Cyclic Neutropenia Mimicking Crohn's Disease: Two Case Reports and a Narrative Review

: Cyclic neutropenia is a rare hematological condition characterized by periodic fluctuations in neutrophil counts, with a 21-day periodicity. Clinical presentation varies from mild to severe forms of the disease, with the onset of recurrent fever, painful oral ulcers, recurrent bacterial infections, peritonitis, and septic shock. The availability of granulocyte colony-stimulating factor (G-CSF) has revolutionized the management and natural history of this disease, regulating the proliferation, differentiation, and maturation of the progenitor cells, and reducing the duration of neutropenia. Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is a group of chronic pathologies that affect the gastrointestinal tract. The onset of both diseases may be at a young age (even during childhood or adolescence), and clinical manifestations may lead to misdiagnosis, due to similar characteristics such as recurrent infections, oral ulcers, perianal abscesses, and infertility. Moreover, the two pathologies are rarely associated, with different management and therapeutic options. Here, we describe two case reports of patients who underwent surgery because of diagnosis of complicated CD. After surgery, due to persistent neutropenia, the hematologist consultant confirmed suspicions of cyclic neutropenia, and G-CSF therapy was started with benefits, underlining the crucial importance of proper differential diagnosis.