The proteogenomic path towards biomarker discovery

The desire for biomarkers for diagnosis and prognosis of diseases has never been greater. With the availability of genome data and an increased availability of proteome data, the discovery of biomarkers has become increasingly feasible. However, the task is daunting and requires collaborations among researchers working in the fields of transplantation, immunology, genetics, molecular biology, biostatistics and bioinformatics. With the advancement of high throughput omic techniques such as genomics and proteomics (collectively known as proteogenomics), efforts have been made to develop diagnostic tools from new and to-be discovered biomarkers. Yet biomarker validation, particularly in organ transplantation, remains challenging because of the lack of a true gold standard for diagnostic categories and analytical bottlenecks that face high-throughput data deconvolution. Even though microarray technique is relatively mature, proteomics is still growing with regards to data normalization and analysis methods. Study design, sample selection and rigorous data analysis are the critical issues for biomarker discovery using high-throughput proteogenomic technologies that combine the use and strengths of both genomics and proteomics. In this review, we look into the current status and latest developments in the field of biomarker discovery using genomics and proteomics related to organ transplantation, with an emphasis on the evolution of proteomic technologies.     

Non-HLA antibodies to immunogenic epitopes predict the evolution of chronic renal allograft injury

Chronic allograft injury (CAI) results from a humoral response to mismatches in immunogenic epitopes between the donor and recipient. Although alloantibodies against HLA antigens contribute to the pathogenesis of CAI, alloantibodies against non-HLA antigens likely contribute as well. Here, we used high-density protein arrays to identify non-HLA antibodies in CAI and subsequently validated a subset in a cohort of 172 serum samples collected serially post-transplantation. There were 38 de novo non-HLA antibodies that significantly associated with the development of CAI (P<0.01) on protocol post-transplant biopsies, with enrichment of their corresponding antigens in the renal cortex. Baseline levels of preformed antibodies to MIG (also called CXCL9), ITAC (also called CXCL11), IFN-γ, and glial-derived neurotrophic factor positively correlated with histologic injury at 24 months. Measuring levels of these four antibodies could help clinicians predict the development of CAI with >80% sensitivity and 100% specificity. In conclusion, pretransplant serum levels of a defined panel of alloantibodies targeting non-HLA immunogenic antigens associate with histologic CAI in the post-transplant period. Validation in a larger, prospective transplant cohort may lead to a noninvasive method to predict and monitor for CAI.     

Frictional asymptomatic darkening of the extensor surfaces

Frictional asymptomatic darkening of the extensor surfaces (FADES), also known as hyperkeratosis of the elbows and knees, is commonly seen by dermatologists but has never been well characterized. Patients present with uniform, asymptomatic, brown darkening over the extensor surfaces of the elbows and knees with minimal scaling. Both frictional stress and family history may play a role in the pathogenesis of this condition. The results of cutaneous biopsy specimens typically reveal hyperkeratosis, acanthosis, and mild papillomatosis with minimal inflammation. Keratolytic agents such as lactic acid and urea cream along with avoiding frictional stress can be effective in the management of this condition. We describe a series of cases of FADES and its etiology and management options.     

Idiopathic red ear syndrome: A rare case report

Red ear syndrome (RES) is a very rare disorder that is characterized by a unilateral or bilateral attack of paroxysmal burning sensation and reddening of the external ear. The duration of symptoms ranges from a few seconds to hours. It can occur spontaneously or be triggered by rubbing of the ear, heat or cold stimulation, brushing of hair, and neck movement. Diagnosis and treatment of this condition are challenging. The pathophysiology of RES is still unclear and hypotheses involving peripheral or central nervous system mechanisms have been proposed. RES is regarded as refractory to medical treatments, although some migraine preventative treatments have shown moderate benefit mainly in patients with migraine‐related attacks. We report a case with Idiopathic RES who presented with paroxysmal redness of the bilateral pinnae partially benefitted by medical treatment.