Juvenile psoriatic arthritis with nail psoriasis in the absence of cutaneous lesions.

A 4-year-old white boy without a significant family history had morning stiffness and painful swelling of his left knee and ankle, right elbow, and dorsolumbar region of 2 months’ evolution. The following laboratory studies were within normal limits: complete blood cell count, C-reactive protein (CRP), latex, antistreptolysin, and antinuclear antibodies. Rheumatoid factor was negative and an increase in the erythrocyte sedimentation rate (ESR) was detected (56 mm/h). The pediatric department made an initial diagnosis of juvenile rheumatoid arthritis, and treatment with acetylsalicylic acid at 100 mg/kg/day and naproxen at 10 mg/kg/day was started. A thick, yellowish toenail was diagnosed as onychomycosis. No mycologic investigations were performed. Intermittent episodes of painful arthritis of different joints were present. The radiographic features of the peripheral joints included: narrow joint spaces, articular erosions, soft tissue swelling, and diffuse bony demineralization. Characteristic bilateral sacroiliitis and a swollen tendon sheath on the left ankle were detected. At 11 years of age the nail changes had extended to five other toenails and to four fingernails, were yellow–brown in color, and showed marked subungual hyperkeratosis ( Figs 1, 2). The rest of the nails showed significant nail pitting. Trials of griseofulvin alternated with itraconazole in an irregular form for five consecutive years resulted in no clinical improvement, which prompted a consultation to our dermatology department. On three different occasions, KOH nail specimens were negative for fungus, but the presence of parakeratotic cells aroused the suspicion of psoriasis. A complete physical examination was negative for psoriatic skin lesions. A nail bed biopsy specimen was characteristic of nail psoriasis ( Fig. 3). Figure 1. Thickened nails with severe subungual hyperkeratosis in five fingernails Figure 2. Secondary deformity of nail plate. No “sausage” fingers were observed Figure 3. Light microscopic appearance of a nail biopsy specimen showing parakeratotic hyperkeratosis, elongation of interpapillary processes, and Munroe abscess (arrow) (hematoxylin and eosin stain, ×40) The following human leukocyte antigens (HLAs) were positive: A9, A10, B12, B27, Cw1, Bw4, DR6, DR7, DQ1, DQ2, and DR53. A diagnosis of juvenile psoriatic arthritis associated with nail psoriasis was made. Toenail involvement became so painful that walking became very difficult. Occlusive 40% urea in vaseline applied to the affected toenails for 48 h resulted in significant improvement. Currently, the patient is 20 years old with nail involvement, but no psoriatic skin lesions have ever been observed.