INTRODUCTION
BK virus (BKV) was first described by Gardner et al. in 1971, isolated
in the urine and urinary epithelium of a renal transplant recipient with
renal failure and ureteral
stenosis[1]. BKV is a
non-enveloped, 42 nm virus with a double-stranded circular DNA
containing 5000 bases and an icosahedral capsid from the Papoavirus
group in the Polyomaviridae
family[2]. Primary
infection is frequently seen in early childhood, sometimes with clinical
signs of upper respiratory tract infection, and is usually
asymptomatic[2]. After
the primary infection, the virus exists in a latent state in the
urogenital tract[2].
BKV seroprevalence is 80% in adults worldwide, and BKV infection is
seen in 10-60% after renal transplantation. 5% (1-10) of these
infections progress as BKV nephropathy (BKVN), and it is still a
significant problem affecting allograft survival in the post-transplant
period[3]. Alterations
in immunosuppressive (IS) treatments and diagnostic approaches lead to
epidemiological differences. The incidence of BKVN is higher in the
first two years after transplantation and risk is increased in patients
over 50 years of age, male gender, cases with high HLA incompatibility,
with multiple allograft rejection episodes, and those who receive
intensive triple IS
therapy[3]. Patients may
not show any symptoms other than impaired renal function. BKVN may
present with interstitial nephritis, ureteral stenosis, hydronephrosis,
and signs of a urinary tract infection. Progressive renal failure is
approximately 30-60% in affected
cases[2,3].
Early diagnosis of BKVN is essential. Since the disease is mostly
silent, it is recommended to regularly monitor BKV DNA in blood and/or
urine samples after
transplantation[4]. It
is recommended to reduce IS therapy in cases with BKV DNA levels above
the critical threshold and to confirm both BKVN and the presence of
concomitant rejection by performing a biopsy in patients with allograft
dysfunction[4]. The
crucial point in the treatment of BKVN is to reduce immunosuppression.
In addition, cidofovir, intravenous immunoglobulin (IVIG), quinolones,
and leflunomide therapy may be applied, but none of these treatments
have strong evidence to be
recommended[3].
The current knowledge of BKVN is mainly based on cross-sectional patient
series with small numbers of cases. The studies reporting disease
outcomes with large samples are rare in the literature. With this
retrospective study, we aimed to contribute to the literature by
analyzing our BKVN experience with the participation of transplantation
centers in all provinces of our country.