Functional tests assessing small fiber damage could reflect clinical symptoms of patients with hereditary transthyretin amyloidosis with polyneuropathy (hATTR-PN), according to a new study published in Amyloid.

“These findings support the usefulness of functional tests as diagnostic tools in patient follow-up, also due to their non-invasiveness, easy implementation and repeatability over time,” the authors concluded.

Quantitative sensory testing and Sudoscan parameters correlated with neuropathic pain and autonomic symptoms. The authors also found an association between neuropathic pain and the sensory loss profile, which was identified as the most frequent sensory profile in quantitative sensory testing.

Cold and warm detection thresholds (CDT and WDT) were abnormal in half of patients, with values being higher in patients with neuropathic pain than in those without. Both CDT and WDT correlated with the Neuropathic Pain Symptoms Inventory (NPSI) questionnaire score. Moreover, NPSI correlated with age and Polyneuropathy Disability Scoring System (PND) staging.

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Regarding the outcome variables related to autonomic small nerve fibers, the Composite Autonomic Symptom Score questionnaire (0–31), also known as COMPASS-31, correlated with disease duration and PND staging. Most patients (57%) had abnormal foot electrochemical skin conductance (FESC), which was found to be correlated with the COMPASS-31 autonomic score.

On the other hand, intraepidermal, piloerector muscle, and sweat gland nerve fiber density quantification were not correlated with neuropathic pain or autonomic symptoms.

Most patients (60%) suffered from distal neuropathic pain. The most frequently reported type of pain was pin-and-needle paraesthesia, followed by burning and paroxysmal pain, squeezing pain, pressure pain, and dynamic mechanical allodynia. In addition, all patients experienced at least 1 autonomic symptom, with dry mouth, orthostatic intolerance, and stypsis being the most frequent.

The study included 30 patients with hATTR-PN and 25 healthy subjects. Most patients (70%) scored 1 in PND, 20% scored 2, and 10% scored 3.

Reference

Galosi E, Leonardi L, Falco P, et al. Functional and morphometric assessment of small-fibre damage in late-onset hereditary transthyretin amyloidosis with polyneuropathy: the controversial relation between small-fibre-related symptoms and diagnostic test findings. Amyloid. Published online September 12, 2022. doi:10.1080/13506129.2022.2120799