Demystifying seronegative autoimmune pancreatitis.
BACKGROUND
Autoimmune pancreatitis (AIP) has been classified into type 1 and type 2 subtypes. Serum immunoglobulin G4 (IgG4) elevation characterizes type 1 AIP. Type 2 AIP and a subset of type 1 AIP are seronegative, i.e., have normal serum IgG4 levels.


OBJECTIVE
We compared the profiles of the three subsets of AIP to identify the unique characteristics of seronegative type 1 AIP and type 2 AIP.


METHODS
We compared the clinical profiles of 69 seropositive type 1 AIP patients, 21 seronegative type 1 AIP patients and 22 type 2 AIP patients.


RESULTS
Among type 1 AIP, seronegative group had similar clinical profiles when compared to seropositive group except that they were more likely to undergo surgical resection than seropositive patients (p = 0.001). Seronegative type I AIP patients were older (61.9 ± 13.7 vs 45.3 ± 17.4; p = 0.004), and differed in the occurrence of other organ involvement (OOI) (71.4% vs 0%; p < 0.001) and disease relapse (33.3% vs 0%; p = 0.005) when compared with type 2 AIP. All seronegative type 1 AIP patients had at least one of the following -OOI, disease relapse, and age >50 years while none of the type 2 AIP had OOI or disease relapse.


CONCLUSIONS
Seronegative and seropositive type 1 AIP patients have similar clinical profiles, which are distinct from that of type 2 AIP. Among the seronegative AIP group, patients are more likely to have type 1 AIP rather than type 2 AIP if they are older than 50 years or have OOI or disease relapse.
Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic College of Medicine, Mayo Clinic 200 First Street SW, Rochester, Minnesota 55905, USA.
Gokulakrishnan
G
Balasubramanian
Aravind
A
Sugumar
Thomas C
TC
Smyrk
Naoki
N
Takahashi
Jonathan E
JE
Clain
Ferga C
FC
Gleeson
Phil A
PA
Hart
Michael J
MJ
Levy
Randall K
RK
Pearson
Bret T
BT
Petersen
Mark D
MD
Topazian
Santhi S
SS
Vege
Suresh T
ST
Chari
D000328:Adult; D000367:Age Factors; D000368:Aged; D001327:Autoimmune Diseases / Q000145:classification / Q000276:immunology*; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000276:immunology / Q000473:pathology; D010195:Pancreatitis / Q000276:immunology* / Q000473:pathology / Q000628:therapy; D010950:Plasma Cells / Q000473:pathology; D011241:Prednisone / Q000627:therapeutic use; D012008:Recurrence
D007074:Immunoglobulin G; D011241:Prednisone