Presumptive Spontaneous Lysosomal Storage-Like Disease in a Crl:CD1(ICR) Mouse.

A clinically unremarkable 4.5-mo-old female Crl:CD1(ICR) VAF/Elite mouse was euthanized for scheduled sentinel processing. Gross necropsy findings included significant hepatosplenomegaly and visceral lymphadenomegaly, resulting in a preliminary gross diagnosis of lymphoma. Histology revealed florid accumulations of large, 'foamy' macrophages present in the bone marrow, small intestines, and viscera including liver, spleen, lymph nodes, thymus, uterus, and ovaries. The cytoplasm of these cells was abundant, stained pale blue with Wright-Giemsa and was periodic acid-Schiff positive. Given these characteristic gross and histologic findings, a spontaneous lysosomal storage-like disease was diagnosed in this mouse. Cholesterol ester storage disease is likely, because of the visceral involvement with sparing of the CNS, but could not be diagnosed definitively. To our knowledge, this report is the first to describe a case of spontaneous lysosomal storage disease in an outbred mouse of the CD1(ICR) background.