Anhidrosis accompanied by cholinergic urticaria‐like rash and dermal pain in a patient with Sjögren's syndrome

Cholinergic urticaria (CholU)-like rash and dermal pain on sweating occur in patients with acquired idiopathic generalized anhidrosis (AIGA). However, it is unclear whether these are symptoms specific to AIGA among the various types of acquired generalized anhidrosis/hypohidrosis (AGAH). Moreover, the pathogenesis underlying CholU-like rash and dermal pain observed with anhidrosis remains to be clarified. A 20-year-old Japanese man with Sjögren's syndrome (SS) presented with anhidrosis. Transient stinging pain on the skin and pinpoint wheals were observed when his body temperature increased. Thermoregulatory sweat testing revealed anhidrotic areas covering 69% of the body surface area with a symmetrical distribution. A high concentration of histamine was detected (506 ng/mL) in the sweat. A skin biopsy specimen from the anhidrotic area showed the inflamed secretory portion of eccrine glands. This suggested inflammation-mediated damage to sweat glands, consistent with AGAH related to SS. Furthermore, immunohistochemical analysis revealed an ectopic distribution of dermcidin, a sweat-specific peptide, in the dermal tissue surrounding the secretory portion of eccrine glands. The expression of claudin-3, a tight junction (TJ) component of sweat glands, decreased or distributed in a mottled manner in the secretory portion. No decreased expression of muscarinic cholinergic receptor M3 was detected. These results suggested that sweat had leaked into the dermis in association with impaired TJ in the secretory portion, along with the damage to inflamed sweat glands related to SS. Collectively, CholU-like rash and dermal pain on sweating were observed in an AGAH patient with SS. The sweat leakage into the dermis may contribute to the development of the rash and pain.