Monoclonal B-cell lymphocytosis (MBL) is an asymptomatic condition in which individuals have increased blood levels of particular subtypes of monoclonal lymphocytes (i.e. an aberrant and potentially malignant group of lymphocytes produced by a single ancestral cell).
[9] These associations strongly suggest that inheritable genomic abnormalities contribute to the development of CLL/SLL MLB and, possibly, the progression of this disorder to CLL/SLL.
[9][11] Chromosome abnormalities, single nucleotide polymorphisms (SNPs, i.e. substitutions of a single nucleotide in a DNA sequence at a specific position in the genome) and gene mutations, while each occurs in <15% of cases,[12] are present in CLL/SLL MBL and to some extent are similar to those found in CLL/SLL.
[citation needed] The cited studies suggest that there is a step-wise accumulation of genomic abnormalities that lead to CLL/SLL MBL and MBL-MZ and then to overt malignancy.
Herpes Zoster and various upper respiratory tract infections are also considered to be risk factors for developing CLL/SLL MBL.
It seems possible that the pathogens involved in these diseases provide antigens that stimulate the development of MBL although further studies are required to explore this hypothesis further.
It therefore appears that CLL/SLL and, by implication, CLL/SLL MBL have little or no ability to be transmitted by blood transfusions, at least when the donors and recipients are unrelated.
[3] However, individuals with CBL-MZ commonly present with B-cell blood counts that are extremely high (>4.0x109; range 3.0x109/L to 37.1x109/L);[2] and may have an IgM monoclonal gammopathy.
[6] Most individuals with MBL have at presentation an abnormal infiltrate of monoclonal B-cells in their bone marrow as determined by biopsy.
[3] MBL patients may present with asymptomatic lymphadenopathy (i.e. lymph nodes that are enlarged or abnormal in consistency).
However, patients who have grossly enlarged (i.e. >1.5 centimeters) (cm) lymph nodes on physical examination do have a greater risk of progression.
However, patients with these autoimmune disorders who have very small B cell clones either never develop a lymphocyte malignancy or, rarely, do so and only after many years.
Consequently, it is now widely recognized that such cases, when associated with very small numbers of monoclonal B-cells, are best diagnosed as CLL/SLL MBL with autoimmune cytopenia rather than CLL/SLL.
While the significance of these lesions is unknown, the presence of extensive infiltrations that replace normal tissue is more consistent with a diagnose of CLL/SLL than CLL/SLL MBL.
The key cell markers and other points that help distinguish the following MBL phenotypes from these malignancies include the following (refer to Table for comparisons to non-malignant predecessor cells): In situ lymphoid neoplasia (ISLN), a lymphocyte disorder newly categorized by the World Health Organization (2016,) has several features in common with MLB.
[citation needed] Individuals with high-count MBL (studies based primarily on the CLL/SLL phenotype) are at an increased risk for developing: 1) cancers of the breast, lung, and gastrointestinal tract in up to 13% of all cases; 2) autoimmune hemolytic anemia and immune thrombocytopenic purpura; 3) unexplained kidney disease as manifested by chronic kidney disease and/or the nephrotic syndrome; and 4) serious infections.
[2] In addition to having very high numbers of B-cells, high-count CLL/SLL MLB patients whose monoclonal B cell clone lacks mutions in IGVH genes (see above section on genome abnormalities) or whose |β2 macroglobulin is elevated have a shorten survival.
Rather, this shortened survival appears due to the disorders' susceptibility to serious infections, other types of cancers, immune cytopenias, and renal disease.
[2] Recommended treatments for patients with high-count MBL[9] and MBL-MZ[6] include yearly follow-up evaluations to test for the malignant progression of their disorder and for the development of other forms of cancer, infections, immune cytopenias, and renal disease.
It may also be beneficial to ensure that high-count MLB patients are up to date on vaccinations including those for influenza, pneumococcal pneumonia, and tetanus before they become more severely immunocompromised by the progression of their disorder.