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Sodium polystyrene sulfonate (PSP) or Kayexalate is a cation-exchange resin, widely used in the management of hyperkalaemia due to renal disease. A rare, yet potentially dangerous, adverse event related to sodium polystyrene sulfonate use is intestinal mucosal injury, especially in the colon. The injury to the gastrointestinal mucosa can range from mild and superficial to wall necrosis and bowel perforation. The mechanism that leads to mucosal damage remains unclear. However, it is believed that sorbitol, commonly given to counteract PSP's tendency to cause constipation, may play an important role in the development of gastrointestinal injury. Other potential risk factors are uraemia or end-stage renal disease, hemodynamic instability, solid organ transplantation, postoperative status and concomitant opioid administration. The authors present a case of diarrhoea and haematochezia after the administration of PSP without sorbitol, in a patient with hyperkalaemia due to acute kidney injury, in the absence of other risk factors. A colonoscopy was performed and revealed a rectal ulcer which histological findings were suggestive of mucosal injury due to Kayexalate deposition. This case supports the concept that this widely used drug can itself, without sorbitol, cause injury to the gastrointestinal wall. Even though this is a rare adverse effect, the widespread use of this medication may put a large population at risk.

Langerhans cell histiocytosis (LCH) is a rare disease of unknown origin with a heterogeneous clinical presentation, varying from benign and self-limited to lethal. It is classified as single or multisystemic, according to the number of organs involved (one or at least two, respectively). Diagnosis can be challenging and is based on the histological and immunophenotypic examination of affected tissues. Secondary haemophagocytic lymphohistiocytosis is rarely reported in association with LCH and may impair its diagnosis. Some authors suggest that the coexistence of the two disorders is more than coincidental. We present a case of multisystem LCH in a 5-month-old infant, with all risk organs involved, in which severity and rapid progression reflect an association with haemophagocytic syndrome., (2014 BMJ Publishing Group Ltd.)