AB0769 EROSIVE SYNOVITIS, DACTYLITIS, HYPERCALCAEMIA, LYMPHADENOPATHY, ELEVATED SERUM ACE &amp; HYPOTHYROIDISM – AN UNUSUAL PRESENTATION OF IGG4-RELATED DISEASE
Authors: E. Tranah, A. Khan, N. Bhadauria, D. Mukerjee
Journal: Annals of the Rheumatic Diseases (2021)

Background: IgG4-related disease (IgG4-RD) is a fibroinflammatory disorder which can affect almost any tissue in the body. We describe a challenging case of IgG4-RD which reflects the great heterogeneity of this disease. Objectives: A 49-year-old Mauritanian gentleman was referred to Rheumatology with chronic progressive symmetrical synovitis affecting the upper and lower limbs. He had no features suggestive of a spondyloarthropathy or connective tissue disease. Blood tests revealed a raised C-reactive peptide (CRP) of 194 mg/L and erythrocyte sedimentation rate (ESR) of 46 mm/hr. His rheumatoid factor and anti-cyclic citrullinated peptide antibodies were negative. Anti-nuclear antibody was weakly positive at 1:80 with a speckled pattern, but extractable nuclear antigen antibodies, anti-double-strand DNA-antibodies and anti-neutrophil cytoplasm antibodies were negative. Complement proteins and creatine kinase were normal. Radiographs of the hands and feet demonstrated widespread erosive changes worst at the metacarpophalangeal, metatarsophalangeal and first tarsometatarsal joints, as well as swan-neck deformities of the fifth phalanges in both hands. Chest radiograph and serological virology screen were both unremarkable. He was subsequently diagnosed with a seronegative inflammatory arthritis and treated with intramuscular methylprednisolone. He was awaiting subcutaneous methotrexate. Methods: He was hospitalised shortly after with worsening polyarthritis and hypercalcaemia (3.34 mmol/L). Examination demonstrated synovitis, new lymphadenopathy and dactylitis. Other investigations revealed a normocytic anaemia (Hb 80 g/dL, MCV 80 fL), neutrophilia (20 x 10 9 /L), eosinophilia (4 x 10 9 /L), thrombocythaemia (500 x 10 9 /L), hypoalbuminaemia (25 g/L), CRP 200 mg/L and ESR 60 mm/hr. All immunoglobulins were raised with IgG 30.5 g/L. IgG4 subset was 3.0 g/L. Parathyroid hormone was low (&lt; 0.7 pmol/L) and vitamin D was 125 nmol/L. Thyroid function, myeloma screen and blood tumour markers were unremarkable. Blood film revealed no blasts. Serum angiotensin-converting enzyme (ACE) was elevated at 171.9 U/L. A CT-chest-abdomen-pelvis revealed an enlarged thyroid with retrosternal extension and widespread lymphadenopathy above the diaphragm. Results: Biopsies of the thyroid gland and submandibular lymph node demonstrated lymphoplasmacytic fibroinflammatory changes and &gt; 40% of IgG4 cells. Neither biopsy showed evidence of sarcoidosis, tuberculosis or malignancy. He was treated with a weaning regimen of high-dose oral corticosteroids resulting in normalisation of haematological, inflammatory and biochemical parameters. His musculoskeletal pain, swelling and early morning stiffness significantly improved too. Subcutaneous methotrexate was commenced and titrated upwards to 20 mg. Two months later, his arthritis relapsed upon reduction of corticosteroids. Again, there was a marked inflammatory response with raised CRP and ESR. He had also developed a new hypothyroidism (TSH &gt; 100 mU/L, T4 0.5 µg/dL, positive TPO-antibody). Repeat hand and feet radiographs revealed severe erosive progressive disease (Figure 1). He awaits commencement of rituximab. Figure 1. Plain hand radiograph demonstrating extensive erosive arthritis. Conclusion: This is a unique presentation for a rare disease. There are few case reports of IgG4-RD causing erosive synovitis with rheumatoid-like swan-neck deformities or hypercalcaemia. Furthermore, this is the first case report as far as we know, of the disease associated with dactylitis or a raised serum ACE. Prior to biopsy, our main working diagnoses were sarcoidosis or a lymphoproliferative malignancy. The peculiar presentation necessitated a second opinion via the national IgG4-RD MDT who confirmed the histological diagnosis of IgG4-RD. We hope that this interesting case highlights the importance of histology in diagnosis of complex cases. In addition, the case presentation adds to the multitude of clinical manifestations of IgG4-RD. Disclosure of Interests: None declared