Pelger-Huet anomaly

Pelger-Huet anomaly is a blood laminopathy associated with the lamin B receptor.

It is characterized by a white blood cell type known as a neutrophil whose nucleus is hyposegmented. It is a genetic disorder with an autosomal dominant inheritance pattern. Heterozygotes are clinically normal, although their neutrophils may be mistaken for immature cells which may cause mistreatment in a clinical setting. Homozygotes tend to have neutrophils with rounded nuclei that do have some functional problems.

Congenital Pelger-Huet anomaly
Is a benign dominantly inherited defect of terminal neutrophil differentiation secondary to mutations in the lamin B receptor (LBR) gene. The characteristic leukocyte appearance was first reported in 1928 by Pelger, a Dutch hematologist, who described leukocytes with dumbbell-shaped bilobed nuclei, a reduced number of nuclear segments, and coarse clumping of the nuclear chromatin. In 1931 Huet, a pediatrician, identified it as an inherited disorder.

It is a genetic disorder with an autosomal dominant inheritance pattern. Heterozygotes are clinically normal, although their neutrophils may be mistaken for immature cells, which may cause mistreatment in a clinical setting. Homozygotes tend to have neutrophils with rounded nuclei that do have some functional problems. Homozygous individuals inconsistently have skeletal anomalies such as post-axial polydactyly, short metacarpals, short upper limbs, short stature, or hyperkyphosis. Identifying Pelger-Huët anomaly (PHA)is important to differentiate from bandemia with a left-shifted peripheral blood smear and neutrophilic band forms and from an increase in young neutrophilic forms that can be observed in association with infection.

Acquired or Pseudo-Pelger-Huet anomaly
Develops in the course of acute or chronic myelogenous leukemia and in myelodysplastic syndromes. In patients with these conditions, the pseudo–Pelger-Huët cells tend to appear late in the disease and often appear after considerable chemotherapy has been administered. The morphologic changes have also been described in myxedema associated with panhypopituitarism, vitamin B-12 and folate deficiency, multiple myeloma, enteroviral infections, malaria, muscular dystrophy, leukemoid reactions secondary to metastases to the bone marrow, and drug sensitivity, sulfa and valproate toxicities are examples. In some of these conditions, especially the drug-induced cases, identifying the change as Pelger-Huet anomaly is important because it obviates the need for further unnecessary testing for cancer. Peripheral blood smear shows a predominance of neutrophils with bilobed nuclei which are composed of two nuclear masses connected with a thin filament of chromatin. It resembles the pince-nez glasses, so it is often referred to as pince-nez appearance. Usually the congenital form is not associated with thrombocytopenia and leukopenia, so if these features are present more detailed search for myelodysplasia is warranted, as pseudo-pelger-Huet anomaly can be an early feature of myelodysplasia.