431. An insidious case of an Igg4 related disease mimic
Creators: name: Sharon Cowley1,
Publisher: name: Zenodo
Year: 2022
Subjects: Vasculitis
ANCA
Abstracts
Giant Cell Arthritis
MPA
GPA
EGPA
Takayasu
IgA vasculitis

description: <strong>Case presentation:</strong> A 57 year old man was referred to inpatient Rheumatology services for consideration of an autoimmune aetiology for a pericardial effusion noted during diagnostic workup for an acute stroke. His past medical history was remarkable for a recent admission with critical limb ischaemia secondary to popliteal aneurysm and thrombosis which required surgical intervention He also had depression, type 2 diabetes and psoriasis. In this early phase of illness he had no additional symptomatology indicative of a connective tissue disease and had no additional symptoms suggestive of vasculitis. Imaging at this time showed no evidence of vascular inflammation, thromboses or new aneurysms. His medications included apixaban, aspirin and escitalopram. He was an ex-smoker, didn’t drink alcohol and worked as a coal merchant. His father had a stroke in his 50s. Blood abnormalities included a normochromic normocytic anaemia with Hb of 12.6 (13-17g.dl), a monocytosis of 3.04 (0.15 – 1.3 x 10^9), ESR of 52 (0-10mm/hr) and CRP of 28.4(0-5mg/l). <strong>Diagnostic Testing:</strong> MRI brain confirmed brainstem stroke. TTE revealed an incidental large pericardial effusion of 2.5cm which evolved into tamponade requiring pericardiocentesis with drainage of 750mls of exudative effusion. Cardiac MRI showed no evidence of pericardial thickening or definitive enhancement. PET scan was completed which did not show any abnormal uptake. Temporal artery biopsy showed no evidence of arteritis.An extensive autoimmune and infectious blood work up was completed. His quantiferon was strongly positive. IgG and IgA were elevated at 19.48(6-16g/l) and 6.59 (0.6-4.0g/l). Igg4 subclass was the upper limit of normal at 0.82 (0.039 – 0.864g/l) with a low C3. While TB cultures from pericardial fluid were sterile, the infectious diseases service commenced quadruple anti-tuberculous therapy. During follow up he developed a recurrent pericardial effusion necessitating pericardiectomy. Histology showed an acute lymphocytic process with organising fibrinous reaction. He was re-referred to Rheumatology due to severe anterior knee pain which left him wheelchair bound. Knee Xray and MRI were normal. Repeat CT TAP demonstrated pericardial thickening, perinephric fat stranding and subtle mural enhancement of his infra-renal aorta. He was commenced on methotrexate and oral steroid therapy with modest result for presumed Igg4 disease. Leflunomide 20mg OD was added. Symptoms progressed and rituximab was given but he relapsed after a few months of modest benefit. Due to ongoing knee pain a NM bone scan was performed which showed focally intense radiotracer uptake in the proximal left fibula. CT TAP was again repeated which demonstrated an increase in size of the periaortic inflammatory change, now amenable to biopsy. A retroperitoneal soft tissue biopsy revealed a histiocytic neoplasm with BRAF V600E mutation consistent with Erdheim-Chester disease. <strong>Differential Diagnosis:</strong> Igg4 disease was strongly considered given the perinephric stranding, borderline Igg4 subclass levels and pericardial involvement. TB, vasculitis and malignancy were also exlcuded. Erdheim-Chester disease was finally diagnosed with classic histology. <strong>Management:</strong> Initial management with steroids, methotrexate, leflunomide and subsequently rituximab was justified in the context of a patient with significant systemic symptoms and multiple relapses. Definitive management by haematology was first line treatment with pegylated interferon 135mcg s/c weekly and dexamethasone. He failed this treatment and moved onto second line treatment with vemurafinib 480mg BD. He still uses mobility aids but has had no further disease progression to date. <strong>Conclusions: </strong>Erdheim-Chester disease is a very rare multisystem disorder that can present in a similar fashion to many rheumatological diseases including large vessel vasculitis. In patients that fail to respond or follow an atypical clinical course re-imaging and repeated re-evaluation is of critical importance in reaching the diagnosis <strong>Disclosures: </strong>None