The goal of this non-interventional study (NIS) is to collect real-world data to describe the natural history of Netherton Syndrome (NS).

Inclusion criteria [for Part 1 and Part 2]

1. Confirmed diagnosis of NS by at least one of the following:

   • Genetic testing of mutations in Serine Protease Inhibitor of Kazal Type 5 (SPINK5);
   • Absence or major deficiency of the protein Lympho-Epithelial Kazal-Type-Related Inhibitor (LEKTI) in skin biopsy;
   • Clinical assessment (signs and symptoms).

2. Provision of consent or assent (i.e., by parent or legal guardian) as required by local regulations:

   • [Part 1] to authorise access to existing medical records for study data collection;
   • [Part 2] to participate in the longitudinal 52-week evaluation of disease severity and clinical outcome assessments.

   [for Part 2 only]

3. Not participating in a clinical trial at the time of study enrolment for Part 2.

Exclusion criteria [for Part 1 and Part 2]

1. Patient who has died prior to 2002.
2. Patient whose last known survival status is dated prior to 2002 (i.e., patient has been lost to clinical follow-up since 2002).

Sites will identify all patients diagnosed and treated for NS in routine clinical practice to form the base cohort for study eligibility assessment. Patients in the base cohort will be further reviewed for study eligibility based on the criteria below.

Part 1 - retrospective data collection:

In Part 1 of the study clinical data will be abstracted from patients' existing medical records from the date of study enrolment back to the date of initial diagnosis of NS.

Part 2 - prospective data collection:

In Part 2, patients who are not enrolled in a clinical trial at the time of study inclusion will be asked to provide additional consent/assent to participate in a 52-week follow-up for continuous clinical data collection from medical records and completion of Clinician-Reported Outcomes (ClinRO) and Patient-Reported Outcomes (PRO) assessments.

Clinical studies sponsored by Boehringer Ingelheim, phases I to IV, interventional and non-interventional, are in scope for sharing of the raw clinical study data and clinical study documents. Exceptions might apply, e.g. studies in products where Boehringer Ingelheim is not the license holder; studies regarding pharmaceutical formulations and associated analytical methods, and studies pertinent to pharmacokinetics using human biomaterials; studies conducted in a single center or targeting rare diseases (in case of low number of patients and therefore limitations with anonymization).

For more details refer to: https://www.mystudywindow.com/msw/datatransparency

The overall study population included all identified participants who were diagnosed and treated for NS in routine clinical practice, regardless of whether data was previously existing or newly collected.

Adverse event information was not applicable for this study.

This was a natural history study of a disease with no objective to evaluate exposure to any specific treatment. Thus, no adverse events were collected on an individual case level as no safety reporting was applicable for the study.

Study was terminated early by the sponsor. No outcome measures data were collected.