Problem Representation

Addresses 3 components 1) Who is the patient (healthy, premature, immunocompromised)? 2) What is the time course (acute, subacute, chronic, intermittent)? 3) What is the syndrome or key features of the case?

HPI 14 yo boy presents with headache, fever and joint pains. Symptoms began 1 week ago and have gradually worsened. He is now seeking care due to pain while walking severe enough that he was sent home from school yesterday. Also complains of neck stiffness and burning eyes. He denies sick contacts or recent travel. He denies cough, congestion or rhinorrhea. Symptoms initially better with ibuprofen but now largely unresponsive. ROS: 2-3 abdominal pain, diarrhea 2wk ago PMH: Cystic acne, on doxycycline and topical retinoid SH: Never sexually active FH: No history of autoimmune disease

Problem Representation #1 #2 Previously healthy Acute onset Headache, fever, eye and neck pain with diffuse arthralgias Previously healthy Acute onset Non-traumatic joint pain resulting in inability to bear weight with constitutional symptoms

Dual Process Theory System 1 = Fast / Heuristic System 2 = Slow / Deliberate Improves with practice Library of illness scripts for comparison Allows you to move quickly Workup = the usual Easily biased Availability bias (just saw 3 things that looked like this) Helps identify/reconcile biases Reject any Dx given to you Must consider multiple systems Logic doesn’t make up for lack of knowledge Time consuming and requires a framework for decision making Isolated symptoms can be red herings

System 1: Not unlikely + Could kill you #1 #2 Bacterial Meningitis Septic Arthritis

System 2: My illness scripts don’t line up #1 #2 Meningitis Viral Less likely bacterial Viral Syndrome Reactive Arthritis Infectious Arthritis Autoimmune Arthritis Less likely: Endocarditis with septic arthritis

EXAM VS: 100.2F, HR 88, RR14, BP 104/68, Wt. 138lbs, Ht 5’11’’ Gen: uncomfortable but non-toxic, well nourished Skin: no rashes or bruising HEENT: Bilateral non-exudative conjunctivitis, PERRL and EOMI with intact visual acuity CV, PULM, GI: unremarkably normal for age MSK: limited flexion of R knee with associated joint warmth/tenderness, bilateral ankle pain with passive ROM, right 1st and 2nd MCP TTP, uses arms to assist with rising from chair, limping NEU: no nuchal rigidity, CN 2-12 intact, strength 5/5 in all extremities

Key features Polyarthritis, asymmetrical Acute onset Conjunctivitis Constitutional symptoms No nuchal rigidity, no murmur, no skin findings, stable vitals

LABS CBC: 11k WBC (nl. diff), Hb11, Plt 220 CMP: 141/4.2/111/23/14/0.7 22/29/112/0.2/7.4/3.9 ESR: 65 CRP: 4.5 ANA: negative

Dx: Reactive arthritis Presumed secondary to prior diarrheal illness. Instructed to schedule NSAIDs and RTC in 2-3 if not improving.

Dx: Reactive arthritis Presumed secondary to prior diarrheal illness. Instructed to schedule NSAIDs and RTC in 2-3 if not improving. Needless to say (otherwise wouldn’t be MR) he didn’t get better… Now has swelling and warmth of both knees, multiple MCPs, left elbow with ongoing intermittent fevers up to 102.3.

Problem Representation (ongoing) 14yo with acute onset progressive polyarthritis and fever despite scheduled NSAIDs. Back to system 2…

What could we have missed? Systemic symptoms Not contiguous per anatomy What causes systemic symptoms Cytokines due to occult infection Inflammation 2/2 vasculitis Hematogenous infection: rickettsial infection or culture negative endocarditis

Any exposures?? Doxycycline (but not a new Rx) Could this be a drug-induced autoimmune syndrome?

LABS CBC: 18k WBC (nl. diff), Hb10.8, Plt 270 ESR: 105 CRP: 7.2 ANA: positive Anti-histone Ab positive 1:240 titer Anti-ssDNA Ab positive 1:60 titer

Problem representation 14yo with chronic doxycycline use, acute onset polyarthritis with constitutional symptoms and elevated inflammatory markers in the setting of + anti-histone Ab Dx: Drug induced Lupus

How did we screw this up?? 1) Didn’t recognize connection between doxycycline and drug-induced lupus 2) Closed prematurely due to availability bias or other bias 3) Simmons made me do it

Compare and Contrast SLE DILE + ANA + FHx Renal, skin involvement Women >> Men Requires long term immunosuppression + Drug exposure + anti-ssDNA, anti-histone Joint Sx >> Renal or skin Women = Men Improves with removal of offending agent