Acute Thymic Involution
Jessica M. Comstock, MD
Key Facts
Terminology
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Incidental thymic involution caused by endogenous steroid release in response to various stressful situations
Etiology/Pathogenesis
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Numerous stressors including infection, chronic disease, malnutrition, and corticosteroid use
Microscopic Pathology
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Grade correlates with duration and severity of illness
Top Differential Diagnoses
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Thymic dysplasia
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Physiologic involution
This thymus at low power shows the classic “starry sky” appearance of acute thymic involution. The dense blue cortex (the sky) is punctuated by macrophages (the stars). |
The “starry sky” appearance of acute thymic involution is caused by macrophages ingesting lymphocytes (lymphophagocytosis  ). This process is caused by endogenous steroid release due to stress. |
TERMINOLOGY
Synonyms
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Thymic atrophy
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Acquired hypoplasia
Definitions
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Incidental thymic involution caused by endogenous steroid release in response to various stressful situations
ETIOLOGY/PATHOGENESIS
Environmental Exposure
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Malnutrition
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Prolonged physical or emotional stress
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Chronic disease
Infectious Agents
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Viral infections, especially HIV
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Bacterial infections
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Fungal infections
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Chorioamnionitis
Treatment Related
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Acute and chronic GVHD
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Chemotherapy
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Irradiation
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Prolonged treatment with corticosteroids
CLINICAL ISSUES
Epidemiology
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Age
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All ages, including fetal
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