If It Bleeds, It Leads
Psoriatic and systemic Juvenile idiopathic arthritis and Adult-onset Still's disease
The old journalistic adage I used in the title can just as easily be applied to autoimmune disease. That is, the more severe and life-threatening the autoimmune symptoms are, the more healthcare and research resources are applied to the patient and the problem. From a healthcare triage perspective this makes sense—limited healthcare resources have to be allocated in some way. Severity and acuity is the classic measure. For chronic autoimmune symptom sufferers, severity triage can be a supremely frustrating aspect of the healthcare system because optimally functioning in your life matters.
The “bleeders” of Juvenile idiopathic arthritis, are the systemic sub-type along with the similar adult version, called Adult-onset Still’s disease. They have multiple organ involvement and can present with, or progress quickly to, life-threatening complications. For this reason, the available research has kept me deep in the weeds of the fascinating knowledge advancements of the past five years for both systemic Juvenile idiopathic arthritis and it’s close relative—or maybe identical, but older, twin—Adult-onset Still’s disease. You can read more specifics about the comparison between the two in my last post, and more generally about Juvenile idiopathic arthritis and Adult-onset Still’s disease in their Diagnosis Description here.
For this post, I turned my attention to the Psoriatic subtype of Juvenile idiopathic arthritis. It’s one out of six sub-types contained within the catchall basket of Juvenile idiopathic arthritis, defined as arthritis of unknown cause occurring in people under the age of 16. Just to illustrate my point about what does, and does not, get research attention, I did a cursory search of PubMed for all articles in the last five years on “psoriatic juvenile arthritis,” which was the naming convention that proved to be the most accurate, yet inclusive, of all the search terms I tried. It yielded 187 results. Compare that to 1,056 hits for “systemic juvenile arthritis.”
I found a 2022 review article of what is known about the psoriatic sub-type of Juvenile idiopathic arthritis to date: “New Insights on Juvenile Psoriatic Arthritis.” Why didn’t I use “Juvenile Psoriatic Arthritis” as my search term to illustrate the point I made in my last paragraph? Because it also returns all results for “Juvenile Idiopathic Arthritis” including the systemic sub-type. It proved to be too expansive. New Insights…also notes a lack of research on the psoriatic sub-type, so I feel somewhat supported in my results comparison.
Psoriatic Juvenile idiopathic arthritis, under the current study classification criteria (currently in the process of revision to make it more evidence-based), accounts for 5% of cases of Juvenile idiopathic arthritis. Small population subset, not life-threatening: less bleeding, less leading. In other words, last on the priority list. Here again, it becomes clear how much study classification criteria matters.
The separation of the psoriatic and enthesitis (inflammation where tendons and ligaments insert into a bone) subtypes is controversial. The psoriatic sub-type is more common in females. The enthesitis sub-type has a male predominance. If adult Psoriatic arthritis classification is used for children, Psoriatic Juvenile idiopathic arthritis can be associated with the common genetic variant, Human Leukocyte Antigen B27, as can enthesitis-related Juvenile idiopathic arthritis. For the pediatric criteria, HLA B27 positivity excludes the diagnosis of Psoriatic Juvenile idiopathic arthritis, even when other hallmarks of the sub-type are present.
Confounding matters is that two age-related peaks of Psoriatic juvenile idiopathic arthritis are described, toddler and adolescent, with different signs and symptoms of disease depending on age of onset. In the adolescent peak, which the authors find comparable to adult classifications of psoriatic arthritis, enthesitis is common, making differentiation from the enthesitis-related sub-type under the current pediatric classification criteria difficult.
If you happen to remember The Leptin Theory of sex predominance in autoimmune disorders—quickly summarized as the divergence between males and females, at adolescence, of hormones secreted from fat tissues, accounting for the sex differences in autoimmune disease prevalence—then you probably know what’s coming next. I am critical of age-based classification systems delineated by the age ranges of pediatrics and adult medicine specialties. They’re not particularly helpful for clarifying autoimmune disease processes. Psoriatic Juvenile idiopathic arthritis, systemic Juvenile idiopathic arthritis, and Adult-onset Still’s disease, illustrate how problematic age-based classification systems have proved to be. I am curious how useful a pre-adolescent category is. Something to keep in mind going forward.
Why it Matters
In five words or less: early diagnosis and effective treatment. Accurate naming and classification of autoimmune disease leads to better research into disease-causing mechanisms, diagnostic criteria and treatment that targets the cause of disease, and not just the control of symptoms. For example, does it matter if symptomatology is wildly different between diseases that share the same sex predominance, genetic variations, environmental exposures and immune system pathologies? Treatment that targets the underlying genetic, environmental and immune causes would be the same, regardless of body system(s) affected.
Reference
Brunello F, Tirelli F, Pegoraro L, Dell'Apa F, Alfisi A, Calzamatta G, Folisi C, Zulian F. New Insights on Juvenile Psoriatic Arthritis. Front Pediatr. 2022 May 26;10:884727. doi: 10.3389/fped.2022.884727. PMID: 35722498; PMCID: PMC9199423.