Rare presentation of antisynthetase syndrome complicated by myocarditis resulting in sustained ventricular tachycardia

Background

Antisynthetase syndrome (ASS) is a rare heterogeneous entity that is characterised by multi-organ involvement.1 Its variable systemic manifestations include myositis, interstitial lung disease (ILD), arthritis, fever, Raynaud’s phenomenon, hyperkeratotic skin changes and the presence of antibodies against amino acyl-transfer(t)-RNA synthetases.1 2 The presence of antisynthetase antibodies are important diagnostically, however, are not routinely tested and may mislead clinicians if negative. These antibodies are directed against enzymes that attach amino acids to their associated tRNA during polypeptide synthesis.3 The most frequently occurring antisynthetase specific antibody is anti-Jo-1 which is directed against the histidyl-tRNA synthetase. An anti-Jo-1 antibody is only one of the eight which have been identified.4

Case presentation

A 66-year-old non-smoking woman, originally of Jamaican descent, was initially seen in accident and emergency with a 2-week history of general malaise, cough and fever. The patient stated that over a period of 2 months it had become more difficult to carry out activities of daily living. From playing tennis three times a week, she was now using a stick to walk due to lethargy and muscle weakness. Basic investigations done in accident and emergency such as chest X-ray and blood test showed bilateral changes on chest X-ray and slightly raised inflammatory markers. The patient was discharged home with oral antibiotics and steroids with a suspected diagnosis of bilateral pneumonia. Unfortunately, no follow-up arrangements were made and sputum for culture and sensitive or atypical pathogens was not sent. The patient was then admitted 1 week later with collapse. The patient reported ongoing symptoms of significant weight loss, approximately 15 kg in 2 months, fatigue, generalised weakness, generalised joint aches, dysphagia, cough and fever. A formerly active 66-year-old with no prior medical history was now having to use a zimmer frame to mobilise. On further questioning, the patient had no prior medical history, no drug history, did not drink alcohol and had no significant family history. The patient had recently returned from Jamaica where she stayed for part of the year.

On clinical examination, the patient was a tall muscular woman with evidence of weight loss. The patient was febrile with normal blood pressure, heart rate and respiratory rate with fine crackles auscultated on her lungs. There was also oral candida. Neurological examination revealed normal cranial nerve examination with weakness of the proximal muscles of the upper and lower extremities. There was no fatiguing, fasciculations or increased tone noted and reflexes and sensation were normal throughout.

Investigations

Chest X-ray revealed bilateral lower lobe consolidation, which was treated as community-acquired pneumonia with local policy antibiotics (figure 1). Despite antibiotic therapy, there was ongoing intermittent fevers, progressive exertional dyspnoea and a non-productive cough. A high-resolution CT chest was ordered which showed diffuse ground-glass opacities and consolidations bilaterally (figure 2). This was diagnosed as non-specific interstitial pneumonia.

No growth was detected in cultures or respiratory secretions. Viral infection of hepatitis A, B, C, HIV, cytomegalovirus and Epstein-Barr virus was excluded by negative serology. A positive serum angiotensin-converting enzyme (ACE) and Anti-Sjögren's-syndrome-related antigen A (SSA, also called anti-Ro) antibody screen and raised erythrocyte sedimentation rate were noted and the rheumatology team was consulted. Antinuclear antibody (ANA), rheumatoid factor and infection screens were negative. Anti-Jo-1 antibody was also negative and it was thought not to be an autoimmune condition. A diagnosis of exclusively ILD was pursued; however, the patient deteriorated further.

ECG on admission showed a left bundle branch block with multiple frequent ventricular ectopics. Echocardiogram was largely normal with a 0.5 cm pericardial effusion, which was not thought to be significant. The morphology on the ECG changed to trigeminy and then bigeminy within a period of 24 hours. The patient reported intermittent palpitations, the morphology of which was not captured, as the patient was not on telemetry. The patient then had an episode of sustained ventricular tachycardia (VT). The episode lasted 45 min and the patient was successfully cardioverted chemically. Electrolytes were normal and the patient was subsequently managed in coronary care unit. The patient had an inpatient cardiac magnetic resonance (CMR), which showed normal left ventricular (LV) size and LV systolic function with a normal ejection fraction, however, showed an inflammatory picture that could represent myocarditis (figure 3). The findings of the CMR and the chronically elevated troponins made a diagnosis of an inflammatory process more likely and the patient was then investigated for rarer antisynthetase specific antibodies. The patient was found to be anti-PL-12 antibody positive.

Treatment

The patient was started on high-dose steroids with good clinical response. It is important to also note that the patient’s symptoms, palpitations due to frequent ectopics, worsened after an attempt to reduce steroid treatment was tried. Due to two further admissions to accident and emergency with palpitations and light-headedness steroid dose was increased and these symptoms subsided. The patient has now been referred to a specialist centre for high-dose intravenous methylprednisolone, mycophenolate mofetil and intravenous rituximab treatment. The patient will have annual CMRs as surveillance and regular echocardiograms.

Outcome and follow-up

The patient is stable clinically and has not presented to emergency services in the last 6 months. Unfortunately, this patient is now in sheltered accommodation from an independent life; however, she is still managing to do all activities of daily living independently. This patient has a regular follow-up with the ILD clinic, rheumatology and cardiology on a 3-monthly basis.