Transthyretin Glu54Leu - an unknown mutation within the Swedish population associated with amyloid cardiomyopathy and a unique fibril type

Case Report: Transthyretin Glu54Leu-a rare mutation with predominant cardiac phenotype

We report two unrelated Bulgarian families with hereditary transthyretin (ATTR) amyloidosis due to a rare p.Glu74Leu (Glu54Leu) pathogenic variant found in seven individuals-three of them symptomatic. Only one family with the same variant and with a Swedish origin has been clinically described so far. Our patients are characterized by predominant cardiac involvement, very much similar to the Swedish patients. Although the initial complaint was bilateral carpal tunnel syndrome, advanced amyloid cardiomyopathy was found in two symptomatic carriers at diagnosis with heart failure manifestations. The neurological involvement was considered as mild, with mainly sensory signs and symptoms being present. We followed a non-biopsy algorithm to confirm the diagnosis. Tafamidis 61 mg has been initiated as the only approved disease modifying treatment for ATTR cardiomyopathy. Clinical stability in the absence of adverse events has been observed at follow up.

Hereditary transthyretin amyloidosis in Sweden: Comparisons between a non-endemic and an endemic region

INTRODUCTION

Hereditary transthyretin amyloidosis (ATTRv) is endemic in northern Sweden (Västerbotten). The awareness of ATTRv amyloidosis is lower in Stockholm, a non-endemic region in Sweden. The aim of this study was to compare the possible differences in diagnostic delay, disease phenotypes, treatment and survival between a non-endemic and an endemic region in Sweden.

METHODS

The in- and outpatient diagnosis registry at the Department of Neurology at Karolinska University Hospital and the Amyloidosis Centre at University Hospital of Umeå were used to identify patients between January 2006 and November 2017.

RESULTS

In total, 21 patients in Stockholm and 134 patients in Västerbotten were included. The time between symptom onset to time-point of diagnosis was significantly longer in Stockholm vs Västerbotten. This corresponded to a longer median time between first visit at amyloidosis centre to time-point of diagnosis in Stockholm vs in Västerbotten. The most common reason for a diagnostic delay was negative tissue biopsies.

CONCLUSION

There was a diagnostic-, but no patient-delay in non-endemic Stockholm vs endemic Västerbotten. Despite a more severe neuropathic phenotype in Stockholm at the onset, the systemic affection over the course of disease and of survival seems not to be influenced by the diagnosis delay in Stockholm.

Epidemiology of hereditary transthyretin amyloidosis in the northernmost region of Sweden: a retrospective cohort study

INTRODUCTION

Epidemiological data on hereditary transthyretin (ATTRv) amyloidosis from the northernmost region of Sweden (Norrbotten) are sparse.

METHODS

We reviewed the medical records of all incident cases of ATTRv amyloidosis in Norrbotten between 2006 and 2018. Official population and mortality statistics were used to estimate incidence rates and standardised mortality ratios (SMRs).

RESULTS

Ninety-three patients were diagnosed with ATTRv amyloidosis between 2006 and 2018 (median age, 72.8 years; 68.8% men; 95.7% Val30Met [p.Val50Met] mutation). The incidence rate per 100,000 persons and year increased from 1.50 (95% confidence interval [CI], 0.84-2.47) cases in 2006-2009 to 4.92 (95%CI, 3.46-6.78) cases in 2016-2018. The SMR in the ATTRv amyloidosis cohort was 2.64 times higher than in the general population in 2006-2018 (95%CI, 1.78-3.77). However, there were indications of lower SMRs over time (2006-2012, 2.96 [95%CI, 1.73-4.74]; 2013-2018, 2.32 [95%CI, 1.23-3.96]) and by use of disease-modifying drugs (no, 3.21 [95%CI, 1.87-5.13]; yes, 2.09 [95%CI, 1.08-3.64]).

CONCLUSION

The incidence of ATTRv amyloidosis increased 3-fold in Norrbotten between 2006 and 2018, most likely due to a previous underdiagnosis - with suggestions of lowered mortality during later years, possibly due to the introduction of disease-modifying drugs.