Case report: Chronic gingivitis in a new BTK mutation

• Published in: European journal of haematology 2006-02, Vol.76 (2), p.171-175
• Main Authors: Liu, Anthony JW, Dao-Ung, Lan-Phuong, McDonald, David, Nanan, Ralph
• Format: Article
• Language: English
• ISSN: 0902-4441; 1600-0609
• DOI: 10.1111/j.0902-4441.2005.00571.x

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 super(-), IgM super(+), IgD super(+), CD38 super(+), CD20 super(+), CD27 super(-). 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 super(+) B cells could correlate with a late onset and mild clinical presentations of XLA.