• Signed informed consent form

• Age \>= 18 and \<=75 at the time of signing informed consent form (except for BP; Age \>=18 and \<= 85 with Karnofsky score \>= 60% at screening)

• Ability to comply with the study protocol

• For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use highly effective contraceptive methods

• For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive measures, and agreement to refrain from donating sperm

• APS cohort: Established primary APS defined by the following criteria (at least one of the laboratory criteria and one of the clinical criteria must be met):

‣ Laboratory criteria (aPL profile)

• Persistently positive lupus anticoagulant (LA) test

∙ Persistently positive anticardiolipin (aCL) immunoglobulin G (IgG) isotype

∙ Persistently positive anti-beta-2 glycoprotein-1 (aβ2GPI) IgG isotype

⁃ Clinical criteria

• Livedoid vasculopathy and presence of skin ulcer

∙ Acute/chronic aPL nephropathy

• BP cohort:

‣ 1\) Age \>= 18 and \<= 85 with Karnofsky score \>= 60 %

⁃ 2\) Predominant cutaneous lesions

⁃ 3\) Diagnosis with BP with following assessments positive:

⁃ a Positive direct immunofluorescence, and either

⁃ b Positive indirect immunofluorescence, or

⁃ c Positive serology on ELISA for BP180 autoantibody

⁃ 4\) Bullous Pemphigoid Disease Area Index (BPDAI) score \>= 20

⁃ 5\) Weekly average of daily Peak Pruritus Numerical Rating Score (PP-NRS) \>=4

⁃ 6\) Accept to take photograph of bullous lesions

• BS cohort:

‣ 1\) Diagnosed with BS

⁃ 2\) Oral ulcers that occurred at least 3 times in the previous 12 month period

⁃ 3\) Have at least 2 oral ulcers over the 4 weeks prior to screening

⁃ 4\) Have at least 2 oral ulcers at Week 0

⁃ 5\) Have prior treatment with at least 1 non-biologic BS therapy

⁃ 6\) Patients who need systemic therapy as whose oral or mucocutaneous ulcers cannot be adequately controlled by topical therapy

• DM cohort:

‣ 1\) Diagnosed with definite or probable inflammatory myopathies and categorized as DM

⁃ 2\) Patients with inadequate response to corticosteroids and/or immune-suppressants or intolerance to DM therapies

⁃ 3\) Manual Muscle Test-8 (MMT-8) score \< 142, with at least one abnormality in the following Core Set Measures:

• Patient Global Activity Visual Analogue Scale (PtGA-VAS) \>= 2 cm

∙ Physician Global Activity Visual Analogue Scale (PhGA-VAS) \>= 2 cm

∙ Global extra-muscular activity \>= 2 cm

∙ At least one muscle enzyme \> 1.5 times upper limit of normal (ULN)

∙ Health Assessment Questionnaire (HAQ) \>= 0.25

⁃ 4\) Moderate to severe DM defined as CDASI activity score \> 14

⁃ IMNM cohort:

∙ 1\) Clinically Diagnosed with IMNM as anti-HMGCR myopathy or anti-SRP myopathy

‣ 2\) Creatine kinase (CK) \> 1,000 U/L

‣ 3\) Patients who have an inadequate response to corticosteroids and/or immunosuppressants or intolerance to IMNM therapies

‣ 4\) MMT-8 score \< 142

⁃ ITP cohort:

∙ 1\) Confirmed diagnosis of persistent/chronic ITP based on the following criteria:

⁃ ITP defined per the current guidelines

• Platelet count \<= 30 × 10\^9/L on 2 consecutive occasions

‣ 2\) Lack of an sustained adequate platelet count response to a thrombopoietin receptor agonist and at least one other ITP treatment or a second thrombopoietin receptor agonist (TPO-RA)

‣ 3\) A history of response with an platelet counts increase more than 20 × 10\^9/L from baseline by at least one prior line of therapy