title: Chronic gingivitis in a new BTK mutation.
abstract: A 5-yr-old Caucasian boy with a new mutation in Bruton's tyrosine kinase (BTK) is described. Full sequencing of the BTK gene revealed a point mutation in exon 17 resulting in an amino acid change from tryptophan to serine at location 581 of the tyrosine kinase domain. Clinically the child presented with chronic gingivitis and had no prior history of bacterial infections. Whereas serum immunoglobulin M (IgM) levels were undetectable, IgG levels were in the low normal range. The gingivitis completely resolved after intravenous immunoglobulin therapy. Lymphocyte phenotyping revealed 0.05% B cells in his peripheral blood, which were IgG(-), IgM(+), IgD(+), CD38(+), CD20(+), CD27(-). However, 40% of the B cells also expressed CD5. This subpopulation of B cells has not previously been described in X-linked agammaglobulinaemia (XLA) patients. We suggest that the occurrence of CD5(+) B cells could correlate with a late onset and mild clinical presentations of XLA.
authors.affiliation: Department of Paediatrics, Nepean Hospital, Western Clinical School, University of Sydney, Sydney, NSW, Australia.
authors.forename: Anthony J W
authors.initials: AJ
authors.lastname: Liu
authors.forename: Lan-Phuong
authors.initials: LP
authors.lastname: Dao-Ung
authors.forename: David
authors.initials: D
authors.lastname: McDonald
authors.forename: Ralph
authors.initials: R
authors.lastname: Nanan
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D002675:Child, Preschool; D002908:Chronic Disease; D005434:Flow Cytometry; D005891:Gingivitis / Q000235:genetics*; D006801:Humans; D007136:Immunoglobulins / Q000097:blood; D016130:Immunophenotyping; D008297:Male; D017354:Point Mutation; D011505:Protein-Tyrosine Kinases / Q000097:blood / Q000235:genetics* / Q000276:immunology
chemical_list: D007136:Immunoglobulins; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human