A study published in the November issue of Journal of Pain1 is the first to examine the nature of pain occurrence and its characteristics in patients with transthyretin-related familial amyloid polyneuropathy (TTR-FAP). The findings suggest that pain either does or does not occur from the outset, and that its presentation changes with disease progression.
TTR-FAP is a relentlessly progressive and ultimately fatal form of amyloidosis.2 Though considered a small-fiber predominant polyneuropathy, TTR-FAP is not always accompanied by pain.
In an effort to explain the conundrum through pathophysiological mechanisms, researchers compared 2 groups of 16 patients with either painless or painful TTR-FAP treated at Henri Mondor University hospital in Créteil, France.
Results revealed that the presence or absence of pain had no impact on disease course or nerve fiber degeneration. Moreover, the 2 groups did not differ on any clinical or neurophysiologic variable, including laser evoked potential (LEP) recording and quantitative sensory testing.
“This result was unexpected, especially because small-fiber involvement is usually considered at the origin of pain in patients with peripheral neuropathies,” researcher Jean-Pascal Lefaucheur, MD, told Clinical Pain Advisor, noting that the findings imply the presence of other factors.
“Further research is needed to explain why a given type of small fiber peripheral neuropathy, such as TTR-FAP, based on a homogeneous pathophysiology of genetic origin, can be either painful or painless, according to different patients,” Dr. Lefaucheur added.