A mature neutrophil with an unsegmented, or unilobular nucleus, is a sign of myeloid dysplasia. These abnormal neutrophils are often seen in patients with myelodysplastic syndrome or after treatment with chemotherapy or immunosuppressants, among others. They can also occur with very severe infections.

Although this form is often seen as a form of pseudo Pelger-Huët, there are some studies that suggest that rather than a nucleus-production defect, there is premature apoptosis. In the literature, the defects are described both as "monolobular," "unilobular," "pseudo-pelger" or "Stodtmeister cells".