Epidermolysis bullosa (EB) is a rare, heterogeneous genodermatosis characterized by skin fragility due to inherited defects in genes encoding proteins that maintain epidermal-dermal integrity. The severity and complications of EB vary by subtype, and no cure currently exists. The epidemiology is unknown in South Africa. This prospective observational study in KwaZulu-Natal correlated African Zulu EB patients' phenotypic features with genotypic and histological findings. Whole-exome sequencing, electron microscopy, and immunofluorescence mapping were used to identify EB subtypes. Fourteen of the 15 patients recruited initially were confirmed to have EB, while one was excluded due to poor clinicopathological-genetic correlation. Junctional EB (JEB) was identified in 11 patients, with 10 cases linked to a recurrent homozygous pathogenic variant in LAMB3, causing severe JEB, and one to ITGA3 with an unusual variant of interstitial lung disease, nephrotic syndrome, and EB (ILNEB). Two patients had autosomal dominant EB simplex, both with heterozygous KRT14 variants, and one had dominant dystrophic EB associated with a heterozygous COL7A1 variant. Eleven patients presented during the neonatal period, with a mean survival of four weeks, highlighting a high mortality rate, especially in the severe JEB cases. The cohort exhibited a balanced sex distribution, with no clear cases of consanguinity observed. JEB, with a recurrent pathogenic variant in LAMB3, emerged as the predominant subtype among African Zulu patients, underscoring the critical need for early diagnosis and tailored management strategies in resource-limited settings. Integrating clinicopathological and genetic data is essential for accurate diagnosis and prognosis, emphasizing the importance of advanced diagnostic tools in improving outcomes for EB patients in South Africa.

Integrin α3β1 is a cell adhesion receptor widely expressed in epithelial cells. Pathogenic variants in the gene encoding the integrin α3 subunit ITGA3 lead to a syndrome including interstitial lung disease, nephrotic syndrome, and epidermolysis bullosa (ILNEB). Renal involvement mainly consists of glomerular disease caused by loss of adhesion between podocytes and the glomerular basement membrane. The aim of this study was to characterize the impact of loss of integrin α3 on human podocytes. ITGA3 was stably knocked-out in the human podocyte cell line AB8/13, designated as PodoA3-, and in human proximal tubule epithelial cell line HK2 using the targeted genome editing technique CRISPR/Cas9. Cell clones were characterized by Sanger sequencing, quantitative PCR, Western Blot and immunofluorescence staining. RNASeq of integrin α3 negative cells and controls was performed to identify differential gene expression patterns. Differentiated PodoA3- did not substantially change morphology and adhesion under standard culture conditions, but displayed significantly reduced spreading and adhesion when seed on laminin 511 in serum free medium. Gene expression studies demonstrated a distinct dysregulation of the adhesion network with downregulation of most integrin α3 interaction partners. In agreement with this, biological processes such as "extracellular matrix organization" and "cell differentiation" as well as KEGG pathways such as "ECM-receptor interaction", "focal adhesion" and the "PI3K-Akt signaling pathway" were significantly downregulated in human podocytes lacking the integrin α3 subunit.

ILNEB (interstitial lung disease, nephrotic syndrome, epidermolysis bullosa) syndrome is caused by ITGA3 mutations. Demises usually happened at infancy. This study reports a complete ILNEB syndrome child with slow disease progression. Clinical data and related specimens were collected. Genomic DNA was extracted for genetic sequencing. Integrin α3 expression was detected by western blotting and immunofluorescence staining. The patient was male. He experienced recurrent rashes shortly after birth. His sparse eyebrows and eyelashes gradually lost. The patient was vulnerable to respiratory infections and had recurrent fever after vaccine immunization after 4 years. He was found with nephrotic syndrome and polycystic renal dysplasia at 8 years and progressed to end-stage renal disease at 12 years. A chest Computed Tomography revealed intestinal lung disease at 8 years. Continuous oxygen supplementation was needed at 13 years. Counts of lymphocyte subsets revealed elevated percentage of double-negative T cells and activated T cells. Next-generation sequencing revealed a novel homozygous splice mutation c.2219 + 4A > Cin ITGA3 that was predicted to be deleterious. The mutation resulted in exon17 skipping with the loss of 80 bp in the mRNA. The aberrant integrin α3 mRNA level was lower compared to the healthy control. Integrin α3 protein was not detected in urine epithelial cells and skin of the patient. We report a patient harboring a novel ITGA3 homozygous splice mutation who presented with complete ILNEB syndrome but slow disease progression. Immune disorders were suspected.

Interstitial Lung disease, Nephrotic syndrome and Epidermolysis Bullosa, also referred to as ILNEB syndrome is an extremely rare autosomal recessive condition, caused by pathogenic variants in ITGA3. 11 patients have previously been diagnosed with ILNEB syndrome of whom 7 died in infancy or early childhood. We report the only patient with ILNEB syndrome who survived past adolescence, partly due to a double lung transplant. Additionally, our patient showed oral, nasal and gynecological symptoms not previously reported in patients with ILNEB syndrome.

Integrin α3β1, a major epidermal adhesion receptor is critical for organization of the basement membrane during development and wound healing. Integrin α3 deficiency leads to interstitial lung disease, nephrotic syndrome and epidermolysis bullosa (ILNEB), an autosomal recessive multiorgan disease characterized by basement membrane abnormalities in skin, lung and kidney. The pathogenetic chains from ITGA3 mutation to tissue abnormalities are still unclear. Although integrin α3 was reported to regulate multiple extracellular proteins, the composition of the extracellular compartment of integrin α3-negative keratinocytes has not been resolved so far. In a comprehensive approach, quantitative proteomics of deposited extracellular matrix, conditioned cultured media as well as of the intracellular compartment of keratinocytes isolated from an ILNEB patient and from normal skin were performed. By mass spectrometry-based proteomics, 167 proteins corresponding to the GO terms "extracellular" and "cell adhesion", or included in the "human matrisome" were identified in the deposited extracellular matrix, and 217 in the conditioned media of normal human keratinocytes. In the absence of integrin α3, 33% and 26% respectively were dysregulated. Dysregulated proteins were functionally related to integrin α3 or were known interaction partners. The results show that in the absence of integrin α3 ILNEB keratinocytes produce a fibronectin-rich microenvironment and make use of fibronectin-binding integrin subunits αv and α5. The most important results were validated in monolayer and organotypic coculture models. Finally, the in vivo relevance of the most dysregulated components was demonstrated by immunostainings of skin, kidney and lung samples of three ILNEB patients.