Orbital Involvement in Acute Adult Leukemias: Case Series and Review of Literature.

Orbital involvement in acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) is well-described in children but is uncommon in adults. This series reports 2 adult patients with orbital leukemic involvement and summarizes the existing literature. A 37-year-old male with recently diagnosed AML underwent induction therapy and subsequently developed a tan-pink colored sub-conjunctival lesion in the left eye. Incisional biopsy confirmed AML. A 35-year-old male with history of ALL presented with left-sided orbital mass. Fine needle aspiration biopsy confirmed ALL. Literature review of adult-onset orbital leukemia yielded 29 cases of AML and 3 cases of ALL. Orbital involvement of acute adult-onset leukemia tends to be unilateral, presents in the extraconal space and can occur at any point during systemic leukemic disease. Chemotherapy is the mainstay of treatment, often in combination with radiation and/or hematopoietic stem cell transplant.

Orbital manifestations of B-cell acute lymphoblastic leukemia/lymphoma.

A 2-year-old boy presented with left periorbital edema, proptosis, hyperglobus and esotropia. Imaging revealed an inferotemporal orbital mass with adjacent bony erosion. Histological evaluation of an orbital biopsy revealed B-cell acute lymphoblastic leukemia/lymphoma (B-ALL/BLL). The patient was subsequently treated with chemotherapy. Although orbital involvement in acute myelogenous leukemia has been well-described, orbital manifestations of B-ALL/BLL are uncommon, with only a limited number of previous reports in the literature.

Comparison of laboratory methods for the detection of neoplastic plasma cells in plasma cell dyscrasias.

AIMS: To compare the ability of immunohistochemistry (IHC), multiparameter flow cytometry (MFC) and fluorescence in situ hybridisation (FISH) to detect clonal plasma cells. We also attempted to outline a testing strategy for monitoring multiple myeloma patients. METHODS: A retrospective review was performed on 278 CD138+sorted FISH studies from November 2019 to December 2020 along with their concurrent IHC and MFC results. A p value was computed using McNemar's test for paired data. Association was calculated using the non-parametric Spearman correlation coefficient. RESULTS: Using the Mc Nemar's test for paired data, CD138+sorted FISH studies achieved the highest proportion of positive results and was significantly greater than MFC (63% vs 53%, p=0.01). FISH had more positive results than IHC, although this did not reach statistical significance (60% vs 57%, p=0.34). IHC and MFC had high correlation and high agreement (90.3% agreement, kappa=0.805, p<0.0001). CD138+sorted FISH studies achieved the highest proportion of positive results relative to IHC and MFC, indicating that it may be a reliable marker for clonal plasma cell detection. CONCLUSIONS: While CD138+sorted FISH is primarily used for prognostication, it may be employed as a single test for detection and monitoring clonality in certain scenarios. Further studies are needed to monitor the outcomes of patients with positive FISH and negative IHC and MFC. Additionally, there was high agreement between IHC and MFC, suggesting that performing both tests may not be necessary.

Heterochromatin-mediated gene silencing facilitates the diversification of olfactory neurons.

An astounding property of the nervous system is its cellular diversity. This diversity, which was initially realized by morphological and electrophysiological differences, is ultimately produced by variations in gene-expression programs. In most cases, these variations are determined by external cues. However, a growing number of neuronal types have been identified in which inductive signals cannot explain the few but decisive transcriptional differences that cause cell diversification. Here, we show that heterochromatic silencing, which we find is governed by histone methyltransferases G9a (KMT1C) and GLP (KMT1D), is essential for stochastic and singular olfactory receptor (OR) expression. Deletion of G9a and GLP dramatically reduces the complexity of the OR transcriptome, resulting in transcriptional domination by a few ORs and loss of singularity in OR expression. Thus, our data suggest that, in addition to its previously known functions, heterochromatin creates an epigenetic platform that affords stochastic, mutually exclusive gene choices and promotes cellular diversity.

Enhancer interaction networks as a means for singular olfactory receptor expression.

The transcriptional activation of one out of ?2800 olfactory receptor (OR) alleles is a poorly understood process. Here, we identify a plethora of putative OR enhancers and study their in vivo activity in olfactory neurons. Distinguished by an unusual epigenetic signature, candidate OR enhancers are characterized by extensive interchromosomal interactions associated with OR transcription and share a similar pattern of transcription factor footprints. In particular, we establish the role of the transcription factor Bptf as a facilitator of both enhancer interactions and OR transcription. Our observations agree with the model whereby OR transcription occurs in the context of multiple interacting enhancers. Disruption of these interchromosomal interactions results in weak and multigenic OR expression, suggesting that the rare coincidence of numerous enhancers over a stochastically chosen OR may account for the singularity and robustness in OR transcription.

An epigenetic trap stabilizes singular olfactory receptor expression.

The molecular mechanisms regulating olfactory receptor (OR) expression in the mammalian nose are not yet understood. Here, we identify the transient expression of histone demethylase LSD1 and the OR-dependent expression of adenylyl cyclase 3 (Adcy3) as requirements for initiation and stabilization of OR expression. As a transcriptional coactivator, LSD1 is necessary for desilencing and initiating OR transcription, but as a transcriptional corepressor, it is incompatible with maintenance of OR expression, and its downregulation is imperative for stable OR choice. Adcy3, a sensor of OR expression and a transmitter of an OR-elicited feedback, mediates the downregulation of LSD1 and promotes the differentiation of olfactory sensory neurons (OSNs). This novel, three-node signaling cascade locks the epigenetic state of the chosen OR, stabilizes its singular expression, and prevents the transcriptional activation of additional OR alleles for the life of the neuron.