Multisystem Inflammatory Syndrome in Children (MIS-C) is a new entity with association with SARS-CoV2. Clinical features of Kawasaki disease (KD) were noted from the first reported cases of MIS-C. Before the COVID-19 pandemic, Kawasaki disease shock syndrome (KDSS) was considered to be a distinct and unique form of KD. We present a representative case which prove the current difficulty in clearly distinguishing MIS-C from Pre-COVID-19-KDSS and emphasize the overlap of the diagnostic criteria.

In 2021, 273 Rocky Mountain spotted fever cases were reported nationwide in Mexico. In Chihuahua City, fourteen samples were obtained from children suspected of rickettsial infection. The analysis of samples (January to December 2021) showed prevalence rates of 28.5%, 43%, and 28.5% for Rickettsia rickettsii, Ehrlichia canis, and both pathogens in coinfection, respectively. The analysis of clinical haematological and biochemistry analytes showed alterations; 100% of the children had elevated liver enzymes and coagulation times, 64% showed leukocytosis due to neutrophilia, 55% had thrombocytopenia, lymphopenia, and hypoalbuminemia, and 45% showed normocytic normochromic anaemia. Statistically significant differences were observed in the expression of the chemokines IL-8, RANTES, CXCL9/MIG, and CXCL10/IP-10 across the coinfected and control groups, and the difference in IP-10 expression was significant for patients infected by R. rickettsii compared to the control group. Additionally, significant differences were observed for expression levels of IL-1β, IL-6, IL-17, IFNγ, and TNFα among the R. rickettsii-positive group compared to the control group. On the other hand, the coinfected group exhibited modified levels of IL-6, IL-8, and IL-10 compared with the control group. Finally, significant differences were observed for CD8+ T lymphocyte subpopulations between individuals positive for R. rickettsii and those positive for E. canis.

In 2021, 273 Rocky Mountain Spotted Fever cases have been reported nationwide. In Chihuahua City, fourteen samples were obtained from children suspected of rickettsial infection. The analysis of samples collected from January to December 2021 showed a prevalence of 28.5%, 43% and 28.5% for Rickettsia rickettsii , Ehrlichia canis , and both pathogens in coinfection, respectively. The analysis of clinical hematological and biochemistry analytes showed alterations such as 100% of the children coursed with elevated liver enzymes and coagulation times, 64% showed leukocytosis due to neutrophilia, 55% of them had thrombocytopenia, lymphopenia and hypoalbuminemia, and 45% showed normocytic normochromic anemia. Statistically significant differences were obtained in the chemokines IL-8, RANTES, CXCL9/MIG, and CXCL10/IP-10 across the coinfected and control groups; the differences in IP-10 were significant for patients infected by R. rickettsii compared to the control group. Also, significant differences were observed for IL-1β, IL-6, IL-17, IFNγ, and TNFα among the R. rickettsii positive group compared to the control group; on the other hand; the coinfected group exhibited modified levels of IL-6, IL-8, and IL-10 compared with the control group. Finally, significant differences were obtained for CD8 + T lymphocytes subpopulations between positive individuals for R. rickettsii and E. canis.

The intracellular pathogen Rickettsia rickettsii causes tick-borne spotted fever (also called Rocky Mountain spotted fever (RMSF) and is increasingly recognized as an emerging cause of febrile illness in Mexico. However, little is known about the early immune responses to infection. Four RMSF pediatric patients on acute phase and eight healthy controls from Chihuahua, Mexico were recruited. The natural killer cell (NK) immunophenotype and the cytokine profile in peripheral blood were characterized by flow cytometry. The population of cytotoxic NK cells expressing NKG2D was significantly decreased in patients on 3rd day of hospitalization compared to the first sampling on admission. Interleukins IL-6, IL-8, and IL-10 levels were significantly increased in patients upon admission compared to controls. This study shows that circulating NK cells are numerically decreased, while cytokines induce a pro-inflammatory process in patients.