Onychomadesis in a patient with immunoglobulin class switch recombination deficiency

Area of Science:

• Immunology
• Genetics

Background:

• Hyper IgM syndrome (HIGM) encompasses primary immunodeficiency diseases characterized by defective CD40 signaling in B cells.
• This defect impairs immunoglobulin class switch recombination (CSR) and somatic hypermutation, leading to low IgG and IgA with normal or high IgM.
• Patients with HIGM exhibit increased susceptibility to bacterial infections.

Observation:

• A 3-year-old boy presented with recurrent bacterial infections (skin, respiratory), mucosal ulcers, and diarrhea.
• He developed onychomadesis (nail shedding) during a recent bacterial infection.
• Laboratory results showed high IgM and critically low IgG, IgA, and IgE levels.

Findings:

• Clinical and immunological findings strongly supported a diagnosis of HIGM.
• Molecular analysis excluded mutations in known causative genes (CD40L, CD40, AID, UNG).

Implications:

• This case may represent a novel form of selective CSR deficiency.
• Further research into the genetic basis of this patient's condition is warranted.
• Understanding new forms of HIGM can improve diagnosis and management of primary immunodeficiencies.