Pathology of relapsing polychondritis
- Clement J Michet, MD
Clement J Michet, MD
- Associate Professor of Medicine
- Mayo Clinic
Relapsing polychondritis (RPC) is characterized by widespread, potentially destructive, inflammatory, and degenerative lesions. Ear cartilage is classically affected, but RPC may involve cartilage and biochemically and immunologically related connective tissue structures throughout the body (table 1). (See "Clinical manifestations of relapsing polychondritis".)
This topic will review the pathologic changes associated with RPC. The pathogenesis of this disorder is discussed separately. (See "Etiology and pathogenesis of relapsing polychondritis".)
HISTOLOGY OF A TYPICAL ACTIVE EAR LESION
Biopsy of an active ear lesion is representative of pathologic changes occurring at connective tissue sites elsewhere. There is a characteristic spectrum of changes that depends upon the time the biopsy is performed.
●A pleomorphic perichondral infiltrate of lymphocytes with a variable proportion of polymorphonuclear cells, monocyte/macrophages, and plasma cells is initially observed at the chondro-dermal junction (picture 1). Lymphocytes dominate with CD4 helper T cells exceeding CD8 cytotoxic T cells . Contiguous regions of cartilage show evidence of proteoglycan depletion. Coarse granular deposits consisting primarily of immunoglobulin G (IgG) and C3 can be localized by direct immunofluorescence at the junctional site.
●As the disease progresses, the integrity of cartilage is disrupted by invading granulation tissue, which tends to sequester islands of degenerating chondrocytes and depleted matrix (picture 2). IgG and C3 may be seen throughout the matrix. Matrix metalloproteinases (MMP) are expressed in both the perichondral granulation tissue and chondrocytes . Chondrocyte apoptosis is increased in chondritis lesions and correlates with the expression of MMP-3 and cathepsin-K. Nitric oxide expression is increased, reflecting the chondrocyte production of pro-apoptotic MMPs.
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