Etiology of Relapsing Polychondritis
Relapsing polychondritis is an uncommon autoimmune disorder caused by recurrent inflammation and widespread destruction of cartilage and other connective tissues, with immunological mechanisms playing a major role in its pathogenesis 1, 2.
Autoimmune Pathogenesis
The disease fundamentally involves an autoimmune response to cartilage antigens followed by cartilage matrix destruction by proteolytic enzymes 3. The pathologic hallmark is perichondral inflammation leading to cartilaginous fragmentation and destruction with replacement by fibrosis 1.
Immunological Evidence
- HLA-DR4 association: Susceptibility to relapsing polychondritis is significantly associated with HLA-DR4 (p < 0.001), strongly supporting an immunogenetic basis 2
- The extent of organ involvement shows negative association with HLA-DR6 (p < 0.011) 2
- Similarities and overlapping clinical symptoms with other autoimmune diseases (SLE, rheumatoid arthritis) further suggest immunological mechanisms 2
Antibody Responses
While anti-collagen type II and anti-matrilin-1 antibodies have been identified, they are neither sensitive nor specific and cannot be used for diagnostic purposes 3. This indicates the autoimmune response likely involves yet unidentified cartilage antigens 3.
Novel Genetic Discovery: VEXAS Syndrome
A critical recent development is the identification of VEXAS syndrome (Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) in 2020, which connects relapsing polychondritis to a specific genetic etiology 4, 5.
VEXAS-Associated Relapsing Polychondritis
- Somatic mutations in methionine-41 of UBA1 (the major E1 enzyme initiating ubiquitylation) cause VEXAS syndrome 4
- This connects relapsing polychondritis with systemic inflammatory syndromes and hematologic disorders 4
- Screening for UBA1 mutations is essential in male patients over 50 years old presenting with macrocytic anemia, especially with dermatologic/pulmonary manifestations or thromboembolic complications 5
This represents a paradigm shift, as VEXAS syndrome provides the first monogenic cause for a subset of relapsing polychondritis cases.
Associated Conditions
Approximately 30-35% of patients have concomitant autoimmune or inflammatory diseases 5, 2, 3, including:
- Systemic lupus erythematosus
- Rheumatoid arthritis
- Other connective tissue disorders
This high rate of association reinforces the autoimmune nature of the disease and suggests shared immunopathogenic mechanisms.
Clinical Context of Unknown Etiology
Despite these advances, relapsing polychondritis remains a disease of largely unknown etiology 6, 3. The specific triggers for the autoimmune response and the precise cartilage antigens targeted remain unidentified in most cases. The disease exhibits:
- Equal male/female ratio 1
- Mean age at diagnosis of 51 years (range 17-86 years) 1, 2
- Relapsing course in 86% of patients 1
Important Clinical Caveat
The protean clinical presentations—ranging from intermittent auricular chondritis to life-threatening airway collapse—reflect the heterogeneous nature of the underlying autoimmune process 6. The high risk of misdiagnosis stems from this clinical variability and the fact that only one-third of patients present with typical chondritis at disease onset 5, 3.