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Familial hemophagocytic lymphohistiocytosis (FHL), is a rare autosomal recessive disorder characterized by an impairment of cytotoxic cells and uncontrolled activation of macrophages. This study presents the first description of four patients with FHL type 2 in Latin America. Patient 1 fulfilled the disease diagnostic criteria since 2 months of age, whereas patients 2, 3 and 4 exhibited the typical manifestations of the disease only later in their childhood. The PRF1 genetic analysis in these patients revealed two previously reported mutations: L17fsx50 and R54C. Interestingly, seven out of the 8 alleles evaluated here in patients carried the haplotype R54C/A91V, suggesting that this is a highly frequent FHL type 2 allele in Colombia. This haplotype confers residual cytotoxic function leading to late onset disease. Therefore, this report highlights the remarkable complexity of FHL diagnostic, emphasizing the importance of the genetic characterization of the disease.

Kawasaki disease (KD) is an acute systemic vasculitis of unknown etiology. KD can be complicated with macrophage activation syndrome. The optimal treatment for this KD complication has not been established, and a variety of treatments have been used. Infliximab, a chimeric monoclonal antibody that binds tumor necrosis factor, has proved to be efficacious in IV gammaglobulin resistant KD. We present 2 cases of KD complicated with macrophage activation syndrome, including 1 patient with DiGeorge syndrome successfully treated with a combined treatment of IV gammaglobulin, corticosteroids, cyclosporine, and infliximab.

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