Sauna test aims to measure sweat loss in rare ROSAH syndrome

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Male or female participants 12 to 65 years of age at screening. * Adolescent participants must be Tanner stage IV or V or have reached an equivalent level of sexual maturity. * For the healthy-volunteer cohort, the participant must be considered healthy based on medical history and investigator assessment. * For the ROSAH syndrome cohort, the participant must have a genetically and clinically confirmed diagnosis of ROSAH syndrome and must be considered clinically stable by the investigator. * Able and willing to complete three controlled sauna heat-exposure tests. * Able to remain seated in a temperature-controlled sauna chamber for up to 30 minutes. * Willing to wear only underwear during testing; female participants may wear a bra. * Willing to have hair at testing sites trimmed or shaved if necessary. * Able to drink 300 mL of water before each test. * Able and willing to comply with study requirements, instructions, and protocol restrictions and likely to complete the study as planned. * Able to provide written informed consent. * For minors, written informed consent must be provided by a parent or legal representative, and written assent must be provided by the participant. Exclusion Criteria: * Baseline body temperature greater than 37.5°C on the day of testing. * Fever, acute infection, or acute illness within 7 days before testing. * History of heat stroke, severe heat intolerance, heat-associated syncope, or severe dehydration. * Clinically significant cardiovascular disease, uncontrolled hypertension, cardiac arrhythmia, or unstable respiratory disease. * Severe anemia or unstable cytopenia, in the investigator's judgment. * Active skin disease, wound, dermatitis, or skin infection at a filter paper placement site. * Pregnant or breastfeeding. * Current use of medication that may substantially affect sweating or thermoregulation unless approved by the investigator, including anticholinergic agents, systemic beta blockers, diuretics, selected antihistamines, or medications that reduce heat tolerance. * Use of depilatory cream, waxing, an epilator, or another chemical or mechanical hair-removal method other than shaving from 7 days before the first sweat test through the final sweat test. * Laser, intense pulsed light, or other energy-based hair removal within 3 months before screening. * Unable to comply with clothing, privacy, or testing requirements. * Any other condition that, in the investigator's judgment, would create an unacceptable risk or interfere with interpretation of the study results.