Intranuclear crystalloids associated with abnormal granules in eosinophilic leukocytes.

Ultrastructural evaluation of eosinophilic leukocytes from a 2-yr-old asymptomatic girl with chronic benign neutropenia (CBN) revealed a variety of morphological abnormalities. All eosinophils obtained from blood and marrow specimens contained multipole microcrystalloids in most of the mature cytoplasmic granules. An increase in crystalloid-free, immature granules in late (bilobed nuclei) eosinophils suggested a delay in granule maturation. The eosinophil granules appeared to be of normal size and demonstrated normal acid phosphatase reactivity. Eosinophilic myelocytes contained abnormal cisternae of rough endoplasmic reticulum (RER) and lacked abundant elongated RER cisternae seen in normal cells. A few eosinophilic myelocytes in specimens of bone marrow from the child contained large intranuclear crystalloids measuring up to 3 mu in length. The intranuclear crystalloid contained as cubic lattice of dense material with a periodicity similar to that described for cytoplasmic crystalloids. The ultrastructural morphology of marrow neutrophils was normal, as described in other cases of CBN. Ultrastructural examination of blood eosinophils from the father demonstrated microcrystalloids in cytoplasmic granules identical to those seen in the child. The father was asymptomatic and had normal leukocyte counts. Thus, anomalous crystalloid granule genesis occurred in the father and daughter and was not necessarily associated with neutropenia or clinical symptomatology. This anomaly is associated with the accumulation of intranuclear crystalloid material in eosinophilic myelocytes, which do not appear to be released from the marrow compartment.