19.3 Juvenile Idiopathic Arthritis, HSP & Autoimmune Red Flags

Rheumatology is clinical category #21 on the CPNP-PC outline — lower volume than dermatology, still a place where delayed referral costs a joint or an eye. Domain II wants arthritis that has lasted, purpura you can feel, and autoimmune red flags. Domain III wants ophthalmology on the calendar, serial UA after HSP, and no methotrexate from the office sample closet. Kawasaki disease diagnosis and IVIG live in infectious diseases (13.1); here you only own coronary follow-up. You are not a pediatric rheumatologist. You are the person who does not call a swollen knee growing pains.

Quick Answer: JIA: joint findings ≥6 weeks, morning stiffness, limp → refer rheumatology; uveitis screening with ophthalmology, especially oligoarticular ANA+. HSP (IgA vasculitis): palpable purpura, arthritis, abdominal pain, renal involvement → follow UA. Growing pains: bilateral, evening, normal morning exam. Lyme arthritis: endemic swollen knee. SLE clues: refer. Do not start systemic immunosuppression in primary care. After Kawasaki: cardiology/echo follow-up, not office IVIG.

Clinic opening. A 4-year-old girl limps in the morning, loosens up by noon, and has a mildly swollen left knee for two months. Eyes look white. If you diagnose growing pains and skip both rheumatology and a slit-lamp exam, you missed silent uveitis.

JIA is six weeks — and the eye can be quiet

Juvenile idiopathic arthritis (JIA) is arthritis with no other explanation lasting ≥6 weeks with onset before the 16th birthday. One swollen, warm, limited joint counts. Morning stiffness and a limp that improves later in the day are classic. Guarding, leg-length difference from chronic knee synovitis, and a child who “just won’t jump” are musculoskeletal, not behavioral, until you examine the joint.

Categories you must recognize at a CPNP-PC level (you do not need every ILAR subtype footnote):

• Oligoarticular — four or fewer joints in the first 6 months; often a preschool girl with a knee or ankle. Highest risk of chronic anterior uveitis that is asymptomatic until synechiae and vision loss. ANA-positive oligo JIA is the exam’s uveitis poster child.
• Polyarticular — five or more joints; rheumatoid-factor-positive disease behaves more like adult RA and needs prompt specialty DMARDs.
• Systemic — daily quotidian fever, evanescent rash, serositis, adenopathy, organomegaly — overlapping the Kawasaki/oncology/infection differential. These children are ill. They do not get a three-month NSAID trial at home.

Uveitis screening is ophthalmology, not a flashlight. You cannot see chronic anterior uveitis with a red-reflex check. Refer to pediatric ophthalmology for slit-lamp examinations on the rheumatology/ophthalmology schedule — especially oligoarticular ANA-positive children, who may be screened as often as every 3 months early in disease. A white, comfortable eye does not clear the child. Red, photophobic, painful eyes are acute uveitis — same-week specialty care, not “allergy drops.”

Primary-care management while the referral is moving: NSAIDs may comfort a single joint; rest and school notes; do not start systemic immunosuppression (methotrexate, biologics, chronic high-dose steroids) in primary care. Those drugs need rheumatology, labs, infection screening, and vaccine planning. Intra-articular steroids are a rheumatologist’s procedure.

Clinic vignette. ANA-positive 3-year-old with two months of a swollen knee: rheumatology and ophthalmology. Do not wait for the eye to turn red. Do not start methotrexate from the office.

HSP (IgA vasculitis): feel the purpura, follow the urine

Henoch–Schönlein purpura, now IgA vasculitis, is the common small-vessel vasculitis of childhood. Core cluster:

1. Palpable purpura on the buttocks and lower extremities (the child is often well enough to walk in).
2. Arthritis or arthralgia, often ankles and knees, migratory.
3. Abdominal pain, sometimes occult blood; intussusception is the surgical emergency in this disease.
4. Renal involvement — hematuria, proteinuria, occasionally hypertension or evolving nephritis.

Diagnosis is clinical in a typical child. You still obtain UA, blood pressure, and a renal panel as indicated, and you think about thrombocytopenia (this is not ITP — platelets are usually normal and the purpura is palpable). Steroids for severe abdominal pain are a specialty/hospital decision, not an automatic primary-care taper. Most kids are supportive care: hydration, pain control (avoid NSAIDs if renal involvement is significant), activity as tolerated.

