Primary care physicians play a crucial role in diagnosing and managing rare eosinophilic diseases: HES and EGPA.

Hypereosinophilic syndrome (HES) and eosinophilic granulomatosis with polyangiitis (EGPA) are chronic eosinophilic diseases with serious multisystem manifestations. Patients with HES or EGPA often fail to receive a timely diagnosis, and while these conditions are considered rare, frequent under-recognition indicates that their true prevalence likely exceeds current estimates. Increased primary care physician (PCP) awareness of these systemic eosinophilic conditions and the "red flags" that should trigger referral will help more patients receive timely diagnosis and care. Patients with HES or EGPA present with a heterogeneous range of symptoms and manifestations that can overlap with other conditions, making diagnosis challenging. PCPs should be aware that the following are red flags that warrant further investigation and trigger expert referral: blood eosinophil count ≥10% of total peripheral white blood cells or ≥1,000 cells/μL; persistent hypereosinophilia, noting that systemic corticosteroid treatment may variably impact the degree of eosinophilia; refractory asthma symptoms with the need for prolonged or recurrent systemic corticosteroid treatment; reports of decreasing efficacy to asthma therapy; extra-pulmonary findings in the setting of eosinophilia; multiorgan system involvement; and evolving or worsening signs and symptoms over periods of weeks to months or years. PCPs play a key role in the diagnosis and management of rare eosinophilic diseases. By being aware of HES and EGPA and their associated red flags, PCPs are well-placed to recognize these conditions early, trigger further investigations, and coordinate effective multidisciplinary care. This can help patients receive a more accurate diagnosis on time and faster access to treatment, which may ultimately improve patient outcomes.