title: The level of urinary α1 microglobulin excretion is a useful marker of peritubular capillaritis in antineutrophil cytoplasmic antibody associated vasculitis.
abstract: BACKGROUND
  Antineutrophil cytoplasmic antibody (ANCA) associated vasculitis affects small vessels in the kidney (i.e., arterioles, glomerular or peritubular capillaries, or venules). Although crescentic glomerulonephritis is a common histological finding, the incidence of peritubular capillaritis (PTC) or arteriolitis is unclear. Moreover, the laboratory data that reflect the degree of renal histological damage and distinguish between PTC and arteriolitis have not yet been clarified.
  
  
  METHODS
  We investigated laboratory data and histological findings from 11 patients diagnosed with ANCA-associated vasculitis (2 men and 9 women, mean age 70.3 ± 3.3 years) whose renal biopsies were performed between 2009 and 2014.
  
  
  RESULTS
  All patients were positive for myeloperoxidase (MPO)-ANCA. PTC or arteriolitis was detected in six patients (54.5 %), respectively. The only significant positive relationship between laboratory data and histological findings observed was that between levels of urinary α1 microglobulin (u-α1MG) excretion and the percentage of tubular atrophy and interstitial fibrosis (r = 0.67, p = 0.035). No significant differences in laboratory data were found between patients with or without arteriolitis. However, the levels of u-α1MG excretion were significantly higher in patients with PTC than in those without PTC (75.2 ± 19.5 vs. 15.0 ± 3.6 mg/dl, p = 0.035).
  
  
  CONCLUSIONS
  PTC or arteriolitis occurs at a high rate independently of crescentic glomerulonephritis in ANCA-associated vasculitis patients. The levels of u-α1MG excretion reflect the degrees of tubular atrophy and interstitial fibrosis. Moreover, high levels of u-α1MG excretion suggest that PTC is more likely than arteriolitis in ANCA-associated vasculitis patients.
authors.affiliation: Internal Medicine 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan. ohashi-n@hama-med.ac.jp.
authors.forename: Naro
authors.initials: N
authors.lastname: Ohashi
authors.affiliation: Internal Medicine 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Ishigaki
authors.affiliation: Internal Medicine 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Kitajima
authors.affiliation: Internal Medicine 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Tsuji
authors.affiliation: Internal Medicine 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Isobe
authors.affiliation: Internal Medicine 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
authors.forename: Takamasa
authors.initials: T
authors.lastname: Iwakura
authors.affiliation: Internal Medicine 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Ono
authors.affiliation: Internal Medicine 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Fujikura
authors.affiliation: Internal Medicine 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Tsuji
authors.affiliation: Blood Purification Unit, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
authors.forename: Yukitoshi
authors.initials: Y
authors.lastname: Sakao
authors.affiliation: Blood Purification Unit, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kato
authors.affiliation: Internal Medicine 1, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Yasuda
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000510:Alpha-Globulins / Q000652:urine*; D056648:Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis / Q000473:pathology* / Q000652:urine*; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000378:metabolism; D015415:Biomarkers; D002196:Capillaries / Q000473:pathology*; D005260:Female; D005921:Glomerulonephritis / Q000473:pathology; D006801:Humans; D007668:Kidney / Q000473:pathology; D007678:Kidney Glomerulus / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009195:Peroxidase / Q000378:metabolism; D012189:Retrospective Studies
chemical_list: D000510:Alpha-Globulins; D019268:Antibodies, Antineutrophil Cytoplasmic; D015415:Biomarkers; C016001:alpha-1-microglobulin; D009195:Peroxidase
keywords: Antineutrophil cytoplasmic antibody associated vasculitis; Arteriolitis; Necrotizing crescentic glomerulonephritis; Peritubular capillaritis; Urinary α1 microglobulin