Human T-lymphotropic virus type 1 (HTLV-1) infection is asymptomatic in most carriers; however, approximately 5% of infected individuals may develop adult T-cell leukemia/lymphoma (ATLL), a rare and highly aggressive malignancy with poor prognosis. We report a case of acute-type ATLL in an elderly patient from the Brazilian Amazon that was initially suspected to be T-cell lymphoblastic lymphoma, resulting in diagnostic delay. Peripheral blood and bone marrow examinations revealed marked lymphocytosis with characteristic "flower cells," prompting serological testing for HTLV-1. Infection was confirmed by chemiluminescent immunoassay and western blot. The diagnosis was established at the state reference hematology center, highlighting the critical role of cytomorphologic evaluation in endemic regions where HTLV-1 remains underdiagnosed. We additionally present a narrative review of reported ATLL cases in Latin America, emphasizing the frequency of acute presentations, high mortality rates, and diagnostic challenges posed by overlapping immunophenotypic features with other aggressive T-cell neoplasms. This case underscores the importance of maintaining a high index of suspicion for HTLV-1-associated ATLL in tropical settings and reinforces the need for improved diagnostic surveillance in the Brazilian Amazon.

Pertussis is a common infectious disease affecting both children and adults. In young infants, it can cause severe respiratory illness associated with prolonged hospitalization and high mortality, particularly in cases complicated by severe leukocytosis and lymphocytosis, which increase the risk of pulmonary hypertension and multiorgan failure. Exchange transfusion remains the traditional first-line treatment for severe pertussis-associated hyperleukocytosis. However, in centers with appropriate resources and expertise, leukapheresis may be considered as an alternative therapeutic option. Leukapheresis enables selective reduction of circulating white blood cells, which are thought to play a central role in the pathophysiology of severe pertussis, while avoiding exposure to allogeneic blood products. It may also result in incidental platelet removal, potentially reducing blood viscosity and thrombotic risk in patients with concomitant thrombocytosis. Despite these potential advantages, leukapheresis is technically demanding and should be performed only in experienced centers with established protocols and appropriate expertise. Through the apheresis system we treated two patients who developed malignant pertussis with which successfully decreased their WBC counts by more than 50%. In the presence of limited guidance in the current literature regarding its prescription, usage, and safety specifically in pertussis, this report provides additional insights into the prescription and implementation of an effective leukocyte depletion.

Stroke mimics represent a major diagnostic challenge in the hyperacute setting. We report the case of a 29-year-old woman with no prior documented history of migraine or clinically significant headache who developed sudden-onset bradylalia and right hemisensory paresthesias, rapidly progressing to severe mixed aphasia with motor predominance, jargonaphasia, anomia, dysgraphia, alexia, and involuntary mixing of three languages. The initial National Institutes of Health Stroke Scale (NIHSS) score was five, accompanied by headache and vomiting. Intense agitation required procedural sedation for CT acquisition. Motion artifact rendered perfusion maps non-interpretable. Non-contrast CT showed no hemorrhage or established infarct (Alberta stroke programme early CT score (ASPECTS) 10), and CT angiography demonstrated no large vessel occlusion. Given the disabling neurological deficit and symptom onset within the therapeutic window, intravenous tenecteplase 17.5 mg was administered. Neurological recovery was complete within hours, and the delayed brain MRI was normal. Headache with Neurological Deficits and Cerebrospinal Fluid Lymphocytosis (HaNDL) syndrome remained an unconfirmed diagnostic consideration. Ultimately, the episode was assessed as a probable stroke mimic, most consistent with migraine with aphasic aura. This case illustrates that intravenous thrombolysis may be clinically justifiable under reasonable diagnostic uncertainty when the deficit is severe, the therapeutic window is favorable, and imaging is technically limited, followed by cautious post-acute diagnostic reorientation.

Because T cell neoplasms often present with nonspecific findings, T cell clonality assessment is performed across many clinical scenarios, including the workup of cytopenias, lymphocytosis, eosinophilia, and suspected lymphoma. Sensitive assays, including flow cytometric staining of the T cell receptor (TCR) constant region and molecular-based TCR clonality testing, have enhanced our ability to detect T cell neoplasms, but these techniques frequently identify T cell clones in patients without suspicion of T cell malignancy. These incidentally detected clones, sometimes called T cell clones of uncertain significance (TCUS), do not clearly have universal potential for progression to overt T cell neoplasia. However, their detection can prompt unnecessary diagnostic procedures, generate unwarranted patient anxiety, and even lead to inappropriate therapeutic interventions. Here, we propose a practical framework for risk stratification of unexpected T cell clones in peripheral blood that minimizes the risk of unnecessary intervention while maintaining vigilance for true T cell malignancy.

