The hypereosinophilic syndromes: current concepts and treatments

The hypereosinophilic syndromes (HES) encompass a spectrum of diseases that have increased blood eosinophils and tissue damage in common. The clinical manifestations are protean and may involve any organ system, but especially the skin. Our understanding of these diseases has drastically changed over the past 15 years, along with new classifications that characterize patients with marked eosinophilia. One HES variant, myeloproliferative, is actually chronic eosinophilic leukaemia with a unique genetic marker, FIP1L1-PDGFRA . Such patients are well-controlled by administration of the kinase inhibitor, imatinib, and remissions appear durable with continued imatinib therapy. FIP1L1-PDGFRA is expressed in several cell lineages, thus explaining increases in neutrophils and mast cells in HES. The lymphocytic HES variant is associated with T-cell clones producing interleukin-5 (IL-5) and can evolve into lymphoma. While myeloproliferative and lymphocytic HES are well established and permit elimination of the term, idiopathic, to these varieties, most HES patients do not fall into these categories and are classified as complex (using the 2006 Workshop Report). A recent study showed that a monoclonal antibody to IL-5, mepolizumab, reduced glucocorticoid therapy in HES patients who did not possess the FIP1L1-PDGFRA mutation while controlling eosinophilia and preventing recurrence or progression of tissue damage. These advances augur well for continued progress in the understanding and treatment of HES.     

Molecular basis and cellular mechanisms of eosinophilic esophagitis for the clinical practice

Introduction: Eosinophilic esophagitis (EoE) is a chronic, allergen-driven inflammatory esophageal disease characterized by predominantly eosinophilic inflammation leading to esophageal dysfunction. Recent efforts to understand EoE have increased our knowledge of the disease.

Areas covered: Multiple cells, molecules, and genes interplay with early life environmental factors in the pathophysiology of EoE to converge in the esophageal epithelium at the center of disease pathogenesis. Epithelial cells constitute a mayor cytokine source for TSLP and Calpain-14; an impaired epithelial barrier function allowing penetration of food and microbiota-derived antigens is involved in triggering and maintaining inflammation. Eosinophil and mast cell-derived products, including TGFβ, together with IL-1β and TNFα, promote epithelial mesenchymal transition in EoE, contributing to tissue remodeling by synthetizing and depositing extracellular matrix in subepithelial layers. This article aims to provide a state-of-the-art update on the pathophysiology of EoE applied to clinical practice, and latest research and developments with potential interest to improve the diagnosis and treatment of patients with EoE are revised.

Expert commentary: Preliminary approaches have provided promising results toward incorporating minimally invasive methods for patient diagnosis and monitoring in clinical practice. Early diagnosis and optimized therapies will allow for personalized medicine in EoE.     

Recurrent abdominal pain in children: a clinical approach

The term ‘recurrent abdominal pain’, or RAP, refers mainly to the duration of painful period and frequency of pain. The commonly accepted duration is at least three months in the preceding period, and over this three-month period, there are at least three episodes of pain that are severe enough to affect the daily activities of the affected patients. Over the years, with advances in medical technology and better understanding of the pathophysiology of abdominal pain, more and more organic causes have been identified. However, the most common cause of RAP in children is still functional in origin.     

Prostaglandin D2 receptor d‐type prostanoid receptor 2 mediates eosinophil trafficking into the esophagus

Eosinophilic esophagitis is characterized by eosinophil‐predominant inflammation in the esophagus. How eosinophils migrate and infiltrate into the esophagus, however, is less clear. Our previous study demonstrated that mast cell activation led to eosinophil infiltration in the esophagus. Prostaglandin D2 (PGD2) is an important mediator released from activated mast cells. The present study aims to determine whether PGD2 induces eosinophil infiltration into the esophagus via a d ‐type prostanoid receptor 2 (DP2) receptor‐dependent mechanism. Using an in vivo guinea pig model, PGD2, d ‐type prostanoid receptor 1 (DP1) agonist, or DP2 agonist were injected into the esophagus. Esophageal tissues were removed 2 hours after injections and proceeded to either hematoxylin–eosin (HE) staining or immunofluorescent staining of eosinophil major basic protein (MBP) to compare each treatment‐induced eosinophil infiltration in the esophagus. In a separate study, ovalbumin (OVA)‐sensitized guinea pigs were pretreated with either DP2 or DP1 antagonists, followed by inhalation of OVA to induce mast cell activation. Esophageal tissues were then processed for immunofluorescent staining of MBP. PGD2 injection in the esophagus led to an increase of eosinophil infiltration in esophageal epithelium at the injection site as revealed by HE staining. Increased infiltration of eosinophils was further confirmed by the increased presence of MBP‐labeled immunopositive (MBP‐LI) cells in esophageal epithelium. Injection with DP2 agonist 15(R)‐PGD2, but not DP1 agonist BW 245C, mimicked the PGD2‐induced response. In OVA‐sensitized animals, antigen inhalation increased MBP‐LI cells in esophageal epithelium. Pretreatment with DP2 antagonist BAY‐u3405, but not DP1 antagonist BW 868C, inhibited the antigen inhalation‐induced increase of MBP‐LI cells in esophageal epithelium. These data support the hypothesis that PGD2 induces eosinophil trafficking into the esophageal epithelium via a DP2‐mediated pathway, suggesting a role of DP2 antagonist in the prevention of eosinophilic esophagitis.