subgroups may not be possible.
BMC Musculoskelet Disord. 2012 Feb 20;13(1):23. [Epub ahead of print]
A SCN9A gene-encoded dorsal root ganglia sodium channel polymorphism
associated with severe fibromyalgia.
Vargas-Alarcon G, Alvarez-Leon E, Fragoso JM, Vargas A, Martinez A,
Vallejo M, Martinez-Lavin M.
ABSTRACT:
BACKGROUND:
A consistent line of investigation suggests that autonomic nervous
system dysfunction may explain the multi-system features of
fibromyalgia (FM); and that FM is a sympathetically maintained
neuropathic pain syndrome. Dorsal root ganglia (DRG) are key
sympathetic-nociceptive short-circuit sites. Sodium channels located
in DRG (particularly Nav1.7) act as molecular gatekeepers for pain
detection.
Nav1.7 is encoded in gene SCN9A of chromosome 2q24.3 and is
predominantly expressed in the DRG pain-sensing neurons and
sympathetic ganglia neurons. Several SCN9A sodium channelopathies have
been recognized as the cause of rare painful dysautonomic syndromes
such as paroxysmal extreme pain disorder and primary erythromelalgia.
The aim of this study was to search for an association between
fibromyalgia and several SCN9A sodium channels gene polymorphisms.
METHODS:
We studied 73 Mexican women suffering from FM and 48 age-matched women
who considered themselves healthy. All participants filled out the
Fibromyalgia Impact Questionnaire (FIQ). Genomic DNA from whole blood
containing EDTA was extracted by standard techniques. The following
SCN9A single-nucleotide polymorphisms (SNP) were determined by 5'
exonuclease TaqMan assays: rs4371369; rs4387806; rs4453709; rs4597545;
rs6746030; rs6754031; rs7607967; rs12620053; rs12994338; and
rs13017637.
RESULTS:
The frequency of the rs6754031 polymorphism was significantly
different in both groups (P = 0.036) mostly due to an absence of the
GG genotype in controls. Interestingly; patients with this rs6754031
GG genotype had higher FIQ scores (median = 80; percentile 25/75 =
69/88) than patients with the GT genotype (median = 63; percentile
25/75 = 58/73; P = 0.002) and the TT genotype (median = 71; percentile
25/75 = 64/77; P = 0.001).
Discussion: ...Although no causality could be derived from the present
investigation; these preliminary results raise the possibility that
some patients with severe FM may have a DRG sodium channelopathy.
We are not aware of previous studies looking at SCN9A sodium channels
gene variation in FM. However; Reimann et al. studied several SCN9A
polymorphisms in patients with different painful syndromes; including
osteoarthritis; sciatica; amputee phantom pain; spine surgery and
pancreatitis. They found a link of rs6746030 with pain intensity. They
did not study the SNP rs6754031 that we found associated to FM
severity [6]. On the other hand; in
our study; rs6746030 did not differentiate FM patients from controls.
Evidence emerging from these two studies suggests that in different
painful conditions; including FM; pain perception may be linked to
dorsal root ganglia/sympathetic ganglia sodium channels gene
variations.
CONCLUSION:
In this ethnic group; a disabling form of FM is associated to a
particular SCN9A sodium channel gene variant. These preliminary
results raise the possibility that some patients with severe FM may
have a dorsal root ganglia sodium channelopathy.
PMID: 22348792 [PubMed - as supplied by publisher]
The full study can be read here:
http://www.biomedcentral.com/1471-2474/13/23/abstract
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