Connective Tissue Diseases
Systemic lupus erythematosus
Childhood SLE is more severe than adult-onset, with higher rates of nephritis and neuropsychiatric disease. The 2019 EULAR/ACR classification requires ANA ≥1:80 as an entry criterion followed by weighted clinical and immunologic criteria. Low complement with rising anti-dsDNA suggests active disease and nephritis. Hydroxychloroquine is baseline therapy for nearly all patients; mycophenolate or cyclophosphamide treats major organ involvement; belimumab and rituximab are options in refractory disease. Neonatal lupus follows maternal anti-Ro/SSA and anti-La/SSB and may cause congenital heart block.
Juvenile dermatomyositis
Proximal weakness, heliotrope rash, Gottron papules, elevated CK and aldolase, and nailfold capillary changes. Calcinosis, lipodystrophy, ulceration, and interstitial lung disease are complications. Corticosteroids plus methotrexate are first line; IVIG and biologics for refractory disease.
Scleroderma, Sjögren, MCTD
Juvenile localized scleroderma (morphea, linear, en coup de sabre) is far more common than juvenile systemic sclerosis, which requires Raynaud phenomenon plus skin induration and warrants pulmonary and cardiac screening. Childhood Sjögren presents with parotid swelling and anti-Ro. MCTD is defined by anti-U1RNP with overlapping features and risk of pulmonary hypertension.
Traps
Do not diagnose SLE from ANA alone. Drug-induced lupus (minocycline, TNF inhibitors) usually spares kidneys and CNS and improves after withdrawal. Malar rash spares the nasolabial folds; seborrheic dermatitis does not.
Rule of thumb
Low complement plus rising anti-dsDNA signals an impending lupus flare, particularly nephritis.