A 24-year-old male patient without a personal or family history of psoriasis visited our department because of a 13-year history of recurrent redness, swelling, pustules and tenderness on the tips of several digits on both the hands. Pustules were initially found around the nails, followed by scales and crusts, leading to onychodystrophy and progressive deterioration of the nails. Four years ago, he suffered unbearable burning pain in the fingers, which seriously affected his sleep quality, and white exudate appeared when the hands dropped, accompanied by swelling. Two years ago, the right forearm was sprained, and one day later, a large edematous cutaneous lesion with erythema appeared on the dorsum of the forearm from the wrist to the elbow. The local dermatologist diagnosed it as erysipelas, and the patient was treated with intravenous flucloxacillin (500 mg, four times per day). The erythema highly subsided after 15 days; however, the pustules persisted on the forearm, and the lesions recurred thereafter.
Dermatologic examination revealed severe erythema with clear boundaries on all tips of the digits of his right hand and the thumb, ring finger, and little finger of his left hand, with several erosions and covered with a thick yellow crust. A similar skin lesion measuring 2.5x2 cm in size was seen on the right forearm. Further examination revealed that anonychia occurred on five fingers, three fingernails were dystrophic, and seven fingers could not be fully extended (Figure 1A-C). The patient reported a pain score of 8 out of 10 on the visual analog scale (VAS) pain scale and 24 points out of 30 on the Dermatology Life Quality Index (DLQI). According to the clinical manifestations, the patient was diagnosed with ACH. 
During the first 9 years of the disease course, he was treated at several hospitals with multiple oral and topical medications, with little or no response. Four years ago, he was admitted to a tertiary hospital in Beijing, where topical medications and systemic traditional Chinese medicine were prescribed, but without any success. He was later treated with acitretin (20-30 mg/day for 3 years) and narrow-band ultraviolet B phototherapy (84 sessions). Although these drugs did not cause apparent side effects, the lesions remained unaffected and worsened.
Laboratory tests and imaging examinations were conducted, including blood and urine tests, testing of the liver function, kidney function, hepatitis B and hepatitis C antibodies, the interferon-gamma release assay (IGRA), chest computed tomography (CT) as well as anteroposterior and oblique position X-rays for the hands. The X-rays of both the hands showed no bony abnormalities, but the swelling of the surrounding soft tissue with uneven density and edges at the distal phalanx of all fingers of the right hand, and the thumb, ring finger, and little finger of the left hand. The IGRA test showed that the tuberculosis T cells (T-N) were at a level of 172.8 pg/mL, indicating that the T-cell test for tuberculosis infection was positive. Chest CT showed localized areas of thickening, adhesions, and calcifications in the pleura on the right side. Active tuberculosis was excluded after a visit to the local chest hospital. No other abnormalities were found.
On March 21, 2022, we first administered the patient the recommended dose of 45 mg of Ustekinumab to the patient, followed by a second injection of 45 mg 4 weeks later, and the subsequent two injections were given in the intervals of 12 weeks. So far, the patient has received four injections. There were no adverse effects during the treatment. The pain was completely eliminated half a month after the first injection, and improvement in the skin lesions was observed 4 weeks after the treatment, and the skin lesions were almost completely resolved after the third treatment (28 weeks after the initiation of the treatment) (Figure 1D-F; for details of the timeline, see Figure 2). We observed progressive improvement in DLQI from the first to the fourth injection, with the scores of 27, 23, 14, and 2 points, respectively. We noted a considerable improvement in the nails before the third injection (16 weeks after the initiation of the treatment). During a telephone-based follow-up 20 days after the fourth injection, the patient reported that new pustules occasionally appeared, but they quickly crusted and healed, having no adverse effect on daily life.