Key Clinical MessageMutations in ARX gene should be considered in patients with mental disability or/and epilepsy. It is an X‐linked gene that has pleiotropic effects. Here, we report the case of a boy diagnosed with Ohtahara syndrome. We performed the molecular analysis of the gene and identified a new missense mutation.

Introducción: Osteopetrosis Infantil Maligna (OIM) es un grave e inusual desorden genético debido a una actividad osteoclástica anormal.Objetivo: Reportar lactante en quien se documentó una Osteopetrosis Infantil Maligna, revisando aspectos diagnósticos y terapéuticos más relevantes.Caso clínico: Reportamos un lactante de 10 meses de sexo masculino en quien se confirmó OIM tras presentar plaquetopenia y visceromegalias. En su historial destacó ser primer hijo de padres no consanguíneos, y entre sus hallazgos presentó hepatoesplenomegalia, plaquetopenia y anemia graves, compromiso sensorial visual y auditivo e infecciones a repetición. El diagnóstico fue confirmado mediante estudio genético, el cual identificó 2 mutaciones heterocigotas en el gen TCIRG1. Se realizó trasplante de precursores hematopoyéticos, sin haber presentado recuperación hematológica, falleciendo por enfermedad veno oclusiva.Discusión: La OIM es una enfermedad inusual, grave y de inicio temprano, siendo necesario un elevado índice de sospecha ante hepatoesplenomegalia y falla medular. El diagnóstico temprano y el trasplante de precursores hematopoyéticos son las únicas intervenciones potencialmente curativas de esta entidad letal.

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.