When to Investigate for Secondary Hyperhidrosis: Data from a Retrospective Cohort of All Causes of Recurrent Sweating

Identification of underlying diseases is crucial for secondary hyperhidrosis management, but data are lacking to guide appropriate investigation. To describe aetiologies of recurrent sweating in a hospital setting and the diagnostic performance parameters of their respective clinical/biological features. We performed a monocentric evaluative study in a tertiary care centre. Patients with recurrent generalised sweating were selected the Clinical Data Warehouse (CDW) by screening all electronic hospital documents from the year 2018 using a keyword-based algorithm. All in and out-patients aged ≥ 18 years having reported recurrent sweating for at least 2 weeks in 2018 were included, with a minimum one-year follow-up after symptoms' onset. A total of 420 patients were included. Over 130 different aetiologies were identified; 70 patients (16.7%) remained without diagnosis. Solid organ cancers (14.3% with 13 lung cancers), haematologic malignancies (14.0% with 35 non-Hodgkin's lymphomas) and Infectious Diseases (10.5% including 13 tuberculosis) were the most frequent diagnoses. Other aetiologies were gathered into inflammatory (16.9%) and non-inflammatory (27.6%) conditions. To distinguish non-inflammatory and undiagnosed hyperhidrosis from other causes, fever had a specificity of 94%, impaired general condition a sensitivity of 78%, and C-reactive protein (CRP) > 5.6 mg/l a positive predictive value of 0.86. Symptoms' duration over 1 year was in favour of non-infectious and non-malignant causes (94% specificity). We identified fever, impaired general condition, duration, and CRP as helpful orientation parameters to assess the need for complementary explorations for hyperhidrosis. The study provides a diagnostic algorithm for the investigation of recurrent sweating.KEY MESSAGESIn a hospital setting, malignancies and infections are the most frequently associated diseases, but 1/5 remain without diagnosis.Fever is a specific but not sensitive sign to distinguish inflammatory conditions.Over 1 year duration of symptoms significantly reduce the probability of malignancy or infection as the underlying diagnosis.