Leukocyte adhesion deficiency-I caused by a novel mutation in ITGB2 presenting with pyoderma gangrenosum

DNA collected from blood was submitted to Fulgent Diagnostics for sequencing. DNA was barcoded and enriched for the coding exons of targeted genes using hybrid capture technology. Prepared DNA libraries were sequenced using Next Generation Sequencing technology. Following alignment, variants were detected and interpreted manually using locus specific databases, literature searches and other molecular biological principles. All variants were confirmed by Sanger sequencing. Patient consent was obtained and recorded through the Canadian Primary Immunodeficiency Evaluation Study (C-PRIMES).

Flow cytometric immunophenotyping of peripheral blood was performed by Mayo Medical Laboratories to evaluate the presence of the CD11/CD18 complex using monoclonal antibodies directed against the CD11 isoforms, CD11a and CD11b, and CD18 antigens.

A female patient born to non-consanguineous Caucasian parents presented at age 7 years old with multiple painful, erythematous and necrotic papules on the inner thigh and intermittent fevers. She was admitted for intravenous antibiotics following a failed course of oral cephalexin. Wound and blood cultures were negative. She had a significant lymphocytosis, 35.1 × 10⁹/L, with predominate neutrophils, 28.4 × 10⁹/L. Past infectious history included 1 previous cutaneous infection following an abrasion and molluscum contagiosum. She did not have delayed separation of the umbilical cord. Partial evaluation of the immune system was performed at age 7 years old and reported normal lymphocyte subsets (CD20⁺, CD3⁺, CD3⁺/CD4⁺, CD3⁺/CD8⁺, and CD3⁻/CD56⁺CD16⁺), normal immunoglobulin levels, normal vaccine titers, and normal neutrophil oxidative burst index. The patient had a persistent leukocytosis ranging from 38.8–10.8 × 10⁹/L and neutrophilia ranging from 32.6–11.3 × 10⁹/L.

Fifteen months later, she presented to the emergency room with papules that rapidly progressed to necrotic ulcerations on the thighs and fever requiring another admission for intravenous antibiotics (Figures 1–4). Dermatology was consulted and a skin biopsy was performed. The skin biopsy reported epidermal necrosis with superficial dermal abscess with neutrophils and eosinophils consistent with superficial granulomatous pyoderma. Evaluations for inflammatory bowel disease, including colonoscopy with biopsies, and rheumatologic disorders were negative and the patient was treated for presumed idiopathic PG with oral prednisone and cyclosporine. Genetics was consulted due to the persistent nature and difficult to treat skin lesions. A literature review led to the article by Madkaikar et al, describing patients with PG in the setting of persistent neutrophilia who were diagnosed with LAD-1. Given this, at age 9 years and 6 months, molecular genetic testing was arranged and a homozygous frameshift mutation was identified in the ITGB2 gene (c.2070del, p. Asp690Glufs*25) located on 21q22.3. This was predicted to result in premature truncation of the protein and according to the American College of Medical Genetics (ACMG) guidelines the variant was classified as pathogenic. A heterozygous variant in NOD2 (c.3019dup, p.Leu1007Profs*2) was also identified and was classified as a susceptibility factor for Crohn’s disease. Flow cytometry reported absent expression of CD18 on lymphocytes with significantly reduced expression on granulocytes. There was normal expression of CD11a on lymphocytes and monocytes and absent expression on granulocytes. CD11b was absent on lymphocytes, significantly reduced in monocytes, and close to normal on granulocytes. The patient was diagnosed with LAD-I. Immunosuppressive medications were discontinued and she was started on prophylactic antibiotics. The PG has resolved since starting prophylactic antibiotics with amoxicillin. She has had intermittent skin lesions that resolve with a course of oral antibiotics.

Patient 2, the brother of patient 1, presented at age 13 years with small painful papules on the lateral aspect of upper thigh. Past infectious history was remarkable for molluscum contagiosum. He did not have delayed separation of the umbilical cord. Based on the sibling’s diagnosis of LAD-I, molecular genetic testing was completed and he was confirmed to have the same homozygous mutation in ITGB2 (c.2070del, p.Asp690Glufs*25). The parents of patient 1 and patient 2 also had molecular genetics testing completed and were both found to be carriers of the mutation in ITGB2. The patient was diagnosed with LAD-I and was started on prophylactic antibiotics to prevent the development of cutaneous infections. The papules have resolved since starting prophylactic antibiotics.