Papineau v Romero-Sierra: When a Lyme Disease Claim Fails at the Diagnosis

A missed-diagnosis malpractice claim has three substantive elements at the causation stage: the plaintiff must prove they had the alleged condition; the plaintiff must prove that the clinical picture permitted earlier diagnosis; and the plaintiff must prove that earlier diagnosis would have produced a better outcome. Failure at any of the three defeats causation. The most fundamental failure is at the threshold — where the plaintiff cannot establish, on a balance of probabilities, that they ever had the condition the defendant is alleged to have missed.

Papineau v Romero-Sierra et al, 2024 ONSC 1659, illustrates this threshold failure. An Ontario man brought claims against two eastern Ontario physicians — an emergency department physician at Kemptville District Hospital who first saw him after a possible bite, and his long-time family physician — alleging negligent failure to diagnose Lyme disease over a two-year period. The trial judge dismissed the action. The decision turned on multiple findings: that neither physician breached the standard of care, and that the plaintiff failed to prove he had Lyme disease at all. The hypothetical damages calibration ($100,000 in general damages against the ER physician if both SOC breach and Lyme disease had been established) was academic.

The case is doctrinally significant because it engages several distinct frameworks together: the standard-of-care analysis applied to ER and family practice in the context of suspected Lyme disease; the credibility framework that prefers contemporaneous documentation over patient recollection; the Wilson v Swanson error-of-judgment doctrine in its successful defendant deployment; the multi-component causation framework for missed diagnosis; and the litigation ethics doctrine on aggressive accusations against professional defendants. The case is also the second Lyme disease case in the rewritten cluster on this site, joining Beazley v Johnston (summary judgment for expert qualification failure) to provide comprehensive coverage of Lyme disease malpractice litigation patterns.

The clinical context: Lyme disease in Ontario

Lyme disease is caused by the bacterium Borrelia burgdorferi. The pathogen is transmitted by blacklegged ticks (Ixodes scapularis in Ontario; I. pacificus in western North America). For transmission to occur, the tick must typically remain attached to the host for 24 to 36 hours or more — enough time for the bacterium to migrate from the tick’s midgut to its salivary glands and into the host.

Ontario has growing endemic areas for blacklegged ticks, particularly in eastern Ontario (the Kingston region, the lower Ottawa Valley, and parts further east), southern Ontario along Lake Erie, and increasingly in other parts of the province as climate change extends the tick’s range. The seasonality is broadly late spring through early fall, when nymphal and adult ticks are most active.

Early Lyme disease (3 to 30 days after a tick bite) is characterized by:

• Erythema migrans (EM): a circular or oval rash, typically painless, that expands centrifugally from the bite site
• Sometimes accompanied by fever, fatigue, headache, and arthralgia
• The rash typically appears 3 days to 30 days post-bite (the medical literature cites a median onset of approximately 7 days)

The EM rash is the hallmark physical finding. Its clinical characteristics matter:

• Typically painless or only mildly pruritic
• Expands over days
• Often has a characteristic “bullseye” appearance (central clearing) but not always
• Not warm or particularly tender on palpation in most cases

By contrast, cellulitis — a bacterial skin and soft tissue infection — typically presents as:

• A red, warm, tender, sometimes painful area of skin
• More rapid onset than EM
• Often associated with a clear entry point or trauma
• Responds to antibiotics like amoxicillin or cephalexin

The two conditions can look similar at first glance, but the timing, the pain profile, and the temperature of the lesion are clinical distinguishing features. The treatment differs: cellulitis requires standard antibacterial treatment for skin and soft tissue infection; Lyme disease (where established or strongly suspected) requires Lyme-specific antibiotic therapy (typically doxycycline for adults; amoxicillin in certain populations).

Untreated Lyme disease can progress over weeks to months to disseminated infection with cardiac (carditis, AV block), neurologic (meningitis, cranial neuropathy, radiculopathy), or articular (oligoarticular arthritis, particularly knee) manifestations. Treatment remains effective at this stage but becomes more complex.

