Introduction:

Hyper-IgM syndrome is an innate error of immunity in which there is a defect in change of isotype of immunoglobulins, with decreased values of IgG, IgA, and IgE, but normal or increased level of IgM. This predis- poses to infectious processes at the respiratory and gastrointestinal levels, as well as autoimmune diseases and neoplasm.

Case report:

A 5 year 7-month-old boy with a history of 2 pneumonias, one of them severe, and chronic diarrhea since he was 2 years old. Persistent moderate neutropenia decreased IgG and elevated IgM. Cytometry flow con- firmed absence of CD40L. Clinical evolution with early hepatic involvement.

Discussion:

Hyper-IgM syndrome predisposes to liver damage, so a complete evaluation is required as well as early diagnosis. Active anti-infective treatment and control of the inflammatory response are key to the treatment of liver damage.