Background: Acquired idiopathic generalized anhidrosis (AIGA) represents a heterogeneous clinical syndrome including sudomotor neuropathy and failure of the sweat glands. However, most AIGA cases comprise idiopathic pure sudomotor failure (IPSF), a distinct subgroup without sudomotor neuropathy or sweat gland failure.
Methods: Eight patients with IPSF (mean +/- SD age 20 +/- 5 years) were assessed by thermoregulatory and pilocarpine-induced sweating tests, as well as emotional sweating using sudorometer (4 cases), microneurography of skin sympathetic nerve activity (2 cases), and skin biopsies from the forearm or axilla (3 cases).
Results: Clinical features of IPSF comprise early onset; acute or sudden onset; concomitant sharp pain or cholinergic urticaria over the entire body; lack of autonomic dysfunction other than generalized anhidrosis; elevated serum IgE levels; and marked response to steroid. Sudomotor function testing revealed complete absence of thermoregulatory sweating, but well-preserved emotional sweating; pilocarpine did not induce sweating, and microneurography revealed that bursts of skin sympathetic nerve activity were not decreased; and skin biopsy displayed no morphologic abnormalities in sweat glands. The first two findings suggest lesions on the postsynaptic side of the nerve-sweat gland junction.
Conclusion: The lesions in IPSF may be in the muscarinic cholinergic receptors of sweat glands. Allergic mechanisms are probably involved in its pathophysiology.