Psoriasis is one of the most common childhood skin disorders, the second after atopic dermatitis. Psoriatic Arthritis (PsA) is a chronic inflammatory disorder of the joints, spine and enthesis, usually associated with psoriasis. In children, PsA belongs to the group of juvenile idiopathic arthritis (according to the classification of the International League of Associations for Rheumatology, ILAR). The paper reviews the current scientific literature data on PsA peculiarities in childhood, the highest incidence in children, distribution by gender, as well as the predominant forms of joint syndrome.
Results: Juvenile PsA is characterized by the pronounced clinical heterogeneity. The disease is twice as common in the girls. Two peaks of incidence are distinguished among 6-7 years and 14-18 years. Skin events precede the development of arthritis in 30% of children. The predominant form of the disease in children is asymmetric oligoarthritis.
Juvenile; Oligoarthritis; Onychodystrophy; Psoriasis; Psoriatic arthritis
Psoriasis is diagnosed annually in about 20 thousand children under the age of 10. Up to 30% of adults fell ill with psoriasis under 18 years old and up to 70% of them had a burdened family history while the burdened history was revealed only in 30% of those who were affected in their adulthood. Twohighest incidences of psoriasis are currentlydetectedamong 6-7 years old and 14-18 years old children. It isbelieved that a feature of psoriasis in childrenis a tendency to the more pronounced exudative phenomena and involvement of joints and enthesis which is more rare than in adults. This paper studied the features of the course and clinical picture of psoriatic arthritis in childhood and adolescence.
Study the features of epidemiology, clinical course and articular syndrome in PsA in children
In this paper we examined the scientific literature for the period of 2010-2020 dedicated to the clinical features of psoriatic arthritis in children. Literature sources published earlier than 2010 were not used in the review.
The highest incidence of PsA in children falls on the senior preschool age (6-7 years) and puberty (14-18 years) and thuscoincides with the peak of the incidence of psoriasis . To diagnose PsA in children is often difficult due to the peculiarities of the disease - differences in the clinical course, localization and form of the articular syndrome. Among juvenile arthritis PsA accounts for up to 10%, there is a pronounced clinical heterogeneity of the disease, as well as gender differences - girls account for 60-70% of sick children . Data on the frequency of occurrence of PsA in childhood varies. According to the American register Childhood Arthritis and Rheumatology Research Alliance (2017), PsA is recorded in 5% of children with juvenile arthritis, however, according to the German register Biologics in Paediatric Rheumatology (2016), the proportion of PsA among juvenile idiopathic arthritis is 7.4% [2,3]. According to Russian data, PsA accounts for 1.5% of all juvenile idiopathic arthritis (Union of Pediatricians of Russia, 2017), according to the I.M. IM Sechenov, this pathology occurs in 6% of children with juvenile idiopathic arthritis . When diagnosing juvenile PsA they usually rely on the Vancouver diagnostic criteria (1989). According to these criteria, juvenile PsA is exhibited in the presence of arthritis and typical psoriatic rash or arthritis and at least 3 of the follow "minor" signs: psoriasis-like rash, dactylitis, onychodystrophy, psoriasis in relatives of the 1st or 2nd degree of relationship. Probable juvenile PsA is diagnosed if arthritis and at least 2 of the "minor" signs are present .
The average age of PsAincidence among children is 6.2 years, the minimum and maximum ages of the disease onset were 4 months and 15 years, respectively . In more than half (71%) of children PsA was preceded by skin psoriasis (skin syndrome appeared inaverage 5 years), in 29% of cases the disease began with skin psoriasis (joint involvement occurred in average 2.5 years) . It was noted that the disease often remains undetected even in the presence of characteristic symptoms due to the clinical features of psoriasis in childhood, thus the connection between PsA and skin psoriasis also remains undetected, especially in cases where the lesion of the musculoskeletal system begins with mono- or oligoarthritis joints of the hands observed in 35-40% of cases . Asymmetric oligoarthritis in 40-80% of children further spreads to other joints (knee, elbow, etc.) . The predominant forms of skin psoriasis were also revealed in children with PsA - in 76.3% of children plaque psoriasis was revealed, among which 39% were found to involve the scalp, 13% of patients had teardrop-shaped psoriasis, the palmar-plantar form was found in 5.1% of cases. In 22% of children, skin syndrome was combined with onychodystrophy. Isolated psoriatic onychodystrophy occurred in 5.1% of cases. Clinical forms of onychodystrophy were dominated by onycholysis (35%), “oil stain” symptom (21%), “thimble” symptom (18%) .
