A case of familial amyloidotic polyneuropathy with a rare Phe33Leu mutation in the TTR gene

Spectrum of transthyretin gene mutations and clinical characteristics of Polish patients with cardiac transthyretin amyloidosis

BACKGROUND

Transthyretin amyloidosis (ATTR) is a rare, life-threatening systemic disorder. We present first findings on the cardiac hereditary ATTR in Poland.

METHODS

Sixty-eight consecutive patients with suspected or known cardiac amyloidosis were evaluated, including blood tests, standard 12-lead electrocardiography (ECG) and transthoracic echocardiography. ATTR was confirmed histologically or non-invasively using 99mTc-DPD scintigraphy. Transthyretin (TTR) gene sequencing was performed.

RESULTS

In 2017-2019, 10 unrelated male patients were diagnosed with hereditary ATTR. All patients had very uncommon TTR gene mutations: 7 patients had p.Phe53Leu mutation, 2 patients had p.Glu109Lys mutation and 1 patient had p.Ala101Val mutation. The age of onset ranged from 49 to 67 years (mean [SD] age, 58.7 [6.4] years). On ECG, most patients (70%) had pseudoinfarct pattern and/or low QRS voltage. The maximal wall thickness (MWT) on echocardiography varied considerably among the patients from moderate (16 mm) to massively increased (30 mm). Most patients (90%) had decreased left ventricular ejection fraction (mean [SD], 43 [11] %). On follow-up, we observed progressive heart failure in almost all cases. The first patient with p.Phe53Leu mutation died of heart failure, the second died suddenly, the third successfully underwent combined heart and liver transplant with 15 months survival from the surgery. The patient with p.Ala101Val mutation died of stroke.

CONCLUSIONS

According to available data, this is the first time that the types of TTR mutations and the clinical characteristics of Polish patients with cardiac hereditary ATTR have been described. Previous literature data about Polish background in families with p.Phe53Leu mutation and the present results, suggest that this TTR mutation might be endemic in the Polish population.

Unusual presentation of rare Phe33Leu mutation hereditary TTR cardiac amyloidosis

Introduction: Hereditary TTR cardiac amyloidosis (ATTRv-CM) is a progressive and rare autosomal dominant disease, causing the formation of insoluble amyloid fibrils that deposit in the heart and nervous tissue. Case description: The authors present a 64-year-old man who was found to have the Phe33Leu mutation causing ATTRv-CM without any neurological signs or symptoms. He presented with persistent atrial fibrillation that was refractory to anti-arrhythmic medications and multiple ablations. He was diagnosed with ATTRv-CM by a Tc-99m pyrophosphate cardiac amyloid scan. Intervention: He was treated with tafamidis, torsemide and spironolactone therapy. The patient suffered cardiac arrest and passed away. Conclusion: Clinicians should be aware of the atypical presentations of ATTRv-CM without neurological signs.

Hereditary transthyretin amyloidosis caused by the rare Phe33Leu mutation

Hereditary transthyretin amyloidosis is a rare progressive systemic disease. We describe a physically active 46-year-old man who presented with dyspnoea on exertion. An echocardiogram showed increased left ventricular wall thickness and diastolic dysfunction, but normal systolic function. The QRS voltage on ECG was normal. The patient was diagnosed with hypertrophic cardiomyopathy, and several years passed before establishment of the accurate diagnosis of hereditary transthyretin amyloidosis caused by the rare mutation ATTR Phe33Leu, previously described in only five case reports. Further investigation revealed neuropathy and nephropathy, and the patient developed severe heart failure. The patient is treated with tafamidis, has undergone heart transplantation and is currently planned for liver transplant. Hereditary transthyretin amyloidosis is likely underdiagnosed, especially in patients presenting with cardiomyopathy. A discrepancy between the left ventricular mass indicated by echocardiogram and that on ECG is an important indicator of amyloidosis, as is involvement of multiple organs.