The most common form of acne, acne vulgaris, is not associated with musculoskeletal abnormalities. Most patients are young males and nearly all are HLA-B27 negative. Acne fulminans often presents with systemic features such as fever and weight loss. Patients with acne conglobata are more likely to have peripheral and axial arthritis, while those with acne fulminans are more likely to have multiple, painful hyperstotic bone lesions. The peripheral arthritis is usually symmetrical, and most commonly involves the ankles and small joints of the feet.
Axial involvement is manifested by sacroiliitis and spondylitis.
Syndesmophytes and coarse paravertebral ossifications are seen, as well as ossification of tendinous insertions, similar to the findings seen in classic seronegative spondyloarthropathies. Biopsies typically show chronic inflammation and fibrosis without evidence for infection. Patients may have elevated serum alkaline phosphatase levels. The cause of this syndrome remains unclear. Exhaustive investigations to identify a nidus of infection have generally been unrevealing, although there are sporadic reports of propionibacterium from bone cultures in these patients.