Carriers of Recessive WNK1/HSN2 Mutations for Hereditary Sensory and Autonomic Neuropathy Type 2 (HSAN2) Are More Sensitive to Thermal Stimuli

Hereditary sensory and autonomic neuropathy type 2 (HSAN2) is a rare recessive genetic disorder characterized by severe sensory loss affecting the tactile, thermal and nociceptive modalities. Although heterozygous carriers of nonsense mutations in the HSN2 gene, called with-no-lysine(K)-1 (WNK1), do not develop the disease, historical and experimental evidence suggests that these individuals might perceive somatosensory stimuli differently from others. Using the method-of-limits, we assessed the thresholds for warmth detection, cool detection, heat pain and cold pain in 25 mutation carriers and 35 controls. In group analyses, carriers displayed significantly lower warmth (p < 0.001) and cool (p < 0.05) difference thresholds, and also tended to report cold pain at higher temperatures (p < 0.095), than controls. Similarly, matched-pair analyses showed that carriers are significantly more sensitive to warm stimuli (p < 0.01) and cold pain stimuli (p < 0.05), and tend to be more sensitive to cool stimuli (p < 0.11). Furthermore, the differences between the warmth detection thresholds of the carriers and those of gender- and sex-matched wild types significantly increased with age (r = 0.76, p = 0.02), and in carriers cool detection thresholds did not increase with age (r = 0.27, p = 0.24) as expected and observed in controls (r = 0.34, p = 0.05). This study demonstrates that the carriers of a recessive mutation for HSAN2 display greater sensitivity to innocuous thermal stimuli, as well as for cold pain, suggesting a possible environmental adaptive advantage of the heterozygous state.