Acute thymus involution in infancy and childhood: a reliable marker for duration of acute illness.

To evaluate the relationship between histologic parameters and clinical data, we studied thymus histology in 234 fetuses and young children who died after a short period of acute illness. Thymus weight and volume percentages of interstitium, cortex, and medulla were significantly related to prenatal or postnatal status and age of the patient. Thymus weight was related to the duration of acute illness only in prenatal patients. The histology, categorized in five grades according to appearance of macrophages (with a starry-sky aspect) in the cortex, increase of interlobular interstitium, and lymphodepletion of the cortex, correlated significantly with the duration of acute illness and not with any other clinical parameter. This finding enables the pathologist to estimate the duration of acute disease before death.