IgM Deficiency Associated With Connexin Mutation in an 18-Year-old Male

Abstract

IgM deficiency is characterized by remarkably low serum levels of IgM with normal IgG and IgA levels. These patients clinically present with recurrent infections, autoimmune disorders, and malignancies. While unknown, the proposed mechanisms explain the pathophysiology as an issue due to impaired IgG antibody response. The connexin genes encode for gap junctional proteins where mutations can cause hearing deficits and immune dysregulation. We present a unique case of an 18-year-old patient with recurrent sinusitis, diagnosed connexin-26 mutation and an IgM deficiency. An 18-year-old male with chronic sinusitis, Marfanoid joint hypermobility syndrome, and sensorineural hearing loss due to connexin-26 deficiency with bilateral cochlear implants. This patient's mutation is a GJB2 deletion located on chromosome 13 which encodes for the connexin-26 protein. The patient experienced recurrent infections, and serum immunoglobulins showed a normal IgA (84 mg/dL; normal: 70-400 mg/dL), IgG (922 mg/dL; normal: 700–1600 mg/dL) and reduced IgM (26 mg/dL; normal: 40–230 mg/dL) levels. The patient was responsive to Mumps, Measles, Rubella, and Diphtheria vaccinations among others, consistent with SIGMD diagnoses. Antibody responses to polysaccharide antigens were absent. The leukocyte counts were within normal limits. His parents are connexin-26 deficient carriers, and his older brother was diagnosed with SIGMD. Connexin-26 has been identified with multiple immunological mechanisms. Although mutations of this gene have no direct tie to antibody formation in relation to IgM, the presence of these 2 pathologies in 1 patient is intriguing and may suggest a pathophysiologic connection. We describe the first case of connexin mutation with an IgM deficiency in an 18-year-old male.