End-stage renal disease (ESRD) contributes to the increasing prevalence of herpes zoster.

Sir,

Varicella-zoster virus (VZV) causes two clinically distinct diseases: varicella (chickenpox) and herpes zoster (HZ; shingles). The lifetime cumulative incidence is ∼10–20% of the population [1]. The incidence rates progressively increase with age, presumably owing to decline in the VZV-specific cell-mediated immunity [2]. Age is the most important risk factor for the development of HZ; however, immunocompromised patients such as transplant recipients, patients receiving selective immunomodulatory therapy and HIV-infected patients have an increased risk of VZV reactivation [3,4]. Further, immunosuppressed individuals with HZ exhibit a significantly higher rate of complications (e.g. dissemination of the disease and ocular involvement) [5].

Patients who have end-stage renal disease (ESRD) with uraemia exhibit an impaired host immune response. The reported immunological abnormalities in ESRD patients include decreased phagocytic function of granulocytes and monocytes/macrophages, defective antigen presentation by monocytes/macrophages, reduced antibody production by B lymphocytes and impaired T-cell-mediated immunity [6]. Physicians working in dialysis facilities generally presume that ESRD contributes to the increase in the prevalence of HZ. Despite this presumption, the morbidity of HZ in ESRD has not been previously reported.

This retrospective study includes information on all septuagenarian patients who visited the outpatient clinic of the nephrology division and dialysis centre affiliated to our university. A total of 220 patients were followed up for at least 3 years within the last 3.5 years. Of these 220 patients, 45 were excluded from this study because they exhibited one or more already identified risk factors for HZ (e.g. corticosteroid and/or immunomodulatory therapies, carcinomas and autoimmune disorders). Potential patients were identified by searching the diagnostic and billing codes of hospital records. If HZ was confirmed in a patient, the medical records were reviewed to verify that the case of HZ was indeed a new one. Our results revealed that the incidence of HZ increased with the progression in the stages of chronic kidney disease (CKD) (Table 1, Figure 1). In fact, the incidence rate of HZ was 84.8 per 1000 person-years in our outpatients undergoing haemodialysis or continuous ambulatory peritoneal dialysis. However, in patients with CKD stage 1, 2 or 3, the incidence rate (8.2 per 1000 person-years) was as low as that in septuagenarian HZ patients without kidney disease [5]. Diabetic nephropathy is the most important cause of ESRD that requires renal replacement therapy. Diabetes as well as CKD is a risk factor for some infectious diseases because these conditions result in a compromised immune system. However, the incidence of HZ and diabetes was not found to be significantly related as determined by the examinations performed in our hospital followed by analysis with the chi-square test.

Table 1

The number of patients per group and their gender, classified according to their CKD stage

	Number of patients (male/female)
CKD stage	Average age	With HZ	Without HZ	Total
1–3	73.78	0/2	38/41	81
4 and 5	74.21	3/1	22/13	39
5D (ESRD)	72.89	4/4	26/21	55
		7/7	86/75	175

Fig. 1

The graph shows the incidence (%) of HZ in patients classified by chronic kidney disease (CKD) stage.

We concluded that ESRD, which requires renal replacement therapy, may contribute to the increased prevalence of HZ.

Conflict of interest statement. None declared.