**3. Results**

#### *3.1. Demographic Data and Clinical Manifestations*

Thirty-one patients were diagnosed with CVID and treated with immunoglobulin replacement in our hospital center between 2000 and 2021. Four CVID patients (12.9%) suffered from *Giardia* infection during their clinical course. The median age of CVID patients with *Giardia* infection was 44 years old (28–55), two were male (50%) and two were female (50%). The median age at the time of CVID diagnosis was 33 (19–49) years. *Giardia* infection was detected between the first and the fourth year after beginning intravenous immunoglobulin (IVIG) treatment. CVID patients with *Giardia* infection had variable gastrointestinal symptoms and others such as asthenia or febricula. Three of them had *Giardia* reinfections (Cases 1, 2 and 4) and one was a refractory giardiasis (Case 3). In the two females, nodular intestinal lymphoid hyperplasia (NILH) was detected by endoscopy after the first *Giardia* infection, and Case 4 developed a Crohn's disease-*like.* During the evolution of the CVID, without overlapping with the *Giardia* infection, patients also suffered from other clinical conditions, infections and comorbidities, which are summarized in Table 1.

Currently, Cases 1, 2 and 3 are clinically stable. Case 4 continues with gastrointestinal symptoms, arthritis, asthenia, anorexia and intense migraines, numbness in the face and loss of vision, probably associated with her Crohn-like disease. All CVID patients are with IVIG treatment. They receive 0,4 g/kg/day every 21 days except Case 4, which received 0,6 g/kg/day every 21 days because of her clinical condition.
