Background: Primary meningococcal arthritis (PMA) is defined as the presence of acute septic arthritis with the identification of Neisseria meningitidis in synovial fluid or blood cultures but no clinical evidence of sepsis or meningitis. This report aimed to describe a clinical case of PMA caused by serogroup W, an uncommon etiology of this disease in Uruguay, and review the available literature. Case report: We report the case of a 5-year-old female, with no past medical history, admitted to the emergency department with a 12-hour history of fever of 39 °C and a limp. The patient was hemodynamically stable and had no clinical evidence of meningitis. Hip ultrasound showed an increase in synovial fluid. Arthrocentesis showed purulent exudate and synovial fluid culture showed no growth after five days. The blood culture showed isolates of N. meningitidis, serogroup W. The patient received treatment with ceftriaxone, and drainage of the affected joint was performed with excellent clinical response. Conclusions: Primary meningococcal arthritis is a rare presentation of meningococcal disease. Systematic arthrocentesis and the adequacy of antibiotic therapy when septic arthritis is clinically suspected are essential for confirming the diagnosis and decompressive drainage of the involved joint. This report is the first of PMA caused by serogroup W in Uruguay. Although the most common serogroup involved in meningococcal arthritis is serogroup B in Uruguay, an increase in serogroup W-related diseases has been reported in Chile and Argentina, emphasizing the need for epidemiological surveillance.

Background: Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant disease affecting connective tissue, primarily caused by de novo mutations of the ACVR1 gene. FOP is a disease with congenital malformations of the toes and heterotopic ossification in characteristic patterns that progresses with flare-ups and remissions. Cumulative damage results in disability and, eventually, death. This report aimed to describe a case of FOP to highlight the importance of early diagnosis of this rare condition. Case report: We describe the case of a 3-year-old female diagnosed with congenital hallux valgus, who initially presented with soft tissue tumors, predominantly in the neck and chest, with partial remission. Multiple diagnostic tests were performed, including biopsies and magnetic resonance imaging, with nonspecific results. We observed ossification of the biceps brachii muscle during evolution. The molecular genetic study found a heterozygous ACVR1 gene mutation that confirmed FOP. Conclusions: Knowledge of this rare disease by pediatricians is critical for an early diagnosis and for avoiding unnecessary invasive procedures that may promote disease progression. In case of clinical suspicion, performing an early molecular study is suggested to detect ACVR1 gene mutations. The treatment of FOP is symptomatic and focused on maintaining physical function and family support.

En los lactantes, el déficit de vitamina B12 se debe fundamentalmente a carencias nutricionales vinculadas a déficit materno. La mayoría de los casos de déficit materno se vinculan a dietas vegetarianas. La anemia perniciosa es una enfermedad autoinmune que compromete la absorción de esta vitamina, aunque menos frecuente que la carencia nutricional, es también una causa importante de déficit materno. Objetivo: reportar un caso de déficit de vitB12 en un lactante, secundario a anemia perniciosa en su madre, y revisar los aspectos más importantes de esta enfermedad en la infancia. Caso Clínico: Lactante de 9 meses, de sexo masculino, sin antecedentes perinatales patológicos, alimentado con lactancia materna, con rechazo persistente a la incorporación de alimentos sólidos desde los 6 meses. Un mes previo a la consulta, comenzó progresivamente con hiporreactividad, con fluctuación del estado de conciencia, regresión de conductas motoras y vómitos. El hemograma mostró anemia macrocítica y neutropenia. Se confirmó el déficit de vitamina B12 en el lactante. Recibió tratamiento con vitamina B12 intramuscular con buena evolución clínica y de los exámenes de laboratorio. Se confirmó el déficit materno de B12 como causa del déficit en el lactante. No existían restricciones en la dieta materna, por lo que se midieron en la madre los anticuerpos anti factor intrínseco y anti célula parietal que resultaron positivos, diagnosticándose anemia perniciosa. Conclusiones: El reconocimiento precoz es fundamental para prevenir el desarrollo de daño neurológico potencialmente irreversible. La anemia perniciosa materna debe ser considerada en el caso de niños con anemia megaloblástica, principalmente en aquellos cuyas madres no tengan dietas vegetarianas.