Bruton's tyrosine kinase (BTK), encoded by the BTK gene, is a cytoplasmic protein critical in B cell development. Mutations in the BTK gene cause X-linked agammaglobulinemia (XLA), a primary immunodeficiency with characteristically low or absent B cells and antibodies. This report describes a five year-old boy who presented with otitis externa, arthritis, reduced immunoglobulins and no B cells. Flow cytometry showed undetectable monocyte BTK expression. Sequencing revealed a novel mutation at exon 13 of the BTK gene which created a de novo splice site with a proximal 5 nucleotide loss resulting in a truncated BTK protein. The patient still suffered from ear infection despite intravenous immunoglobulin replacement therapy. In this study, mosaicism was seen only in the mother's genomic DNA. These results suggest that a combination of flow cytometry and BTK gene analysis is important for XLA diagnosis and carrier screening.
Fungal osteomyelitis is a rare opportunistic infection. It exhibits some clinical and radiological similarities to several other bone pathologies. A diagnostic delay may result in significant increase in morbidity. We report a case of a 37-year-old man with underlying hypogammaglobulinaemia presented with isolated cryptococcal osteomyelitis of the femur.
We describe here a case of cryptococcal empyema thoracis and periauricular pyogenic abscess in a child with Bruton's agammaglobulinaemia. The cryptococcal empyema thoracis was treated with intravenous amphotericin B and intravenous fluconazole for six weeks followed by oral fluconazole. The pyogenic periauricular abscess was surgically drained and treated with intravenous ceftazidime and cloxacillin for two weeks. He also received monthly intravenous immunoglobulin.