*Article* **Incidence, Management Experience and Characteristics of Patients with Giardiasis and Common Variable Immunodeficiency**

**Irene Díaz-Alberola 1,2,3,\*, Juan Francisco Gutiérrez-Bautista 3, Andrea Espuch-Oliver 4, José María García-Aznar 5, Per Anderson 3,6, Pilar Jiménez 1,3, Carmen Hidalgo-Tenorio 3,7,† and Miguel Ángel López-Nevot 1,3,6,†**


**Abstract:** Common variable immunodeficiency (CVID) is an antibody immunodeficiency with a wide variety of clinical and immunological manifestations, and whose genetic cause is found in about 25% of diagnosed cases. *Giardia lamblia* is one of the main causes of gastrointestinal infections in CVID. 5-Nitroimidazoles are the most used first-line treatment, but nitroimidazole-refractory giardiasis is increasing. Nevertheless, only a few cases of refractory giardiasis in CVID have been reported. This study aimed to determine the incidence of *Giardia* infection in our CVID cohort, shows our management experience and describes patients' phenotypic features. Clinical data collection, immunological, immunogenetics and microbiology assays were performed, and previous cases of giardiasis in CVID were reviewed. The incidence of symptomatic giardiasis was 12.9%. The main immunological features were undetectable or decreased IgA levels and reduced switched memory B cells. A probable *PTEN* pathogenic variant was detected in one. Three patients responded to metronidazole but suffered reinfections, and one was a refractory giardiasis eradicated with innovative quinacrine plus paromomycin combination. This work could contribute to the decisionmaking and therapeutic management of future patients with CVID and giardiasis, highlighting the importance of the early detection and treatment of infections in patients with CVID to ensure a good quality of life.

**Keywords:** CVID; immunodeficiency; gastrointestinal infections; *Giardia*; giardiasis; refractory; treatment; immunology; immunogenetic
