Erythema nodosum associated with Shigella colitis in a 7-year-old boy

There are only three reported cases of erythema nodosum being caused by Shigella infections in the literature and only one of these occurred in a pediatric patient. We report the first pediatric case of post-infective erythema nodosum due to Shigella flexneri in Europe and in the youngest known patient to date. A 7-year-old boy was admitted with a five-day history of vomiting and watery diarrhea. Over the previous few days fresh blood and mucus was noted in the stool. The frequency of stool passage was 2—3 stools/hour and was associated with both perianal and abdominal pain. The rest of the family remained well and there was no history of recent travel, uncooked meat, or infectious contacts. The patient was an immunocompetent child who was growing and developing normally. There was history of fatigue but no fever. He was afebrile and well hydrated with normal examination. Initial sodium was 131 mmol/l, potassium 3.7 mmol/l, urea 8.0 mmol/l, creatinine 58 mmol/l, and C-reactive protein 69 mg/l. The total white blood cell count was 5.35 10/l, neutrophil count 3.28 10/l with normal liver function tests and coagulation. Stool cultures were positive for Shigella flexneri. Supportive management with oral rehydration fluid and analgesia commenced. Six days later, the patient complained of itchy eyes. However eye and joint examination were normal and he was discharged home on day six when abdominal pains had ceased. On day 16, the family raised concerns regarding a rash on the extensor areas of both upper and lower limbs. Examination revealed florid erythema nodosum with discrete macular-papular, erythematous, warm and tender nodules. The nodules were bilaterally distributed ranging from 1 to 5 cm in diameter. They lasted a couple of weeks and were treated symptomatically with non-steroidal anti-inflammatory medication. They did not recur. Shigella is a global human health problem particularly in developing countries. In Europe, children in day-care centers or ofmigrant families aremost at risk. Thepredominantmode of transport is fecal—oral contact and low infectious inoculums (as few as 10 organisms) makes it highly contagious. The organism generally survives poorly in the environment. S. flexneri is the hyperendemic species in developing countries and is responsible for approximately 10% of all diarrheal episodes among young children. The species is highly fragile and may be missed unless care is taken in collection and handling. The infection commences with fever, fatigue, malaise, and anorexia and progresses to watery diarrhea before dysentery. Persistent diarrhea and malnutrition are the most common sequelae. A rare post-infectious complication seen mainly in adults is reactive inflammatory arthritis or in combinationwith conjunctivitis and urethritis (Reiter’s syndrome). Erythema nodosum has an acute onset, characterized by erythematous, tender, warm nodules, and raised plaques usually located on the shins, ankles, and knees. Initially nodules are bright red but within days become livid red or purplish and finally turn to yellow/green. The list of etiological factors is varied. Inflammatory bowel disease, Yersinia enterocolitica, Salmonella typhimurium, and Campylobacter jejuni gastroenteritis have all been described in an etiological relationship with the development of post-infective erythema nodosum. In this case the chronologic correlation between the appearance of S. flexneri and that of erythema nodosum makes it likely that the two were etiologically related with no evidence of other precipitants present. Resolution is spontaneous within a few weeks and non-steroidal anti-inflammatory medication is helpful. Shigella infection in the European pediatric population is uncommon. The species is fragile and this may explain why there is limited literature proposing the link between the infection and erythema nodosum. This case provides further evidence to support this association. Conflict of interest: No conflict of interest to declare.