PO:11:165 | Clinical mimicry and therapeutic challenge: A Case of Rapidly Progressive Mixed Connective Tissue Disease

Elena Maria Di Virgilio¹, Elisabetta Chessa², Valentina Ibba², Cosimina Matulli², Jessica Sorgia¹, Andrea Pace¹, Matteo Piga^1|2, Alberto Cauli^1|2 | ¹Università degli studi di Cagliari-Reumatologia, Cagliari, Italy; ²Struttura complessa di Reumatologia- AOU Cagliari, Cagliari, Italy

Background. Mixed Connective Tissue Disease (MCTD) is a rare autoimmune condition defined by anti-U1RNP antibodies and overlapping features of systemic sclerosis (SSc), systemic lupus erythematosus (SLE) and idiopathic inflammatory myopathies (IIM). It has an incidence of 3.8/100,000 and prognosis depending on predominant manifestations. We present a case of rapidly progressive MCTD with multiorgan involvement, highlighting the complexity of its clinical and therapeutic management.

Materials and Methods. A 60-year-old woman presented with sudden-onset, rapidly progressing symptoms within a two-month: Raynaud's phenomenon (RP), dysphagia, dyspnoea, cervical muscle weakness and weight loss. Physical examination revealed microstomia, microcheilia, sclerodactyly, diffuse skin thickening, alopecia and muscle weakness (MRC scale: 2/5 neck, 4/5 legs).

Results. Labs tests revealed elevated inflammatory markers, microcytic anemia, C3 54 mg/dl (>90), CPK 1087 U/L, troponin 2800 ng/ml, ANA 1:320 (speckled pattern) with anti-U1RNP (217) positivity. Moreover, capillaroscopy showed scleroderma pattern. CT of chest revealed reactive lymphadenopathy in the cervical-thoraco-abdominal area and pleural effusion. Pulmonary function testing was deferred due to the patient's severe clinical status. Elevated troponin (up to 3580) prompted serial echocardiography and cardiac MRI, which excluded myocarditis. Electromyography revealed sensory-motor axonal polyneuropathy and findings suggestive of inflammatory myopathy. Finally, cervical MRI revealed muscle inflammation while barium swallow demonstrated mild dilation of the distal esophagus and delayed gastric emptying. The patient met Kasukawa’s criteria (table1): the serological criterion, both common criteria (RP and scleredema), and seven disease-specific criteria: for SLE (lymphadenopathy, pericarditis/pleuritis), SSc (sclerodactyly and esophageal hypomotility), and myositis (muscle weakness, elevated serum CPK levels, and a myogenic pattern on electromyography). We performed a rescue therapy including methylprednisolone 125 mg/day, a lower dose than expected (1g/die) due to the renal crisis risk, Immunoglobulin (0,4 mg/kg/die x 5 days) and Rituximab 1g. Due to an intercurrent SarsCov2 infection, the second dose of rituximab was not administered, the remaining immunosuppressive therapy (Mycophenolate mofetil) was postponed, and the patient was treated with antiviral therapy using Remdesivir. Moreover, because of high-dose corticosteroid treatment and the disabling impact of the disease, the patient presented psychotic episode characterized by hallucinations, which required both antipsychotic medication and psychological support.

Conclusions. This case highlights how rapidly progressive MCTD can represent a major therapeutic and management challenge due to its acute onset, mimicking features of other connective tissue diseases and complications, arising from both the disease and treatment, such as immunosuppression-related risks (infections) and steroid-induced psychosis.