Development of hemophagocytic lymphohistiocytosis in triplets infected with HHV-8

Abstract

Hemophagocytic lymphohistiocytosis (HLH) is a rare disorder of immune dysregulation, characterized by end-organ damage from lymphocytic infiltration and macrophage activation. All known mutations associated with the HLH occur in genes critical in the perforin-granzyme pathway. Herein, we report HLH occurring in 2 female triplet infants who also had associated human herpesvirus type 8 (HHV-8) infections. The subjects had identical novel compound-heterozygous mutations in the Perforin alleles, resulting in undetectable perforin expression and NK-cell cytotoxicity. Both infants also had evidence of infection with HHV-8. These reports are, to our knowledge, the first cases of HLH in triplets and the first reported cases of HHV-8 infection associated with HLH in non-renal transplant and non-HIV-infected subjects.

Figure 1.

Hemophagocytosis and lack of perforin detection and NK-cell cytotoxicity in case reports A and B. (A) Bone marrow evaluation of triplet A (case report A; i-iii) and triplet B (case report B; iv-vi), showing hemophagocytosis of bone marrow elements (eg, red blood cells and neutrophils) by histiocytes. All pictures are from May-Grünwald/Giemsa–stained slides and are shown at × 400 magnification. (B) Perforin and granzymes A and B antibody reactivity in CD56⁺CD8^– NK cells from control (top row), triplet A (middle row), and triplet B (bottom row). Percentage of positive cells is shown in each quadrant. GzmA indicates granzyme A; GzmB, granzyme B. (C) Representative flow-based cytotoxicity results, demonstrating NK-cell–induced apoptosis (FSC^lo/7-AAD^+hi) of major histocompatibility complex (MHC) class I–negative target cells (K562) in control, triplet A, and triplet B. Percentage of apoptotic target cells is shown in the R3 gate of each panel. FSC indicates forward scatter; 7-AAD, 7-aminoactinomycin D. (D) Summary of NK-cell killing, demonstrating the average percentage of apoptotic target cells detected in the R3 gate for each subject. Effector-target (E / T) ratio was 50:1 for all samples. Values shown are the mean ± SD. **P < .01, NS = not significant.

Figure 2.

PCR analysis of buffy coat and CSF samples from affected triplets for HHV-8. Specific PCR product for ORF-26 of HHV-8 is shown (336-bp product; arrow). Lane 1, triplet B CSF sample; lane 2, triplet A buffy coat sample; lane 3, Mewo cell line (negative control); lane 4, BC-3 cell line (positive control); lane 5: DNA bp ladder.