Paediatricsmiddle twist
A 7-week-old girl is brought in because she cries inconsolably for four to five hours each evening, drawing her legs up, and has done so since three weeks of age. She is exclusively breastfed. Her weight has fallen from the 50th to the 10th centile, she has passed streaks of blood and mucus in loose stools twice this week, and she has dry, itchy patches behind her knees. She is afebrile, the abdomen is soft and the nappy area is normal. Which one of the following single conditions explains all of her features?