Theo Gulen

Theo Gulen

Affiliated to Research
Visiting address: BioClinicum, J7:30, Akademiska stråket 1, 17164 Stockholm
Postal address: K2 Medicin, Solna, K2 Imm o alle Nilsson G, 171 77 Stockholm

About me

  • I am an Associate Professor of Allergy and affiliated to Karolinska Institutet. In addition, I am a board certified physician in the fields of Internal Medicine, Clinical Immunology and Allergology and currently serve as a Senior Consultant in the Respiratory Diseases and Allergy Clinic, Karolinska University Hospital, Huddinge. In 2014, I earned my PhD from the Karolinska Institutet on a project focusing on the intriguing association of Mastocytosis and Anaphylactic reactions.


  • *Allergy, Anaphylaxis and Mastocytosis: Disorders Manifesting with Mast Cell Activation*

    My ongoing research aims to gain a comprehensive understanding of the mechanisms causing systemic mast cell activation and associated symptoms. This will be achieved by exploring distinct clinical and biological features observed in patients with “Mast Cell Activation Disorders”, such as patients with severe anaphylaxis, mast cell activation syndrome (MCAS), and mastocytosis. Furthermore, my research also focuses on identifying biomarkers of mast cell hyperreactivity and endotypes. The objective is to elucidate the mechanisms causing inherent increase in reactivity and releasability of mast cells, which serves as the primary perturbation leading to severe and uncontrolled mast cell activation in these patients.

    Anaphylaxis is a rapidly developing and serious hypersensitivity reaction that can concurrently affect multiple organ systems. It remains as a clinical entity and the diagnosis is based on constellation of different signs and symptoms according to the World Allergy Organization (WAO) diagnostic criteria, which involves two or more organs including skin/mucosal membranes, airways, cardiovascular, and/or gastrointestinal systems. These criteria enabled clinicians across the world to 'speak the same language' and facilitated tremendously patients and acute care physician to recognize and treat it promptly. It also made possible for scientist to report meaningful, comparable data. However, despite significant progresses in allergology and immunology during the last 2-3 decades, understanding of anaphylaxis for an allergist is fairly limited at present with respect to factors determining severity, underlying intracellular effector mechanisms within mast cells, co-factor influence, and immune mechanisms involving in mast cell activation syndromes (MCAS) and disorders (MCAD).

    To investigate this, future studies should approach anaphylaxis in a concerted manner with detailed phenotyping/endotyping by exploring the role of mast cell activation biomarkers in plasma and urine. In this context, patients with MCAD, such as mastocytosis are of great relevance to study patients with severe anaphylaxis, as these patients usually develop recurrent, severe anaphylaxis. Therefore, the main focus of the current project will be exploring clinical and biological features of MCAD patients to better understand mechanisms of anaphylaxis by screening specific diagnostic and prognostic biomarkers in patients with mastocytosis. We also aim to identify novel biomarkers of severe anaphylaxis.

    Ultimately, understanding these regulatory mechanisms might help to predict patients with severe anaphylaxis as well as to develop personalized treatment options for individual patients with mastocytosis and other mast cell disorders, such as severe allergies.



  • I have been actively involving in teaching activities in the medical education at KI for the graduate, post-graduate students as well as professional levels.
    My teaching duties are focused on allergic disorders including anaphylaxis, mast cell disorders, asthma, and mechanisms leading to allergies at the graduate level for third-year medical students in form of cathedral lectures, practical applications in form of PBL and direct clinical tutorship at the departments of Medicine Solna and Huddinge, Karolinska Institutet.
    I am Director of post-graduate training for Allergy Residents/Fellows in Karolinska University Hospital. This task requires planning and ascertaining of quality in training of allergy residents
    Teaching about Allergic diseases in broad for residents/specialist of Internal Medicine, Allergy and Pneumatology as well as general practitioners and doctoral students.

    *PhD supervisor*
    Principal supervisor for Ilia Brooke.

    Jennine Grootens, PhD 2019, KI, Co-supervisor

Selected publications


All other publications


  • Affiliated to Research, Department of Medicine, Huddinge, Karolinska Institutet, 2024-2027
  • Affiliated to Research, Department of Medicine, Karolinska Institutet, 2023-2026

Degrees and Education

  • Degree Of Doctor Of Philosophy, Department of Medicine, Huddinge, Karolinska Institutet, 2014

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