ID: 62: HEMOPHAGOCYTIC LYMPHOHISTIOCYTOSIS CAUSED BY INFECTION BY EHRLICHIA CHAFFEENSIS: A CASE REPORT

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of pathologic immune activation which occurs as either a familial disorder or sporadic condition. The diagnosis of HLH requires a presence of five out of eight criteria: fever, splenomegaly, pancytopenia, hypertriglyceridemia and/or hypofibrogenemia, hemophagocytosis in bone marrow, spleen or lymph nodes, low or absent natural killer cell activity, hyperferritinemia, and high level of soluble interleukin-2 receptor. We present a case of HLH triggered by severe infection with Ehrlichia chaffeensis in a patient taking methotrexate for seronegative spondyloarthropathy.

A 45-year-old man with a history of ankylosing spondylitis taking methotrexate presented to a community hospital with acute onset of nausea, vomiting and diarrhea. Physical examination revealed a febrile patient with diffuse abdominal tenderness with splenomegaly and diffuse maculopapular rash involving the trunk and all extremities. Labs showed leukopenia and thrombocytopenia. Clinical course was complicated by development of acute renal failure, altered mental status and hypoxic respiratory failure requiring endotracheal intubation and mechanical ventilation. Plasmapheresis was initiated due to concern for thrombotic thrombocytopenic purpura with no response. A bone marrow biopsy was performed which revealed a tri-lineage hematopoiesis with increased number of histiocytes, including hemophagocytic forms. Further lab abnormalities included a hypofibrinogenemia, hyperferritinemia, low complement protein C3 and C4, and hypertriglyceridemia. Patient met diagnostic criteria for HLH and was transferred to our tertiary care hospital for further management.

Given concern for tick borne disease, patient was started on doxycycline in addition to previously initiated broad spectrum antibiotics. Serum antibody testing was sent for Lyme disease, Rocky Mountain spotted fever and human Ehrlichiosis. Soluble interleukin-2-receptor alpha was found to be 2-fold increase of normal. Computed tomography of brain, chest, abdomen and pelvis were completed, negative for malignancy. Patient had rapid resolution of fever, rash, pancytopenia, improvement of mental status and respiratory status, with liberation from the ventilator within 48 hrs of treatment with addition of doxycycline. Serologic studies later returned positive with 160-fold increase in Ehrlichia IgG antibody. Ehrlichia Chaffeensis DNA was detected by PCR in the peripheral blood.

This case highlights the aggressive nature of the rare diagnosis of HLH. Prompt identification of HLH and initiation of empiric antibiotic treatment is crucial to prevent further systemic damage. Tick-borne disease is often overlooked and should highly be considered in patients in endemic regions.

BRAF V600E mutation and the tumour suppressor IGFBP7 in atypical genital naevi

BACKGROUND

Atypical genital naevi (AGN) are naevi of special sites with atypical histological features that overlap with those of malignant melanoma. Activating BRAF mutations, identified in the majority of banal melanocytic naevi and cutaneous melanomas, are reportedly uncommon in naevomelanocytic proliferations in nonsun-exposed sites. We have recently shown that constitutive activation of the BRAF-MEK-ERK signalling pathway in oncogenic BRAF-positive naevi increases expression and secretion of IGFBP7, which induces senescence and apoptosis.

OBJECTIVES

To ascertain the frequency of BRAF V600E mutations in AGN compared with banal naevi without atypia. An additional aim was to assess the expression of IGFBP7 in oncogenic BRAF-positive AGN.

METHODS

Genomic DNA was isolated per protocol from seven genital naevi without atypia and 13 AGN for BRAF genotyping. Immunohistochemical staining for IGFBP7 was performed on all cases.

RESULTS

The BRAF V600E mutation was identified in 43% of genital naevi without atypia and 23% of AGN (P = 0.61). In both groups, IGFBP7 expression was maintained in 67% of BRAF V600E-positive cases.

CONCLUSIONS

The prevalence of BRAF V600E in AGN suggests that ultraviolet exposure is not essential for generating the mutation. The BRAF V600E mutational status appears to be of limited diagnostic utility in distinguishing genital naevi that exhibit atypia from those that do not. Similar to oncogenic BRAF-positive common naevi without atypia, enhanced expression of the tumour suppressor IGFBP7 in oncogenic BRAF-positive AGN supports that they are biologically inert.

