Clinical parameters of patients with Duffy null phenotype: a single centre, retrospective review.

We characterise the clinical parameters of patients referred for isolated neutropenia who were found to express the Duffy null phenotype and subsequent diagnosis of Duffy null associated neutrophil count (DANC). This is a single-centre, retrospective review of adult patients (18 years and over) who were referred to a tertiary hospital for further investigation of isolated neutropenia between June 2023 and February 2024. Patient demographics, co-morbidities, ethnicity, medications, laboratory results and final diagnosis were obtained from electronic database and chart reviews. Data were collated and analysed using descriptive statistics. A total of 34 patients (35.3% male) were identified, with a median age of 43 years (IQR 31, 61). The median absolute neutrophil count was 1.42×10/L (IQR 0.74, 1.80). Ten patients (29.4%) referred for isolated neutropenia were subsequently found to have another cytopenia. Ten patients (29.4%) had confirmed Duffy null status, with all 10 patients reporting African heritage. Of those with confirmed Duffy null status, there was no history of recurrent infections, constitutional symptoms or other causes of isolated neutropenia. Of those who expressed Duffy positive phenotype (n=24), three patients (12.5%) were found to have a causative haematological disorder. Other causes of neutropenia in the cohort included autoimmune (20.6%), cyclical (5.9%) and drug-related (5.9%). Ten patients (29.4%) had no cause identified or had spontaneous resolution of their neutropenia. DANC was the most common cause of referred isolated neutropenia. Initial investigations could be limited to assessing Duffy null status in asymptomatic patients from African heritage.