Background/Purpose: Senile systemic amyloidosis (SSA) derived from wild-type transthyretin (TTR) is a debilitating autosomal dominant disease leading to motor disability within 5 years and fatal within a decade without treatment. It is a common condition of old individuals, especially men. The main presentation is by cardiac involvement. SSA is, however, a systemic disease, and amyloid deposits may appear in many other tissues such as cartilage and ligaments¹. Lumbar spinal stenosis is also a condition of elderly individuals in whom narrowing of the lumbar spinal canal leads to nerve compression of the lower extremities. Neuropathy caused by TTR amyloidosis had been frequently misdiagnosed as CIDP, paraproteinaemic peripheral neuropathy and other causes of acquired neuropathy².

Methods: This is a retrospective cohort study using the 2016 National Inpatient Sample (NIS) of adults hospitalized for Cardiac Amyloidosis (CA) as the admitting diagnosis and lumbar spinal stenosis (LSS) as a secondary diagnosis based on ICD-10 codes. Multivariate linear regression adjustment for confounders of age, gender and race was made. STATA 15 was used for data analysis.

Results: 1068 patients were admitted with cardiac amyloidosis in 2016, of which 90 patients had lumbar spinal stenosis (8.42%), 25 were females (27.77%), 65 males (72.2%), 65 were non-African American (72.2%) and 25 individuals were African American (27.77%). Mean age was 78.8 for those with CA and LSS, compared to 72.37 for CA and 68.3 for LSS alone. Univariate linear regression showed a significant relation between these two conditions (OR: 2.48; 95%-CI 1.49-4.12; p value: < 0.001). Multivariate linear regression adjusted to age, race and gender also showed a significant correlation (OR: 1.70; 95%-CI 1.03-2.82; p value: < 0.04). Subgroup analysis demonstrated an increased risk for developing LSS along with CA with the increase of age (OR: 1.09 per year of age; 95%-CI 1.06-1.12; p value: < 0.001) and for African-Americans (OR: 3.8; 95%-CI 1.37-10.6; p value: < 0.01). However, this association is less frequent in the female gender (OR: 0.028; 95%-CI 0.1-0.77; p value: < 0.01).

Conclusion: We conclude that LSS is quite frequent in patients with CA due to TTR-deposit therefore patients with lumbar back pain in the setting of restrictive cardiomyopathy deemed to be secondary to TTR, need a confirmatory tissue biopsy to avoid misdiagnosis because diverse treatment options are available, including tafamidis or patisiran, which all appear to be effective in early disease stages.

Table 1 Relation between Cardiac Amyloidosis and Lumbar Spinal Stenosis adjusted for age, gender and race.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/lumbar-spinal-stenosis-in-patients-with-wild-type-transthyretin-cardiac-amyloidosis/