorescence staining pattern and autoantibody profile, into two types: subcorneal pustular dermatosis (SPD) and intraepidermal neutrophilic IgA dermatosis. In a patient with a widespread blistering disease of the skin resembling SPD-type IGAP, we demonstrate the coexistence of IgA reactivity to both epidermal (desmocollins 2 and 3) and basement membrane-associated (BP180) proteins, suggesting the coexistence of atypical IGAP and linear IgA bullous dermatosis, respectively. This case, together with 20 previous reports of atypical IGAP, underscores the limitations of current classification schemes. Therefore, we suggest reclassifying these cases under the general term 'IGAP spectrum'.

Pityriasis rubra pilaris (PRP; MIM 173200) is an uncommon papulosquamous inflammatory dermatosis. Only a few cases of PRP associated with an underlying malignancy have been documented. We investigated a 59-year-old patient presenting with a fulminant form of PRP recalcitrant to systemic retinoid therapy, in whom the skin disease heralded a diagnosis of cholangiocarcinoma. We searched the MEDLINE database to find articles reporting on similar associations of PRP with malignancies. We identified 10 studies linking PRP and malignancies, but an association between PRP and cholangiocarcinoma has not yet been reported.