Hereditary palmoplantar keratoderma (PPK) involves hyperkeratosis of the palmoplantar skin and belongs to the palmoplantar epidermal differentiation disorders (pEDDs). One causal gene is Desmoglein 1 (DSG1), which encodes a protein crucial for epidermal integrity. Monoallelic DSG1 variants cause mild, non-syndromic PPK, whereas bi-allelic DSG1 variants typically cause syndromic PPK with severe additional clinical features (SAM syndrome). Here, we report the first detection of a homozygous DSG1 variant in mild, non-syndromic PPK. Pakistani siblings presented with striate PPK, characterized by deep palmar creases and plantar fissures only. Exome sequencing revealed the homozygous DSG1 splice-site variant c.685-3T>A with familial cosegregation. In silico analyses indicated a low probability of exon 7 skipping. An exon-trap assay confirmed splicing disruption, although some wild-type (WT) transcripts were also detected. The partial retention of DSG1 WT transcripts may explain the mild phenotype. This finding highlights the phenotypic variability of DSG1-related disorders (DSG1-pEDD), related to residual DSG1 activity.

Palmoplantar keratoderma (PPK) is a heterogeneous group of disorders characterized by abnormal thickening of the skin on the palms and soles. Striate palmoplantar keratoderma (SPPK) is commonly caused by heterozygous mutations in the desmoglein-1 (DSG1) gene. This study aimed to report a case of a 36-year-old Chinese female patient with SPPK caused by a novel DSG1 gene mutation, along with her family history, and explore its potential relationship with other genetic variants. Whole-exome sequencing was performed on the patient and their family members to identify the pathogenic mutation, which was validated by Sanger sequencing. Histological and electron microscopy analyses were conducted to examine the pathological characteristics of skin tissue.of skin tissue. A frameshift mutation, c.1285del, in exon 10 of the DSG1 gene was identified, leading to a loss of protein function and resulting in SPPK. This mutation was also detected in two other family members with similar phenotypes. Additionally, a classical splicing variant, c.313+2dup, in the low-density lipoprotein receptor (LDLR) gene associated with hypercholesterolemia was identified in the patient; however, no direct association with SPPK was observed. This study was the first to report a novel mutation in the DSG1 gene associated with SPPK and suggested a potential role of the LDLR gene variant in SPPK patients, providing new insights for further research into the genetic mechanisms underlying SPPK.

PNP is a malignancy-associated autoimmune mucocutaneous syndrome due to autoantibodies against plakins, desmogleins, and other components of the epidermis and basement membrane of epithelial tissues. PNP-causing malignancies comprise mainly lymphoproliferative and hematologic neoplasms. PNP is extremely rare, especially in children. Here, we present the first case of a child who developed PNP on a PTLD after small bowel transplantation because of a severe genetic protein-losing enteropathy. The patient in this case report had a severe stomatitis, striate palmoplantar keratoderma, and lichenoid skin lesions. In addition, she had marked esophageal involvement. She had lung pathology due to recurrent pulmonary infections and ventilator injury. Although we found no evidence of BO, she died from severe pneumonia and respiratory failure at the age of 12 years. It is exceptional that, despite effective treatment of the PTLD, the girl survived 5 years after her diagnosis of PNP. We hypothesize that the girl survived relatively long after the PNP diagnosis due to strong T-cell suppressive treatments for her small bowel transplantation.