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Introduction: Transthyretin (ATTR) amyloidosis is a severe rare disease with wide range of characters without specific symptoms including the damage to the peripheral nervous system and cardiac involvement. Case report: A 60-year-old female patient represented with weakness and paresthesia in the distal parts of the lower limbs, impeding walking for 2 years. Initially, symptoms were considered as a manifestation of degenerative stenosis of the lumbar spine, decompressive laminectomy was performed but the symptoms after surgical treatment persisted. Based on data from clinical and electroneuromyographic examinations, axonal sensorimotor polyneuropathy was diagnosed. Genetic testing of the patient, her elder sister, son and daughter using the Sanger sequencing method detected a variant of the nucleotide sequence in the fourth exon of the transthyretin gene (Chr18: 29178562, rs148538950, NM_000371.3: c.G368A: p. Arg123His) in the heterozygous state. A subcutaneous fatty tissue biopsy of abdominal wall with a Congo red stain and polarized light examination revealed amyloid microdeposits, grade CR 1+ (minimal deposits), confirmed the diagnosis of familial ATTR-amyloidosis. Echocardiography revealed concentric left ventricular wall thickening with normal end diastolic size and volume, preserved ejection fraction, left atrial enlargement, pulmonary hypertension and type 1 diastolic dysfunction. Specific anti-amyloid therapy — tafamidis was prescribed. Conclusion: In patients with peripheral polyneuropathy and left ventricular hypertrophy of unknown etiology, a complex examination is necessary for the timely detection and treatment of amyloid polyneuropathy and cardiomyopathy.

Cardiac amyloidosis (amyloid cardiomyopathy) is a disease damage to the heart caused by extracellular amyloid deposition. In some cases, there may be local damage to the structures of the heart, for example, the atria; more often, heart damage is part of a systemic (generalized) pathology. Depending on the amyloid precursor protein, 36 types of amyloidosis are described, among which hereditary and acquired forms are distinguished. Cardiac amyloidosis is diagnosed 1) in the case of the amyloid infiltration in the myocardial bioptates or 2) in the case of non-cardiac amyloid deposition and the left ventricular wall thickening >12 mm without arterial hypertension and other reasons. The heart is most often affected in AL-, ATTR-, AA-, AANF-types of amyloidosis. Cardiac amyloidosis should be considered in patients with a heart failure with an unclear etiology, especially with preserved left ventricular ejection fraction, refractory to treatment, with proteinuria and CKD 4-5, in patients with idiopathic atrial fibrillation and conduction disturbances, in patients with left ventricular wall thickening of unclear etiology, low ECG voltage, unexplained arterial hypotension and pulmonary hypertension. Screening for cardiac amyloidosis should include non-invasive methods such as electrophoresis and immunofixation of blood and urine proteins, the free light lambda and kappa chains of immunoglobulins, 99Tc-DPD scintigraphy, genetic testing (if hereditary variants of amyloidosis are suspected), as well as a histological examination of biopsy samples stained with Congo red and polarizing microscopy.