PMC9218906_01
PMC9218906_02
Patient at 21 months old showing self-mutilation injury to tongue (A) and fingers (B). Histamine challenge testing of the patient revealed central area of pallor (1.5 cm2) but a complete absence of surrounding erythema (C) confirming functional absence of small autonomic fiber function. Normal control (D) shows an area of erythema extending several centimeters beyond the central area of pallor.
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PMC9218906_02_10.1177_2329048X221108826-fig1.jpg
fig1-2329048X221108826
Subsequently, she had bit a portion of her tongue and had multiple bites on her fingers and hands with deep bites to the region of her first dorsal interosseus bilaterally at various stages of healing (Figure 1A and B). The histamine challenge test protocol involves the intradermal administration of histamine phosphate 0.1 mL (0.275 mg/mL) instilled in her ventral forearm She demonstrated no response to the administration of histamine phosphate, specifically a central area of pallor or wheal at the site of injection with no surrounding erythema (Figure 1C). For comparison a control subject shows a normal response as indicated be the sizeable area of erythema (Figure 1D).