An ache, a swollen joint, a limp, or a new rash on your child's body can be a sign that he or she has juvenile arthritis — a chronic disease that affects children as young as six months old. Approximately 294,000 children under the age of 18 in the United States have arthritis or other rheumatic conditions, reports the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). The autoimmune disease, which releases chemicals that can damage healthy tissues and as a result cause inflammation and pain, is diagnosed if a child is younger than 16 and has experienced swelling in one or more joints for at least six weeks. The most common type of juvenile arthritis is juvenile idiopathic arthritis, also known as juvenile rheumatoid arthritis, because the condition has not been linked to a direct cause. While the childhood disease affects both boys and girls, young Caucasian girls appear to be more susceptible to oligoarthritis and polyarthritis, says Cleveland Clinic. Both adolescent groups are usually diagnosed with the chronic condition between the ages of two and 16.

The cause of juvenile arthritis has yet to be defined by scientists but current research leads to the possibility of it being a genetic predisposition — genes a child receives from family members that may cause the development of the disease in combination with other factors. In a study published in Nature Genetics, an international research team examined 2,816 cases of juvenile arthritis from more than 40 pediatric rheumatology clinics to see what genes were linked to the childhood disease. The results of the study showed that there were 14 new genes that were directly linked to juvenile arthritis — aside from the original three identified prior to the study. "These findings will help us understand how the long suspected genetic contributions to JIA are driving the disease process, with the ultimate goal being earlier and improved diagnosis and treatment," said Susan Thompson, lead author of the study and researcher in the division of rheumatology at Cincinnati Children's Hospital Medical Center.

Genetics alone are not solely responsible for the development of the childhood disease. The condition is considered to be multifactorial, which affirms that there are other factors that influence the health problem, says John Hopkins medicine. Environmental factors in combination with genes can trigger juvenile arthritis in children. Research on environmental determinants for juvenile arthritis is limited but has indicated that the several risk factors below can accelerate the condition.

Lack of Breastfeeding

A mother's milk can be a source of prevention for juvenile arthritis. Human breast milk influences a child's immune system due to the antibodies found in the milk from the mother's body. In a study published in the Journal of Rheumatology, researchers examined whether children with juvenile rheumatoid arthritis were less likely to have been breastfed. Data was obtained from a survey of mothers who had children with arthritis — 54 children were not breastfed and 79 were breastfed. The results of the study showed that children who were breastfed had a 40 percent chance of developing juvenile idiopathic arthritis, compared to their counterparts.

Maternal Smoking

In adult rheumatoid arthritis, smoking and gender are risk factors for developing the disease, says the University of Maryland Medical Center. Researchers decided to apply the same concept and examine the independent and joint effects of maternal smoking in pregnancy and gender in relation to the development of juvenile arthritis and other types of arthritis in the first seven years of life. In the study published in the International Journal of Epidemiology, researchers observed 58,841 singleton births from the Finnish Medical birth Registry, which provided information on whether or not the mother smokes and the exposure of cigarettes per day. The results of the study showed that tobacco smoke increased the risk of juvenile rheumatoid arthritis and other types of arthritis in girls, but not in boys.

Childhood Infections

The role of infection as an environmental determinant of juvenile arthritis has been reviewed by many scientists. The notion that infections can prompt the childhood disease in children was a concept studied by researchers in the University of Istanbul in Istanbul, Turkey. In the study published in Journal of Paediatrics and Child Health, researchers evaluated the presence of parvovirus B19 — a virus that causes a distinctive bright red rash on a child's cheek, and is often referred to as slapped cheek syndrome — in children who presented acute arthropathy. Seventy-five children with parovirus B19 were a part of the study, along with 75 healthy children. The results of the study showed that the children with the virus who had arthropathy were more likely to develop juvenile arthritis compared to their counterparts. Parovirus B19 may thus be a predictor of the onset of the childhood disease.

Parents' Socio-Economic Status And Siblings

The socioeconomic status of a child's parents and the presence of siblings can be environmental risk factors for juvenile arthritis. In a study published in the Journal of Rheumatology, researchers examined the socioeconomic background of children with juvenile arthritis in Denmark. The socioeconomic status of the children's families was examined prior to the onset of the disease from the Fertility Database of Statistics Denmark with a reported 220 cases of the childhood disease. The results of the study unveiled that there were three socioeconomic factors that were independent variables associated with the risk of developing juvenile arthritis within the following year. An only child has a risk of developing the disease 1.6 times more compared to a child with siblings, children who had parents with a high income had 1.9 times the risk than children from low-income families, and children who lived in an urban city had 2.7 times the risk than children who lived on a farm. The results of this study may be related to the hygiene hypothesis.