Construction and analysis of bacterial artificial chromosome libraries from a marine microbial assemblage

Cultivation-independent surveys of ribosomal RNA genes have revealed the existence of novel microbial lineages, many with no known cultivated representatives. Ribosomal RNA-based analyses, however, often do not provide significant information beyond phylogenetic affiliation. Analysis of large genome fragments recovered directly from microbial communities represents one promising approach for characterizing uncultivated microbial species better. To assess further the utility of this approach, we constructed large-insert bacterial artificial chromosome (BAC) libraries from the genomic DNA of planktonic marine microbial assemblages. The BAC libraries we prepared had average insert sizes of 80 kb, with maximal insert sizes > 150 kb. A rapid screening method assessing the phylogenetic diversity and representation in the library was developed and applied. In general, representation in the libraries agreed well with previous culture-independent surveys based on polymerase chain reaction (PCR)amplified rRNA fragments. A significant fraction of the genome fragments in the BAC libraries originated from as yet uncultivated microbial species, thought to be abundant and widely distributed in the marine environment. One entire BAC insert, derived from an uncultivated, surface-dwelling euryarchaeote, was sequenced completely. The planktonic euryarchaeal genome fragment contained some typical archaeal genes, as well as unique open reading frames (ORFs) suggesting novel function. In total, our results verify the utility of BAC libraries for providing access to the genomes of as yet uncultivated microbial species. Further analysis of these BAC libraries has the potential to provide significant insight into the genomic potential and ecological roles of many indigenous microbial species, cultivated or not.

Bacterial rhodopsin: evidence for a new type of phototrophy in the sea

Extremely halophilic archaea contain retinal-binding integral membrane proteins called bacteriorhodopsins that function as light-driven proton pumps. So far, bacteriorhodopsins capable of generating a chemiosmotic membrane potential in response to light have been demonstrated only in halophilic archaea. We describe here a type of rhodopsin derived from bacteria that was discovered through genomic analyses of naturally occuring marine bacterioplankton. The bacterial rhodopsin was encoded in the genome of an uncultivated gamma-proteobacterium and shared highest amino acid sequence similarity with archaeal rhodopsins. The protein was functionally expressed in Escherichia coli and bound retinal to form an active, light-driven proton pump. The new rhodopsin exhibited a photochemical reaction cycle with intermediates and kinetics characteristic of archaeal proton-pumping rhodopsins. Our results demonstrate that archaeal-like rhodopsins are broadly distributed among different taxa, including members of the domain Bacteria. Our data also indicate that a previously unsuspected mode of bacterially mediated light-driven energy generation may commonly occur in oceanic surface waters worldwide.

Human papillomavirus-16 E6/E7 transfected retinal cell line expresses the Müller cell phenotype

The introduction of viral transforming genes into mammalian cells has been used in establishing cultures of unlimited lifespan. Although Müller cells, the predominant glial cells in the mammalian retina, have been isolated using a variety of techniques, most of these cultures have limited capacity for cell division and are often contaminated by other cell types especially astrocytes, endothelial cells and microglial cells. We have established pure cultures of retinal cells which express Müller cell characteristics and exhibit unlimited growth in vitro. We now report the techniques involved in the propagation and characterization of these cultures. Mixed retinal cultures isolated from dystrophic rat retinas were infected with defective retroviruses coding for human papillomavirus (HPV) type 16 E6 and E7 proteins. The disabled viral constructs also contained the neomycin gene allowing selection of the cultures using Geneticin, a neomycin analogue. Pure cultures were then obtained from Geneticin-selected populations by limiting end-dilution techniques. The expression of the HPV-16 E6/E7 genes in the transfected cell line was established using an HPV-16 E6/E7 PCR product to probe Northern blots. Cloned cells were found to be highly reactive for Müller cell markers including S-100, carbonic anhydrase-C, cellular retinaldehyde binding protein, and glial fibrillary acidic protein but not for glutamine synthetase. Ultrastructural studies showed stacks of cells with long elaborate processes, short microvilli, coated pits, cytoplasmic filaments, abundant perinuclear rough endoplasmic reticulum, and smooth endoplasmic reticulum extending to the cell processes. Growth patterns of late passage cells (> 50 passages) showed a lag phase of 48 hr followed by exponential growth extending past visual confluence at day 5. Since the cultures have undergone more than 240 population doublings, they can be characterized as a continuous cell line with unlimited lifespan. The HPV-16 E6/E7 transfected Müller cell line may prove useful in studies requiring abundant and pure cultures of Müller cells.

Tuberculosis beliefs among recent Vietnamese refugees in New York State

OBJECTIVE

To identify newly arrived Vietnamese refugees' beliefs about tuberculosis (TB) and TB education needs.

METHODS

In 1994, the New York State Health Department and the Centers for Disease Control and Prevention conducted a survey of 51 newly arrived adult Vietnamese refugees in two New York counties. After being trained in interview methods, two bilingual researchers asked 32 open-ended questions on the causes of TB, TB treatment, and the disease's impact on work and social relationships.

RESULTS

Respondents correctly viewed TB as an infectious lung disease with symptoms such as cough, weakness, and weight loss. Hard manual labor, smoking, alcohol consumption, and poor nutrition were believed to be risk factors. Many respondents incorrectly believed that asymptomatic latent infection is not possible and that infection inevitably leads to disease. Nearly all respondents anticipated that having tuberculosis would adversely impact their work, family, and community activities and relationships.

CONCLUSIONS

Targeted patient education is needed to address misconceptions about TB among Vietnamese refugees and to help ensure adherence to prescribed treatment regimens.