Immunophenotypic challenges in diagnosis of CD79a negativity in a patient with B acute lymphoblastic leukemia harboring intrachromosomal amplification of chromosome 21: a case report.

BACKGROUND: Being expressed in all stages of B-cell development and having a significant value on the European Group for the Immunological Characterization of Acute Leukemias scoring system, CD79a is considered as an excellent pan-marker for lineage assignment of B cells by flow cytometry. Therefore, any lack or decrease in CD79a expression makes the diagnosis of B acute lymphoblastic leukemia cases very challenging, especially in developing country laboratories where flow cytometry analyses are not always available and, when they are, they are limited in the number of markers used for lineage assignment. Since this case is potentially interesting, we report a B acute lymphoblastic leukemia case with a lack of expression CD79a associated with intrachromosomal amplification of chromosome 21 genetic abnormality. We further discuss the practical challenges in the diagnosis of this case. CASE PRESENTATION: We present the case of an 8-year-old Caucasian boy from eastern Morocco who was initially hospitalized for a hemorrhagic syndrome. Peripheral blood smear examination showed a significant number of blasts suggesting acute leukemia. Bone marrow was studied for morphology, cytochemistry, immunophenotyping, and cytogenetics. Flow cytometry analyses showed expression of CD19, CD22, CD10, CD34, and HLA-DR markers by leukemic blasts. The expression of CD79a, which was checked with two different monoclonal antibodies, confirms that this marker was severely decreased in this case. Cytogenetic study performed by fluorescence in situ hybridization revealed the presence of intrachromosomal amplification of chromosome 21, a cytogenetic abnormality that is specific for B acute lymphoblastic leukemia. CONCLUSION: CD79a is one of the critical markers in the assignment of B acute lymphoblastic leukemia. In our case, we were lucky enough to be assisted by a few other markers of the B lineage that were positive in this case. Also, we mention the importance of proceeding to cytogenetic study, which in our case helped us to confirm the diagnosis made by flow cytometry by highlighting a cytogenetic abnormality that is specific to B acute lymphoblastic leukemia.

Serious phlegmonous lesion of the hand following an injury by vegetal thorn: Never forget Pasteurella multocida!

Pasteurella multocida can cause serious infections after dog or cat bite. We report here a rare case of hand infection caused by P. multocida consecutive to an injury by a thorn of the prickly pear. It caused an amputation of the distal phalanx of the thumb in a trisomic patient. It is about a 27-year-old man who was admitted to the hospital with swelling and intense pain of the left hand. He reported a sting by a thorn of prickly pear 15 days before. The patient was admitted to proceed with operative irrigation and debridement. The pus was collected for microbiological examination. Microscopic examination after Gram staining revealed small Gram-negative coccobacilli, associated to polymorphonuclear reaction. Culture have objectivated Pasteurella multocida. The isolated strain was susceptible to betalactamins. Patient was treated with ampicillin. Well-conducted antibiotics and repetitive local cares have not prevented local lesions from progressing to necrosis of the soft parts of the thumb and osteitis of the distal phalanx of the thumb. The patient underwent a necrosectomy and an amputation of the distal phalanx. Ampicillin was replaced by amoxicillin/clavulanic acid and after 15 days, progression was clinically and microbiologically favorable. In the case we report, since the patient does not report any exposure or contact with animals, the thorn prick is the source of infection. It was contaminated from the animal reservoir. Taking into account the monomicrobism of the infection, treatment with aminopenicillins was sufficient. Our propositus came to the hospital 15 days after the inoculation of the bacterium. This duration appears to be very late in relation to the acute character of pasteurellosis. This was probably the main reason why the local infection evolved towards osteoarticular complications. That's why, we should consider Pasteurella multocida in case of infection by inoculation, even in the absence of contact with the animals.