Free triiodothyronine: \[fT3\]; free thyroxine: \[fT4\]; ATDs: antithyroid drugs

The ESSDAI was designed to measure systemic disease activity in patients with PSjD and consists of 12 domains. The score varies between 0 (no disease activity) and 123 (max disease activity). The clinESSDAI includes all ESSDAI domains except the biological domain.

The Myasthenia Gravis Impairment Index (MGII) is a scoring tool measuring disease severity. It consists of 22 patient-reported outcomes (PRO) and 6 physical examinations (PE). The Ocular PRO score varies between 0 and 18. The higher the score, the more severe the disease.

AE : adverse event ; SAE : serious adverse event ; AESI : adverse event of special interest.

Adverse events, Serious Adverse event and Adverse events of special interest. Adverse events in the 'Infections and infestations' SOC were defined as AESIs because efgartigimod causes a transient reduction in total IgG levels.

ANCOVA Analysis of Percent Change From Baseline in Total IgG Level at Day 29 (ie, 7 days after the fourth IV or SC administration).

A participant was considered a responder for this endpoint (i.e., had a sustained platelet count response) if the participant had platelet counts of ≥50 × 10\^9/L for ≥4 of the 6 analysis visits between Weeks 19 and 24.

Proportion of participants with pemphigus vulgaris who had CRmin within 30 weeks, defined as the absence of new lesions and complete healing of established lesions while the participant was receiving prednisone at ≤10 mg/day for at least 8 weeks.

CASE= Clinical Assessment Scale in Autoimmune Encephalitis; NMDAR=N-methyl-D-aspartate receptor; Neuropsychological Status. The CASE (Clinical Assessment Scale in AIE) includes an assessment of 9 items: seizure, memory dysfunction, psychiatric symptoms, consciousness, language problems, dyskinesia/dystonia, gait instability and ataxia, brainstem dysfunction, weakness. This overall CASE total score ranges from 0 to 27, with a higher score indicating a greater degree of disability.

The Modified Rodnan Skin Score is a scoring tool to assess skin thickness in 17 cutaneous sites across the body. Each site is rated on a semiquantitative score ranging from 0 (normal) to 3 (severe). The total score is the sum of the individual skin scores and can range from 0 to 51.

CRoff = complete remission while receiving efgartigimod PH20 SC or placebo and being off oral corticosteroid therapy for at least 8 weeks. Complete remission is defined as the absence of new lesions, complete healing of existing lesions and absence of pruritus.