Variable CD18 expression in a 22‐year‐old female with leukocyte adhesion deficiency I: Clinical case and literature review

KEY CLINICAL MESSAGE: Partial leukocyte adhesion deficiency type 1 (LAD‐1) deficiency is extremely rare condition with milder infectious manifestation and immune system imbalance leads to increased risks of autoinflammatory complications, such as pyoderma gangrenosum, that can be triggered by trauma or pregnancy. In patients with spice‐site ITGB2 variants, partial expression can occur due to different β2 integrin isophorms expression. ABSTRACT: LAD‐1, OMIM ID #116920 is a rare, autosomal recessive disorder that results from mutations in the ITGB2 gene that encodes the CD18 β2 integrin subunit. According to the CD18 expression, LAD‐1 is categorized as severe (<2%), moderate (2%–30%), or mild (>30%). Here, we describe a 22‐year‐old female, who presented with inflammatory skin disease and oral cavity, as well as respiratory tract infections during the first year of life. LAD‐1 was diagnosed at the age of 2 years by low expression of CD18 (1%). Whole‐exome sequencing identified homozygous c. 59‐10C>A variant in the ITGB2 gene. Despite severe phenotype, the patient survived to adulthood without hematopoietic stem cell transplantation and became pregnant at the age of 20 years, with pregnancy complicated by a pyoderma gangrenosum‐like lesion. During her life, CD18 expression increased from 1% to 9%; at 22 years of age, 5% of neutrophils and 9% of lymphocytes were CD18(+). All CD18(+)‐lymphocytes were predominantly memory/effector cytotoxic T cells. However, revertant mosaicism was not being established suggesting that CD18 expression variability may be mediated by other mechanisms such as different β2 integrin isophorms expression.