Clinical Research Directory

Inclusion Criteria: * Has received at least 1 dose of Gamifant 0-7 days prior to ICF date or is prescribed to initiate Gamifant. * Aged ≤80 years at index Gamifant administration. * Diagnosis of secondary HLH/MAS according to the treating physician. * Diagnosis or suspicion of Still's disease (sJIA or AOSD) according to the treating physician. * Patients who have shown inadequate response or intolerance to high-dose glucocorticoids or who have recurrent MAS, according to the treating physician. Recurrent MAS is defined as any MAS episode that has occurred after resolution of the first-ever MAS episode. * Patient agrees to provide relevant specimen (blood, sputum, and/or urine samples) for laboratory testing as outlined in the study protocol. * Informed consent must be obtained from the patient or the patient's legally authorized representative. * For minors capable of providing assent (as determined by local regulations and the Investigator's judgment), informed assent must be obtained in accordance with applicable local regulations. If a minor is unable to provide assent due to age, developmental stage, or medical condition, the reason will be documented. Exclusion Criteria: * Diagnosis of pHLH or sHLH consequent to proven metabolic, malignancy, or a rheumatic disease other than Still's disease at index date. * Clinically active Mycobacterium tuberculosis (typical and atypical), Histoplasma capsulatum, or Salmonella infections at the index date based on investigator's assessment. * Evidence of leishmania infections at the index date based on investigator's assessment. * Concurrent participation in an interventional clinical trial. * Severe, uncontrolled concurrent illness at the index date likely to confound outcome assessment with expected survival \<28 days based on investigator's assessment. * Pregnant at the time of study entry