6 had NHL; (#) Giant pronormoblast
(Lantern cell) Seen; (##) atypical maculopapular rash over both lower limbs Table II.
The investigators postulated that this finding might be due to viral tolerance that allows cell development past the pronormoblast
stage, although with decreased production overall (3).
The erythroid lineage demonstrated left-shifted maturation with increased numbers of pronormoblasts
and basophilic normoblasts, many of which contained multiple small cytoplasmic vacuoles.
In pure red cell aplasia giant pronormoblasts
in the marrow are considered pathognomonic.
There are characteristic morphological features on the bone marrow biopsy such as red-cell maturation arrest and giant pronormoblasts
, but the bone marrow biopsy is not required for diagnosis.
Bone marrow examination shows normocellularity with findings of profound depletion of erythroid cells, abnormal very large pronormoblasts
and normoblasts exhibiting intranuclear eosinophilic inclusion bodies (Lampion or Lantern cells).
In M6b, 30% or more pronormoblasts
were present, with an insignificant myeloblastic component.
In the process of erythropoiesis, erythroid cells matures from pronormoblasts
, characterised by the loss of nucleus, condensation of chromatin to form coalescent clumps, formation of siderotic clusters, and the cessation of DNA and RNA synthesis, and optimized haemoglobin production.