Dactylitis

Dactylitis results from inflammation involving the flexor tendon sheaths, entheses, joint synovium, and periosteum of an entire digit, producing uniform, fusiform swelling that distinguishes it from isolated joint synovitis. In rheumatologic disease, it is a key feature of psoriatic arthritis (often asymmetric, affecting fingers or toes) and reactive arthritis, and is included in classification criteria (e.g., CASPAR criteria for psoriatic arthritis). The pathophysiology involves enthesitis-driven inflammation spreading along tendon sheaths, with imaging (MRI/ultrasound) showing flexor tenosynovitis as a major contributor. In sickle cell disease, dactylitis (hand-foot syndrome) occurs in infants and young children due to vaso-occlusion of small vessels in the metacarpals/metatarsals causing bone marrow infarction, presenting as painful, swollen hands and feet—often the first manifestation of the disease. Other causes include tuberculosis (tuberculous dactylitis, 'spina ventosa'), sarcoidosis, syphilis, and other spondyloarthropathies like ankylosing spondylitis. Clinically, dactylitis should prompt evaluation for an underlying systemic disease, with history (psoriasis, back pain, sickle cell trait/disease, infectious exposures) guiding workup. Treatment targets the underlying condition—NSAIDs, DMARDs, or biologics (e.g., TNF inhibitors) for spondyloarthropathy; hydration, analgesia, and hydroxyurea for sickle cell disease.