Relapsing and refractory peritoneal dialysis peritonitis caused by Corynebacterium amycolatum.

BACKGROUND: Peritonitis is an important complication and cause of morbidity in patients undergoing peritoneal dialysis (PD). Corynebacterium species, often considered skin and mucosal contaminants, are a rare cause of PD-associated peritonitis and have been acknowledged in published guidelines for the diagnosis and treatment of PD peritonitis only over the last decade. CASE-DIAGNOSIS/TREATMENT: We present two children with difficult-to-treat episodes of PD peritonitis due to Corynebacterium amycolatum. Episodes were associated with fever, abdominal pain and cloudy dialysate, high dialysate polymorphonuclear leukocyte counts, and elevated serum C-reactive protein and procalcitonin concentrations. Symptoms persisted beyond 5 days in 4 of 5 peritonitis episodes, and peritonitis relapsed despite in vitro sensitivity of the bacterial isolates to guideline-recommended antibiotics. C. amycolatum was cultured from the PD catheter tip despite 4 weeks of intraperitoneal glycopeptide therapy and clinical peritonitis resolution suggestive of efficient biofilm formation. Our systematic literature search identified three previous (adult) case descriptions of C. amycolatum peritonitis, all with repeat episodes by the same organism. The incidence of C. amycolatum as a cause of PD peritonitis has not yet been established but is likely underreported due to challenges in species differentiation. CONCLUSIONS: C. amycolatum is a rarely identified cause of refractory and/or relapsing PD peritonitis. Species differentiation of non-diphtheriae Corynebacterium isolates is critical, and prolonged antibiotic treatment, preferably with a glycopeptide antibiotic, is recommended, with a low threshold for PD catheter change or removal in case of repeat peritonitis.

Case Report: CMV-Associated Congenital Nephrotic Syndrome.

Background: Congenital nephrotic syndrome, historically defined by the onset of large proteinuria during the first 3 months of life, is a rare clinical disorder, generally with poor outcome. It is caused by pathogenic variants in genes associated with this syndrome or by fetal infections disrupting podocyte and/or glomerular basement membrane integrity. Here we describe an infant with congenital CMV infection and nephrotic syndrome that failed to respond to targeted antiviral therapy. Case and literature survey highlight the importance of the "tetrad" of clinical, virologic, histologic, and genetic workup to better understand the pathogenesis of CMV-associated congenital and infantile nephrotic syndromes. Case Presentation: A male infant was referred at 9 weeks of life with progressive abdominal distention, scrotal edema, and vomiting. Pregnancy was complicated by oligohydramnios and pre-maturity (34 weeks). He was found to have nephrotic syndrome and anemia, normal platelet and white blood cell count, no splenomegaly, and no syndromic features. Diagnostic workup revealed active CMV infection (positive CMV IgM/PCR in plasma) and decreased C3 and C4. Maternal anti-CMV IgG was positive, IgM negative. Kidney biopsy demonstrated focal mesangial proliferative and sclerosing glomerulonephritis with few fibrocellular crescents, interstitial T- and B-lymphocyte infiltrates, and fibrosis/tubular atrophy. Immunofluorescence was negative. Electron microscopy showed diffuse podocyte effacement, but no cytomegalic inclusions or endothelial tubuloreticular arrays. After 4 weeks of treatment with valganciclovir, plasma and urine CMV PCR were negative, without improvement of the proteinuria. Unfortunately, the patient succumbed to fulminant pneumococcal infection at 7 months of age. Whole exome sequencing and targeted gene analysis identified a novel homozygous, pathogenic variant (2071+1G>T) in NPHS1. Literature Review and Discussion: The role of CMV infection in isolated congenital nephrotic syndrome and the corresponding pathological changes are still debated. A search of the literature identified only three previous reports of infants with congenital nephrotic syndrome and evidence of CMV infection, who also underwent kidney biopsy and genetic studies. Conclusion: Complete workup of congenital infections associated with nephrotic syndrome is warranted for a better understanding of their pathogenesis ("diagnostic triad" of viral, biopsy, and genetic studies). Molecular testing is essential for acute and long-term prognosis and treatment plan.