Abstract
Objectives
Although pain is a common complication of the hypermobile type of Ehlers–Danlos syndrome, its underlying mechanisms are still an issue of controversy. In this psychophysical ...study, we aimed at testing small-fiber function and the endogenous pain inhibitory control in patients with pain due to Ehlers-Danlos syndrome.
Methods
In 22 patients with pain due to Ehlers-Danlos syndrome and 22 healthy participants, matched for age and sex, we tested small-fiber function using quantitative sensory testing and the endogenous pain inhibitory control using the conditioned pain modulation (CPM) protocol. As quantitative sensory testing methods, we included thermal pain and mechanical pain thresholds and the wind-up ratio. The CPM protocol consisted of two heat painful stimuli, that is, a test stimulus and a conditioning stimulus.
Results
All patients complained of widespread pain. Quantitative sensory testing revealed no small-fiber deficit; in the area of maximum pain, we found an increased wind-up ratio. Whereas in the healthy participants the CPM protocol showed that the test stimulus rating was significantly reduced during conditioning, in patients with pain due to hEDS, the test stimulus rating increased during conditioning.
Conclusions
Our psychophysical study showing that patients with pain due to hEDS have an increased wind-up ratio in the area of maximum pain and abnormal CPM protocol suggests that in this condition, pain is associated with central sensitization, possibly due to deficit of the endogenous pain inhibitory control. These data might be relevant to pharmacological treatment.
We identified two unstable variants in the third exon of α-globin genes: Hb Bernalda/Groene Hart (HBA1:c.358C>T), and Hb Caserta (HBA2:c.79G>A) in
to Hb Sun Prairie (HBA2:c.391G>C), also named Hb ...Southern Italy. These mutations occurred in the H helix of the α-globin that is involved in heme contacting, specific recognition of α-hemoglobin-stabilizing protein (AHSP), and α
β
interactions. The carriers showed α-thalassemia phenotype, but one also jaundice and cholelithiasis. Molecular identification of clusters of families in Southern Italy encouraged molecular characterization of mRNA, globin chain analyses, molecular modeling studies, and comparison with globin variants to understand the mechanisms causing the α-thalassemia phenotype. A normal amount of Hb Bernalda/Groene Hart mRNA were found, and molecular modeling highlighted additional H bonds with AHSP. For Hb Southern Italy, showing an unexpected α/β biosynthetic ratio typical of the β-thalassemia type, two different molecular mechanisms were shown: Reduction of the variant mRNA, likely due to the No-Go Decay for the presence of unused triplet ACG at cod 26, and protein instability due to the impairment of AHSP interaction. The UDP glucuronosyltransferase 1A (UGT1A1) genotyping was conclusive in the case of jaundice and cholelithiasis. Multiple approaches are needed to properly identify the mechanisms leading to unstable variants and the effect of a mutation.
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