Sprue-like enteropathy associated with angiotensin II receptor blockers (ARBs) is a rare cause of chronic diarrhea and malabsorption, typically characterized by villous atrophy and intraepithelial lymphocytosis mimicking celiac disease. Although olmesartan is the most frequently implicated agent, cases associated with other ARBs, including losartan, have increasingly been recognized. A 61-year-old woman with hypertension treated with losartan for three years presented with a three-month history of abdominal pain and chronic diarrhea. Upper endoscopy revealed a macroscopically and histologically normal duodenum. Colonoscopy demonstrated macroscopically normal ileal mucosa; however, ileal biopsies showed villous atrophy and marked intraepithelial lymphocytosis. Celiac serology was negative, infectious causes were excluded, and vitamin B12 deficiency was documented. In the setting of chronic exposure to losartan and after exclusion of alternative etiologies, ARB-associated sprue-like enteropathy was suspected. Losartan was discontinued and replaced with amlodipine, resulting in complete clinical resolution. This case highlights an atypical presentation of losartan-induced sprue-like enteropathy with isolated ileal involvement and a histologically normal duodenum. Clinicians should consider this entity in patients presenting with chronic diarrhea and seronegative villous atrophy, even in the absence of duodenal involvement.

A 3-month-old male Bernese Mountain dog was presented with a 10-day history of vomiting, vocalisation and abdominal discomfort following vaccination. Physical examination revealed subtle peripheral lymphadenopathy. Haematological testing revealed borderline anaemia, thrombocytopenia and moderate lymphocytosis with a high proportion of reactive or atypical lymphocytes. Cytology of the spleen and lymph nodes showed lymphoid hyperplasia, and PCR for antigen receptor rearrangement confirmed a polyclonal lymphocyte population with no evidence of clonal rearrangements of immunoglobulin or T-cell receptor genes. No treatment was initiated. Follow-up testing demonstrated spontaneous resolution of haematological abnormalities and normalisation of cytology within 30 days. Although causality cannot be established, a transient antigenic stimulation temporally associated with recent vaccination was considered among the possible explanations. This report highlights the importance of recognising benign reactive lymphocytosis that may mimic lymphoproliferative disease in young dogs.

Low-normal serum immunoglobulin (Ig) levels may reflect early immune dysregulation preceding chronic lymphocytic leukemia (CLL), but their prognostic significance years before diagnosis is unclear. We conducted a large retrospective cohort study, including 294,712 adults aged 40-80 years with routine Ig testing and up to 10 years of follow-up. Immunoglobulin G (IgG), A (IgA), and M (IgM) levels were assessed a decade before diagnosis and dichotomized at the median values observed in individuals who later developed CLL. Multivariable Cox regression was performed, with sensitivity analyses stratified by baseline lymphocyte counts to distinguish constitutional effects from occult monoclonal B-cell lymphocytosis (MBL). Low-normal IgA (< 187 mg/dL) demonstrated the strongest association with future CLL (adjusted hazard ratio [aHR] 2.62), followed by IgM (aHR 1.77) and IgG (aHR 1.43). In individuals with low-normal lymphocyte counts, IgM and IgG lost predictive value, whereas IgA remained independently associated with CLL risk. Dose-response analyses revealed steep monotonic gradients across the normal range. Temporal analyses demonstrated that IgA-associated risk extended beyond a decade prior to diagnosis, while IgM and IgG associations attenuated earlier. These findings support a dual-mechanism model in which low IgM and IgG reflect tumor burden from undiagnosed MBL, whereas low IgA identifies a constitutional susceptibility phenotype.

Angiostrongyliasis is a parasitic disease caused by Angiostrongylus costaricensis (Latin America) and A. cantonensis (Asia/Pacific). Abdominal angiostrongyliasis often mimics appendicitis, challenging clinical diagnosis and requiring histopathological confirmation. We report a severely malnourished infant in Honduras presenting with 10 days of severe abdominal pain and vomiting, complicated by respiratory insufficiency and seizures. Brain CT revealed cortical atrophy, suggesting a chronic underlying neurologic condition. Laboratory tests showed leukocytosis, lymphocytosis, and massive eosinophilia. Exploratory laparotomy for suspected appendicitis identified an ileal perforation, requiring intestinal resection. Histopathology confirmed non-caseating granulomas containing A. costaricensis larvae within the mesenteric arteriovenous plexus, alongside scattered eggs. This is the first confirmed human case of abdominal angiostrongyliasis with suspected, unconfirmed extraintestinal involvement in the Olancho Department of Honduras. These findings emphasize the critical need for increased clinical awareness and public health measures against this overlooked parasitic infection.