Gamma Delta T Cell Subset V Gamma 2+ Expansion Associated with Longterm Infliximab Treatment in a Patient with Ankylosing Spondylitis

To the Editor: Tumor necrosis factor inhibitors (TNFi) are widely used for the treatment of ankylosing spondylitis (AS), with infliximab (IFX) being approved by the US Food and Drug Administration for AS in 2004. Adverse event rates remain low for IFX, with risk of infection being the primary concern. IFX is accompanied by a black box warning highlighting reports of T cell lymphoma in young male patients with inflammatory bowel disease (IBD). These are often rare γδ T cell lymphomas occurring in the setting of concomitant immunosuppressive therapies1. The patient, an HLA-B27+ white man, first developed back pain at the age of 19 following an episode of trauma. He was diagnosed with AS at 23 and started treatment with IFX (5 mg/kg/6 weeks) in 2003 in addition to naproxen (1000 mg/day). This patient had no comorbidities. February 2015 radiographs documented fusion of the sacroiliac joints (modified New York criteria grade 4) and spinal ankylosis (modified Stoke Ankylosing Spondylitis Spine Score = 72). He has had sustained symptomatic response to IFX with the Bath Ankylosing Spondylitis Disease Activity Index consistently < 4. Routine clinical laboratory tests revealed an asymptomatic, afebrile inflammatory event in 2010. This was reflected in an abrupt elevation in erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP; Figures 1A–B), with an elevation in neutrophils and monocytes (Figures 1C–D). Thorough clinical evaluation revealed no evidence for antecedent infection and therefore no grounds for culture testing. Fecal calprotectin was not measured because colitis was not suspected. For these reasons, elevated CRP/ESR was viewed as an AS flare. Following this event, the patient’s lymphocyte count exceeded normal levels (Figure 1E). This lymphocytosis persisted, prompting us to define its cellular nature. Figure 1. Lymphocytosis following an inflammatory flare in a male patient with AS … Address correspondence to Professor R.D. Inman, Toronto Western Hospital, 5th Floor 5KD412, 60 Leonard Ave., Toronto, Ontario M5T 2S8, Canada. E-mail: Robert.Inman{at}uhn.ca

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