Key Inclusion Criteria:  Adult patients, 18 years or older (16 years or older in the UK) Diagnosed with Pachyonychia Congenita (PC), genetically confirmed  Key Exclusion Criteria:  Any history of allergy or hypersensitivity to sirolimus, or sirolimus-like medications. Any significant concurrent condition (including conditions involving or inferior to the ankle) that could adversely affect the patient's participation and/or the assessment of the safety and efficacy in the study. Participation in any other interventional clinical research trial within 30 days prior to the screening visit or during the patient's participation in this study