Prospective Psychometric Evaluation Study of a Patient-reported Outcomes (PRO) Instrument for Congenital Thrombotic Thrombocytopenic Purpura (cTTP, Upshaw-Schulman Syndrome [USS], Hereditary Thrombotic Thrombocytopenic Purpura [hTTP]

Inclusion criteria:

1. The participant is an adolescent aged 12 to 17 years or an adult aged ≥18 years;

2. The participant has been diagnosed with congenital thrombotic thrombocytopenic purpura
(cTTP) and is currently receiving prophylactic or on-demand treatment with fresh
frozen plasma (FFP), or solvent detergent (S/D) plasma, or Von Willebrand
Factor/Factor VIII (VWF/FVIII) concentrates;

3. In the instance that the participant is identified and recruited remotely
(Direct-to-Patient (DtP) recruitment), access to the internet and possession of an
internet-connecting device is required;

4. The participant has provided informed consent, and in the instance that the
participant is an adolescent, a legal guardian has provided informed consent and the
adolescent has provided assent.

Exclusion criteria:

1. The participant cannot read nor write;

2. The participant is non-English speaking;

3. The participant is currently participating in a clinical trial.