Nephritis can lag. Hematuria or proteinuria may appear days to weeks after the rash fades. Serial urinalysis follow-up (and BP) for months is part of the diagnosis, not optional. Persistent heavy proteinuria, hypertension, rising creatinine, or nephritic/nephrotic features go to nephrology. Recurrence of rash can happen; each flare still gets a urine check.

Growing pains are not inflammatory arthritis

Families will offer “growing pains” for every limp. The label is allowed only when the pattern is classic and the exam is normal.

Unilateral night pain, a swollen joint, fever, refusal to bear weight, back pain in a young child, and systemic features are not growing pains. Recheck. The musculoskeletal chapter owns septic hip and SCFE; this chapter owns the inflammatory morning.

Lyme arthritis, SLE red flags, Kawasaki follow-up only

Lyme arthritis (late disseminated Borrelia burgdorferi in an endemic area) is typically a swollen large joint, especially the knee, with stiffness that is often out of proportion to pain — the child may still walk. There may be no recalled tick or erythema migrans. Diagnosis is serology (two-tier testing) when the joint looks like this, not a PCR of everything. Treatment is antibiotic (doxycycline is acceptable in this indication even in younger children per current AAP/Red Book teaching) for a defined course; rheumatology or infectious disease when the joint is chronic, confusing, or not responding. Do not start a JIA biologic for an untreated endemic swollen knee you never tested. Early erythema migrans treatment without serology delay remains an infectious-disease skill (chapter 13).

SLE red flags in a school-age child or adolescent (more often girls): malar or discoid rash, photosensitivity, oral or nasal ulcers, inflammatory arthritis, unexplained cytopenias, proteinuria or casts, serositis, seizures or psychosis, Raynaud, alopecia. ANA is a screen with false positives — a positive ANA in an otherwise well child with nonspecific aches is not lupus. A compatible multi-system picture plus ANA is same-specialty rheumatology, plus urinalysis and CBC today. Do not start systemic immunosuppression in primary care. Do not start high-dose steroids for “possible SLE” before infection and malignancy are considered with the receiving team.

Kawasaki disease acute diagnosis, incomplete criteria, IVIG, and aspirin are hospital treatments — already taught in 13.1. This section’s only job: after discharge, primary care coordinates coronary follow-up. Cardiology sets the echocardiogram schedule, activity limits, and duration of antiplatelet therapy. Live vaccines are delayed after IVIG per Red Book intervals. You do not repeat IVIG in clinic at the 6-week visit. You do not stop aspirin on a hunch. You do not skip the cardiology appointment because the child “looks fine.”

Refer rheumatology — do not immunosuppress in PC

Refer when arthritis lasts toward or beyond 6 weeks, when uveitis is possible, when HSP urine is not trivial and not resolving, when Lyme arthritis is chronic or unclear, when SLE features cluster, when systemic JIA fever is in the room, and when you cannot distinguish leukemia from rheumatic disease (bone pain, cytopenias — oncology first if that race is on).

Do not start methotrexate, TNF inhibitors, chronic systemic corticosteroids, cyclophosphamide, or “a little prednisone to see” as a primary-care experiment. NSAIDs and referral letters are your lane. Infection, live-vaccine status, TB screening, and pregnancy counseling belong with the prescriber of the immunosuppressant.

Exam traps.

1. Growing pains labeled on a swollen morning joint.
2. Skipping ophthalmology in oligo ANA+ JIA because the eyes are white.
3. Starting methotrexate or steroids in primary care.
4. Treating HSP as ITP (palpable purpura, normal platelets).
5. Discharging HSP without UA follow-up.
6. Calling an endemic swollen knee JIA without Lyme serology.
7. Calling a lone positive ANA lupus.
8. Repeating Kawasaki IVIG in the office instead of coronary follow-up.

Clinic close. Six weeks of joint swelling: JIA language, rheumatology, slit-lamp uveitis screening. Palpable purpura on the legs: HSP, watch the gut, follow the urine. Nighttime bilateral aches, normal exam: growing pains. Endemic puffy knee: think Lyme. Malar rash plus cytopenias plus protein: SLE, refer, no homemade immunosuppression. Former Kawasaki patient: echo and cardiology, not another dose of IVIG from clinic.