P047 Cutaneous clues to a rare diagnosis: the vasculopathic form of anti-MDA5 dermatomyositis

Abstract Introduction Anti-MDA5 associated dermatomyositis is traditionally recognised as an amyopathic subtype of dermatomyositis with multiple phenotypes, more common in Asian populations. Diagnosis can be challenging due to the absence of features more frequently associated with dermatomyositis such as a heliotrope rash and Gottron’s papules. The more commonly recognised phenotype presents with rapidly progressive interstitial lung disease. However, this case highlights an atypical phenotype with specific examination findings, helping provide greater awareness of the range of presentations. This demonstrates how a focus on history and examination in the absence of typical serological markers can support early diagnosis and improve patient outcomes. Case description A 45-year-old man from Asia presented with a six-month history of haemoptysis, myalgia, weakness, lethargy and 30kg of weight loss in 6 months. Medical history included ‘prior lung scarring’ found during tuberculosis screening. On assessment, he had profound weakness, cachexia, ankle oedema, and vasculopathic skin lesions. Neurological examination showed lower limb weakness (MRC grade 2-3), absent reflexes, and no upper motor neuron signs. Bloods on admission demonstrated a creatine kinase 358 IU/L, creatinine 33 umol/L, Albumin 15 g/L, CRP 31 mg/L, ALT 63 IU/L, ANCA negative. Further results showed two negative HIV tests and two negative quantiferon tests. Chest radiograph showed mild right sided peri-hilar and lower zone consolidation, and an urgent CT-thorax abdomen pelvis showed bilateral lower lobe opacities suggesting infection or aspiration. Dysphagia was identified, and swallow assessment deemed him unsafe for oral intake, necessitating nasogastric feeding. Risk feeding with patient consent led to respiratory deterioration, requiring high-flow oxygen and temporary admission to intensive care. Electromyography reported diffuse myositis. Once reviewed by the rheumatology team dermatomyositis returned to the differential due to the myopathy, myalgia and skin lesions. Finally, positive anti-MDA5 and anti-Ro52 antibodies confirmed anti-MDA5 dermatomyositis with cutaneous vasculopathy and severe myopathy. Induction • IV methylprednisolone (1g x 3 days) • Weaning prednisolone (1 mg/kg) • IV immunoglobulins (3 courses of 2g/kg daily for 5 days) Immunosuppression • Cyclophosphamide induction • Mycophenolate mofetil maintenance Complications • Pneumocystis PCR-positive → treated with co-trimoxazole • Chronic hepatitis B → started on entecavir Supportive Care • Short term RIG feeding • Physiotherapy • Occupational therapy • Speech and language team Following 155 days of admission, the patient was discharged on a normal diet and mobilising independently. At first review the patient had reactivation of his disease due to poor medication concordance, which remained a challenge. Though retaining independence, a reduction in mobility persisted compared to his pre-morbid baseline. Discussion Anti-MDA5 dermatomyositis can be difficult to recognise due to the absence of classic dermatomyositis features such as heliotrope rash and Gottron’s papules. The three recognised phenotypes- rheumatoid-like, vasculopathic, and rapidly progressive ILD- lack formal diagnostic criteria and established treatment guidelines necessitating a low threshold for suspicion and early involvement of rheumatology teams. This case illustrates the vasculopathic subtype, emphasising the diagnostic value of early recognition of the hyperkeratotic, punched-out, skin lesions that can be seen in up to 82% of cases. While Gottrons papules may not be evident, such lesions can emerge in areas previously affected earlier in the disease course. It is noted that the patient was never measured to have a creatine kinase higher than the admission value of 358 IU/L. Dermatomyositis was part of the early differential diagnosis, though this was not investigated further and perhaps felt to be unlikely due to the nearly normal creatine kinase. In retrospect the creatinine of 33umol/L in a young patient with marked weight loss, weakness and myalgia may describe someone who has profound clinical myopathy and myositis but no longer has the muscle mass to produce the raised creatine kinase consistent with biochemical myositis, contributing to the diagnostic challenge. The nature of myopathic dermatomyositis with normal creatine kinase compared to clinically amyopathic dermatomyositis is a topic of discussion; how both are defined and the pathophysiology of how it occurs. A further point of discussion is whether the suggested disease course of lost muscle mass spuriously lowering the creatine kinase would be disputed. Additionally, whether people would commonly recognise this phenotype of anti MDA5 dermatomyositis with vasculopathic skin lesions compared to the rapidly progressive ILD variant. Key learning points Anti-MDA5 dermatomyositis is rare and heterogeneous, requiring heightened awareness for timely diagnosis. This can be aided with appropriate history and examination even in the absence of commonly expected examination findings such as heliotrope rash or gottrons papules or biochemistry such as raised creatinine kinase. Focusing on the presence of clear clinical myopathy and weakness without a convincing neurological distribution should prompt specific?diagnostic tests such as extended myositis ENA or electromyography. Recognition of vasculopathic lesions in the context of myopathy and myalgia help diagnosis of this challenging condition. Greater awareness of the different, more indolent phenotypes that lack rapidly progressive interstitial lung disease can inform optimal management. A normal or nearly normal creatine kinase does not rule out myositis, especially when patients have low muscle mass. Dermatomyositis with or without myopathy is a complex spectrum of disease and this case suggests a disease process that may obscure early diagnosis. The goal of early diagnosis is commencement of early immunosuppression to optimise outcomes, as despite the absence of rapidly progressive interstitial lung disease in this case, there remains a risk of severe morbidity and mortality across all phenotypes.