We describe the presentation and course of CD in early- (age 0–5 yr) versus later (age 6–17 yr)-onset disease in the pediatric population. As expected, the average length of follow-up was longer in age 0–5 yr group compared to the age 6–17 yr group because of transition to adult care as the children get older. However, the statistical analyses account for the total length of follow-up.
Clinical data on the early-onset group are sparse because this age group represents a smaller proportion of the pediatric IBD population. Sawczenko and Sandhu (15
) reported on 739 incident IBD cases of age less than 16 yr diagnosed between June 1, 1998 and June 30, 1999. In total, 431 were classified as CD. Nine CD cases (2.1%) were of age less than 5 yr at diagnosis. Four percent of patients were less than 5 yr of age at diagnosis (N = 503) in Griffiths’ (16
) report on children with CD diagnosed from 1980 to 1999. In our cohort of children with CD, 9.9% of our population was of age 0–5 yr at the time of diagnosis.
The differences in the presentation and course of disease may indicate a unique disease phenotype in the 0–5 yr age group, which may affect our approach to management in this age group. Paul et al
) analyzed data from 413 consecutive pediatric IBD outpatients (1995–2000) and compared children presenting before and after the age of 5 yr (5–15 yr). CD was diagnosed in 254 children, of which 17 patients were diagnosed before the age of 5 yr. In the early-onset group (age less than 5 yr), no children had proximal and ileal disease, 34% had ileocolic disease, and 76% had isolated colonic disease. In contrast, 26% in the later-onset group had proximal and ileal disease, 48% had ileocolic disease, and 26% had isolated colonic disease. The early-onset group showed a predominantly isolated colonic disease distribution, while the children presenting over the age of 5 yr showed a predominantly ileocolic pattern. In our cohort, both age groups had predominantly combined small bowel and colonic disease. A larger proportion of our younger age group had colonic disease without small bowel involvement compared to the older age group. As with our cohort, Paul et al
. found no significant differences in the blood parameters (hemoglobin, albumin, and ESR) between the age groups (17
Sawczenko and Sandhu (15
) reported a significantly greater proportion of children of Asian origin among the children under the age of 5 yr in their cohort of 739 children with IBD. Asian refers to those reported to be of Indian, Pakistani, or Bangladeshi origin in their cohort. In our population of children with CD, we found a larger proportion of the age 0–5 yr group was Asian/Pacific Islander or Hispanic, while a larger proportion of the age 6–17 yr group was African American.
In our cohort of children with a final diagnosis of CD, a higher proportion of the younger age group was initially classified as UC or IC. The younger age group also had a higher proportion of rectal bleeding and colonic disease without small bowel involvement that may explain the initial classification as UC/IC before the ultimate diagnosis of CD was established. The children in the older age group presented with more varied symptoms: abdominal pain, weight loss, or fever were more prevalent in the 6- to 17-yr-olds. Although the higher prevalence of fever noted in older children did not meet statistical significance (P = 0.07), the point estimate of 2.06 and the range of large HRs consistent with these data (95% CI 0.93–4.55) suggests clinically important results. Furthermore, the older age group was at higher risk for the development of an abscess, a fistula, a stricture, or a perianal fissure. Although the higher risk for the development of a perianal fissure noted in older children did not meet statistical significance (P = 0.06), the point estimate of 2.24 and the range of large HRs consistent with these data (95% CI 0.97–5.19) suggests clinically important results. These differences in the presentation and course of disease suggest a more complicated disease pattern in the 6- to 17-yr-old age group compared to the 0- to 5-yr-old age group. These findings may explain the greater use of 5-ASAs, antibiotics, corticosteroids, 6-MP/azathioprine, methotrexate, and infliximab in children of age 6–17 yr at diagnosis compared to the younger group. The treatment differences may also reflect the differences in the initial diagnosis between the two age groups. The risk for treatment with tacrolimus, cyclosporine, and thalidomide did not differ by age group; this may be because these medications are less commonly used in pediatric CD overall.
Our findings support the hypothesis that the 0–5 yr age group represents a unique disease phenotype. Prospective studies incorporating serial PCDAI at each visit would be helpful to gauge the differences in disease severity by age group not only at the presentation but also over the course of disease. The incorporation of serial Tanner staging and bone age would allow more accurate interpretation of growth patterns at different stages of development. Investigation of bone density by dual energy x-ray absorptiometry (DEXA) scans obtained at diagnosis and serial time points would improve our understanding of the impact of age at diagnosis on the development of osteopenia/osteoporosis. Ideally, the date of symptom onset would be helpful to assess time to diagnosis to determine whether time to diagnosis varies by age group and impacts future course of the disease. However, determination of the date of symptom onset is problematic, especially when the presenting symptoms and signs (e.g., growth delay) are subtle. Future multicenter prospective studies are needed to improve our understanding of the differences in presentation, management, and outcome by age at diagnosis of CD.