Currently a gradual onset of juvenile PsA is one of the main clinical features. The first symptoms of PsA in children may be: weight loss, increased fatigue, myalgia. In about 30% of children at the onset of the disease were noted morning stiffness in the joints, edema and sharp paroxysmal pain most intense in the morning hours . In most children (up to 80%), psoriatic arthritis is manifested by the involvement of the proximal and distal interphalangeal joints of the hands and feet, the metacarpophalangeal, metatarsophalangeal joints, as well as the knee and shoulder joints. At the onset of the diseasetwo thirds of patients (68.7%) have mono- and oligoarticular forms of articular syndrome, the process most often begins with damage to the proximal interphalangeal joints of the hands, ankle and knee joints. As for the rheumatoid-like form of articular syndrome (polyarthritis), at an early stage it occurs less frequently (18% of children), psoriatic spondylitis is found in 13.2% of patients .
The features of the articular syndrome in children with PsA are still being studied in detail. It is believed that in juvenile PsA any joints, up to the temporomandibular joints, can be affected, however the knee joints, small joints of the hands and feet, as well as ankle joints are most often involved in the process - in 41%, 29% and 31% of cases, respectively. With regard to the classification of PsA, they successfully keep to the classification used for adults, according to which 5 forms of the disease are distinguished: asymmetric oligoarthritis (35-40%), arthritis of the distal interphalangeal joints (DMFS arthritis) (15-29%), mutilating arthritis, psoriatic spondylitis. Axial arthritis is characteristic - damage to all joints of one finger is developing as a rule afterdactylitis. Cyanotic skin discoloration and sausage-like appearance of the finger are often observed in combination with tendovaginitis of the flexor tendons of the fingers . Isolated arthritis of the distal interphalangeal joints in children is extremely rare - more often it is combined with damage to the peripheral joints and psoriatic onychodystrophy. In 5% of children, symmetric lesions of the metacarpophalangeal and proximal interphalangeal joints of the hands are observed, which is the most important in the onset of the disease (in the absence of skin syndrome)as this option is easily mistaken for a seronegative polyarthricular variant of juvenile idiopathic arthritis. Mutating arthritis in PsA is manifested as a rule by osteolysis of the phalanges of the fingers and toes, due to the shortening of the fingers their characteristic deformation develops. It often takes years for this form of the disease to develop, and it is generally rare in childhood and adolescence. Psoriatic spondylitis in children in isolated form occurs in 13% of cases. By its severity, this form of articular syndrome can be compared with juvenile spondyloarthritis . Changes in the articular syndrome were also identified over time: on average5 years after the onset of the disease rheumatoid-like form of PsA begins to prevail (41% of patients), the proportion of asymmetric oligoarthritis gradually decreases (24.1%), the frequency of spondyloarthritis (24%) and mutating arthritis increases (11%) .
The clinical picture of PsA in children is extremely heterogeneous and has its own characteristics. Among children with this disease the girls are twice as common as the boys. There are two PsA high incidences in childhood and adolescence - 6-7 years old and 14-18 years old, and the second peak is more pronounced. In 30% of childrenskin conditions precede the development of arthritis. At the onset of the disease the majority of patients have asymmetric oligoarthritis followed by a gradual increase in the proportion of polyarthritis. Further study of the characteristics of PsA in children and adolescents will make it possible to develop more effective measures for the timely diagnosis of this disease.