Septic arthritis of the shoulder caused by E. coli infection in a premature infantPresentamos el caso de un prematuro de 33 semanas y 1600 g, con antecedente de traslado en las primeras 12 horas de vida a la Unidad de Cuidados Intensivos Neonatales de un hospital terciario por hipertensión pulmonar grave y afectación multiorgánica, que a su regreso a nuestro centro a las 37 semanas corregidas comienza con decaimiento y pausas de apnea. Tras un inicio de cuadro subagudo e inespecífico, con alteraciones analíticas discretas, presenta progresivamente tumefacción, dolor e impotencia funcional del hombro derecho. Se realiza el diagnóstico de artritis séptica del mismo tras evidenciar derrame articular por ecografía y obtener líquido articular purulento en la punción-aspiración. Recibe precozmente antibioterapia empírica, que se ajusta al antibiograma una vez que se conoce que crece un E. coli sin resistencias en el líquido articular. La mejoría es inicialmente lenta pero, tras tres semanas de antibioterapia intravenosa sin necesidad de cirugía abierta, la recuperación es franca aunque no total. Completa otras tres semanas de antibioterapia oral con cefuroxima-axetilo en dosis altas. La evolución en su seguimiento es adecuada, con normalización y desaparición del derrame articular a los cinco meses de edad.We present the case of a premature infant 33 weeks of gestational age and 1600 g, that had required intensive care at a tertiary hospital due to refractory pulmonary hipertensión and multiorganic illness, at his return to our center, at 37 weeks of corrected gestational age, with a peripheral line in his right axilla, presents with frequent apneas and feeding intolerance. The initial presentation is subacute and unspecific, with discrete alterations in his blood tests, but progressively starts with inflammatory signs, pain and shoulder movement limitations. Septic arthritis is diagnosed after revealing joint effusion by ultrasonography and obtaining synovial fluid with purulent characteristics by needle aspiration. He was started on empiric intravenous antibiotics that were later adjusted according to the antibiogram once the results for the synovial fluid culture turned positive for E. coli. Clinical recovery was slow at first, but clearly improved throughout a three week intravenous antibiotic course, and the infant did not need open surgery. At discharge, there was an almost full recovery in terms of movement range of the shoulder and he was pain free. The infant completed another three weeks of oral antibiotics with cefuroxime-axetile. Ongoing follow-up yielded excellent results.