Low plasma levels of the protein pro‐LL‐37 as an early indication of severe disease in patients with chronic neutropenia

Chronic neutropenia comprises several different diseases that vary in degree of severity and management. We analysed the levels of the neutrophil-derived protein pro-LL-37 in plasma of patients with chronic neutropenia to assess whether it could be used to differentiate different categories of chronic neutropenia. All patients with severe congenital neutropenia were pro-LL-37 deficient. This was in contrast to patients with autoimmune or idiopathic neutropenia, who exhibited normal pro-LL-37 levels while patients with cyclic neutropenia displayed an oscillation of pro-LL-37 in plasma. Plasma levels of pro-LL-37 may thus prove useful for differential diagnosis of chronic neutropenia.