Trombocitosis en la consulta de oncohematología. Descripción, diagnóstico etiológico y evolución / Thrombocytosis in the oncology-haematology clinic: Description, aetiological diagnosis and outcome

Introducción: La trombocitosis es un motivo frecuente de consulta en oncohematología infantil, y precisa un importante número de visitas y determinaciones analíticas para su diagnóstico o resolución. Nuestro objetivo ha sido evaluar las características de los pacientes derivados a nuestro servicio en los últimos meses para estudio de trombocitosis y establecer cuáles deberían ser los pacientes que precisan un estudio más exhaustivo en el hospital. Pacientes y métodos: Se determina en 33 pacientes derivados por este motivo el sexo, el rango de edad, la procedencia, los antecedentes personales y familiares, el grado de trombocitosis por la que se consulta y la cifra máxima durante el seguimiento, el motivo por el que se realiza la primera analítica, los valores hematimétricos en la primera analítica (hemoglobina [Hb], volumen corpuscular medio [VCM], hemoglobina corpuscular media [HCM], leucocitos [linfocitos y neutrófilos]), las exploraciones complementarias realizadas, el diagnóstico y el número de visitas que precisaron antes del alta. Se clasifica la trombocitosis en leve (500-700 × 103/μl), moderada (700-900 × 103/μl), grave (900-1.000 × 103/μl) y extrema (> 1.000 × 103/μl). Resultados: No hubo predominancia de sexos. El 45 % de los pacientes eran menores de 2 años. Procedían en un 55 % de su centro de salud. La cifra media de plaquetas por la que consultaron fue de 669.000 (trombocitosis leve). En el seguimiento llegaron a cifras extremas el 24 %. En el 28 % la analítica se había realizado por un cuadro infeccioso. La exploración complementaria más solicitada fue el metabolismo del hierro (en el 82 %). Todos se corresponden con trombocitosis secundarias (el 48 % reactivas a infecciones, el 24 % secundarias a ferropenia y el 15 % por ambas causas). El número medio de visitas ha sido de 5,12. Conclusiones: El hallazgo de la trombocitosis es en la mayoría de los casos casual o en el contexto de un cuadro infeccioso y, además, son leves. Dada la baja incidencia de trombocitosis primaria en la infancia y que el diagnóstico es de exclusión, se debería iniciar el estudio de la misma en la consulta de atención primaria, descartando inicialmente una causa infecciosa, inflamatoria o secundaria a sangrado. Una vez descartadas estas causas la prueba complementaria más rentable es el metabolismo del hierro, dada la asociación de ferropenia con trombocitosis. Si también se excluye esta etiología y se comprueba la persistencia de la trombocitosis, estaría indicado derivar al paciente a un servicio de oncohematología infantil para completar estudio (AU)

Introduction: Thrombocytosis is a common cause of patient referral to a paediatric haematologist specialist which requires a significant number of laboratory tests and visits to confirm the diagnosis. The aim of our study has been to analyse the characteristics of patients referred to our centre for specialised thrombocytosis assessment. Based on this assessment we established the criteria patients must fulfil to be recommend for further hospital study. Patients and methods: We categorised the 33 patients referred for thrombocytosis assessment according to sex, age, origin, personal and family history, platelet count at diagnosis and the reason why the red and white blood count at diagnosis (Haemoglobin, mean corpuscular volume, meen corpuscular haemoglobin, leukocyte, neutrophils, lymphocyte and monocyte count), maximum platelet count during follow-up and other complementary examinations were done. The final diagnosis itself and number of previous visits before were also considered. The classification used to grade thrombocytosis was: low (500-700 × 103/μl), mild (700-900 × 103/μl), severe (900-1.000 × 103/μl) and extreme (> 1.000 × 103/μl). Results: There was no predominance of males or females. 45 % of patients were under 2 years old and 55 % of them came from their primary care centre. The mean platelet count at the first medical visit was 669,000 (mild thrombocytosis). During follow-up, 24 % of the patients reached extreme platelets levels. In 28 % the initial blood count was performed because of an infection. The most frequently requested laboratory test was iron metabolism (82 % of the cases). All cases correspond to secondary thrombocytosis (48 % were reactive to infections, 24 % secondary to iron deficiency, and 15 % were associated to both causes). The mean number of visits before hospital discharge was 5.12. Conclusions: The finding of thrombocytosis in the majority of the cases studied was casual or in the context of an infectious process. Most of the thrombocytosis were mild. Due to the extremely low incidence of primary thrombocytosis in childhood and the fact that diagnosis is made by exclusion of other possibilities, the initial study of these patients should be done in primary care centres. The first conditions to be ruled out are infectious, inflammatory or bleeding processes. Once these causes are excluded, the most useful complementary test is to measure iron level given the relation between iron deficiency and thrombocytosis. Once these causes are ruled out and thrombocytosis persists, it would then be indicated to refer the patient to a paediatric oncology-haematology department for a more exhaustive follow-up (AU)

Transgenic mice overexpressing human c-mpl ligand exhibit chronic thrombocytosis and display enhanced recovery from 5-fluorouracil or antiplatelet serum treatment.

The consequences of long-term in vivo expression of human c-mpl ligand in a mouse model were examined. Transgenic mice expressing the human full-length cDNA in the liver exhibited a fourfold increase in circulating platelet count that persisted stably over the life of the animals. Transgenic animals thrived and appeared healthy for at least 500 days. Transgenic platelets appeared normal with respect to surface antigens and response to platelet aggregation agonists. The highest-expressing transgenic line maintained human c-mpl ligand serum levels of 3 ng/mL. Megakaryocyte numbers in bone marrow and spleen were elevated, as were bone marrow and spleen megakaryocyte colony-forming cells (MEG-CFC). Megakaryocytes were observed in the bone marrow, spleen, liver, and lung, but in no other sites. Circulating myeloid and lymphoid cell populations were increased twofold. Additionally, the animals had a slight but significant anemia despite an increase in marrow colony-forming units-erythroid (CFU-E). No evidence of myelofibrosis was observed in the bone marrow. The platelet nadir in response to administration of either antiplatelet serum (APS) or 5-fluorouracil (5FU) was significantly reduced relative to the control level. Furthermore, the red blood cell (RBC) nadir was reduced relative to control levels in both models, suggesting that c-mpl ligand can directly or indirectly support the maintenance of erythrocyte levels following thrombopoietic insult.