AGES OF ONSET: PEDIATRIC V.S. ADULT ONSET
Pediatric onset scleroderma is defined as cases of scleroderma in which the patient is less than 18 years old when symptoms begin.
Localized scleroderma (LS) is the more common type in children.
Systemic scleroderma (SSc), the type of scleroderma that also affects the internal organs, is the more common type of scleroderma in adults. However, in children, LS is around 10 times as common as SSc. Juvenile localized scleroderma (jLS) affects 50 per 100,000 children – a prevalence similar to that of juvenile diabetes mellitus. The estimated prevalence of juvenile systemic scleroderma (jSSc) is 2 per 100,000.
The average age of onset of jLS is 6-8 years old, while the average age of onset of jSSc is 8-11 years old.
Localized and systemic scleroderma are distinct. It is extremely rare for both to occur together (<0.1%). When this does happen, they typically have a similar time of onset. One does not develop into the other.
Although each child’s case is different, there are general patterns of outcome and prognosis.
These patterns are different from those of adult onset scleroderma.
Pediatric onset and adult onset scleroderma have the same subtypes of localized scleroderma, but with different prevalences.
LS subtypes include linear scleroderma (trunk/limb, head), circumscribed morphea (superficial or deep), mixed morphea, and generalized morphea. In children, mixed morphea and linear scleroderma of the trunk/limb and head are much more frequent.
Certain extracutaneous (non-skin) involvements are more common in children.
This is due to the increased frequency of deeper tissue involvement in jLS linear subtypes. Such extracutaneous involvement includes joint contracture, limb length differences (affected limb is shorter), and limb girth differences (affected limb has a smaller girth). If linear head involvement is present, skull changes, linear band on the scalp, mandible/maxilla (jaw) changes, brain lesions/changes, or neurological symptoms may occur.
The duration of localized scleroderma is longer in children than in adults.
Cohort studies on adults generated the thought that LS would “burn out” after 3-5 years. However, more recent cohort studies have shown that this does not apply to jLS. In jLS, disease duration can range from 7 to 10+ years. For example, a recent European cohort demonstrated that 12.5% of jLS patients still had active diseases after 10 years. (Marini, Zulian Autoimmunity Reviews 17 (2018) 727-734) With a longer disease duration in jLS, there is a higher risk for sequela of (lasting damage to) the underlying tissue if it is left untreated.
With pediatric onset localized scleroderma, it is more likely that the disease will affect limb and face development/growth.
This is not as much of an issue in the adult-onset disease because adults have already fully matured.
Although extremely rare, children get systemic scleroderma (SSc) as well.
Compared to adult-onset, the rate of internal organ involvement is typically less. Thus, the prognosis is more favorable. This trend in severity is opposite of the differences observed in localized scleroderma. However, systemic scleroderma affects each child differently and can be extremely severe. Juvenile systemic sclerosis differs from the adult-onset disease. The diffuse subtype dominates, and the disease often presents insidiously.
Dropping percentiles on growth charts occurs in the pediatric onset disease.
If the child has gut involvement, they may not get the nutrition required for growth. The resulting failure to gain weight will be reflected by a deceleration on the child’s growth chart.
Much less information on late-age onset scleroderma is available.
It has been suggested that older systemic scleroderma patients are at a greater risk for pulmonary hypertension, renal impairment, cardiac disease, and muscle weakness. It has also been suggested that late-age onset is protective against digital ischemia (reduced blood flow), with lower prevalences/severities of Raynaud’s Phenomenon and digital ulcers. These differences and the reasons for them have not been thoroughly studied or confirmed.
However, awareness of the distinct risk for specific organ involvement in SSc, especially pulmonary hypertension, should guide the care of elderly SSc patients.