Case Report: Early-onset juvenile psoriatic arthritis presenting at 15 months—a diagnostic challenge in infancy

This case describes a rare early-onset presentation in a 15-month-old girl, who first developed guttate psoriatic lesions followed by knee arthritis confirmed by ultrasound. The patient had a strong family history of autoimmune diseases. Immunological testing, including antinuclear antibodies, was negative, but with positive non-specific inflammatory markers, such as C-reactive protein and erythrocyte sedimentation rate, offering a clue about an inflammatory process causing this presentation. The diagnosis of juvenile psoriatic arthritis was made according to the International League of Associations for Rheumatology (ILAR) Criteria for Juvenile Psoriatic Arthritis. This case highlights an uncommon presentation of juvenile psoriatic arthritis in a toddler, characterized by guttate psoriasis preceding arthritis and negative autoimmune serology. Recognition of this pattern and early imaging-confirmed synovitis supported the timely initiation of disease-modifying therapy, resulting in sustained clinical remission.