Anitschkow cell

**Definition:** Anitschkow cells (named for Russian pathologist Nikolai Anitschkow) are activated macrophages/histiocytes with abundant amphophilic cytoplasm and a nucleus whose chromatin is condensed into a central slender, wavy ribbon. Longitudinal section: "caterpillar cells". Cross-section: "owl-eye" appearance.

**Pathophysiology (rheumatic fever):** - Follows untreated group A beta-hemolytic Streptococcus pyogenes pharyngitis (not skin infection) by about 2-4 weeks. - Type II hypersensitivity through molecular mimicry. Antibodies and T cells against streptococcal M protein cross-react with host antigens (cardiac myosin, laminin, and other proteins in the valves and myocardium). - CD4+ T cells and macrophages are recruited. Activated macrophages transform into Anitschkow cells and may fuse into multinucleated giant cells.

**Aschoff body:** - Granulomatous inflammatory focus composed of Anitschkow cells, occasional multinucleated Aschoff giant cells, lymphocytes (mainly T cells), plasma cells, and central fibrinoid necrosis. - Can occur in any layer of the heart, so rheumatic fever causes **pancarditis**: pericarditis (fibrinous, "bread and butter" appearance, with friction rub), myocarditis (Aschoff bodies are most characteristic here), and endocarditis (valvulitis). - Valvulitis produces small, warty vegetations along the lines of closure (verrucous endocarditis). The mitral valve is most commonly affected, followed by the aortic valve. - Chronic disease causes fibrosis, leaflet thickening and commissural fusion, and "fish-mouth" mitral stenosis. The MacCallum plaque is a subendocardial lesion in the left atrium.

**Clinical (Jones criteria, major):** - **J**oints (migratory polyarthritis) - **♥** Carditis - **N**odules (subcutaneous) - **E**rythema marginatum - **S**ydenham chorea

Minor criteria include fever, arthralgia, and elevated ESR/CRP. Evidence of prior strep infection is required (ASO or anti-DNase B titers, positive throat culture or rapid antigen test).

**Key points for boards:** - Anitschkow cells and Aschoff bodies are pathognomonic of rheumatic heart disease, but the specific cell type (Anitschkow cell) is a modified macrophage, not a lymphocyte. - Aschoff bodies are usually seen in acute or subacute stages. Late disease shows fibrosis. - Treatment: penicillin for the strep infection, anti-inflammatory therapy (NSAIDs/aspirin) for arthritis and carditis, and secondary prophylaxis with penicillin (benzathine penicillin G) to prevent recurrence. - Complications: chronic rheumatic valve disease (mitral stenosis ± regurgitation), atrial fibrillation, left atrial thrombus, and infective endocarditis. - Do not confuse with: Reed-Sternberg cells (Hodgkin lymphoma, "owl-eye" binucleate nuclei with prominent nucleoli), Langhans giant cells (TB granulomas), and Aschoff giant cells.