“Chronic Lyme disease” is a contested diagnostic category. Some practitioners, particularly in parts of the United States, diagnose patients with chronic Lyme disease based on symptom complexes that do not meet mainstream Canadian or American diagnostic criteria. Mainstream medical consensus distinguishes this contested category from “post-treatment Lyme disease syndrome” (PTLDS), which is recognized but distinct: PTLDS describes residual symptoms after appropriate treatment of confirmed Lyme disease and is approached cautiously by Canadian clinicians.

This clinical landscape matters for the analysis in Papineau. The plaintiff’s claim depended on his having had Lyme disease. The defence position was that he never had Lyme disease at all — that his initial rash was cellulitis, that his subsequent symptoms were not Lyme-related, and that the US diagnosis he received was unreliable. The trial judge’s analysis worked through these clinical questions carefully.

The substantive facts

April 14, 2010 — the KDH emergency department visit. Around 11 p.m., the plaintiff presented to Kemptville District Hospital’s emergency department concerned about a possible bite and a rash. The triage nurse documented that the plaintiff had been “out cutting wood yesterday a.m.” and had “got bit by an insect.” Dr. Brisebois, the family physician working in the ED, documented that the bite had occurred about 36 hours earlier and that the plaintiff thought he had been bitten by an insect and not a tick. Dr. Brisebois examined the rash, diagnosed cellulitis and sinusitis, prescribed amoxicillin for 10 days, and discharged the plaintiff with instructions to return if the rash developed into EM. The reference to EM in the discharge instructions confirmed that Dr. Brisebois had considered Lyme disease in the differential.

2010 to 2012 — the family practice period. The plaintiff was the long-standing patient of Dr. Romero-Sierra, a family physician. The plaintiff later alleged that he had repeatedly raised Lyme disease concerns with Dr. Romero-Sierra over the following two years, and that Dr. Romero-Sierra had repeatedly dismissed those concerns. The contemporaneous clinical record did not clearly support this allegation.

November 29, 2011 — the Lyme screening test. At the end of a 40-minute double counselling session focused on the plaintiff’s depression and anxiety, Dr. Romero-Sierra issued a requisition for a Lyme disease screening test without first asking the plaintiff why he wanted the test. The test result is not specifically reported in the decision but the issuance of the requisition and the subsequent diagnostic trajectory imply a negative result.

September 2012 — the US diagnosis. The plaintiff was diagnosed with Lyme disease in the United States by Dr. McShane. The Canadian medical record contained no parallel diagnosis. Dr. McShane subsequently prescribed treatment that Dr. Romero-Sierra agreed to rewrite under Canadian prescription rules — despite Dr. Romero-Sierra not believing the plaintiff had Lyme disease.

The standard-of-care analysis: Dr. Brisebois

The plaintiff’s theory against Dr. Brisebois was that the ER physician should have:

• Treated the bite as a possible tick bite rather than an insect bite
• Considered Lyme disease prophylaxis (single-dose doxycycline is the standard prophylactic regimen following high-risk tick exposure)
• Prescribed antibiotics that would have prevented Lyme disease from developing

The trial judge found no breach. The key findings:

The bite was reported as an insect bite, not a tick bite. The triage nurse’s notes and Dr. Brisebois’s notes both recorded that the plaintiff said he had been bitten by an insect. The plaintiff at trial disputed this and said he had told Dr. Brisebois he had been bitten by a tick. The trial judge accepted the contemporaneous notes over the trial testimony — for reasons addressed below.

Dr. Brisebois nonetheless considered Lyme disease. The discharge instructions specifically referenced EM. This is documentary evidence that Dr. Brisebois recognized the possibility of Lyme disease even though the patient had described an insect bite. He provided appropriate safety-netting (return if rash develops into EM) consistent with prudent ER practice.

The amoxicillin was for cellulitis and sinusitis. The plaintiff argued that the amoxicillin should have been understood to have an incidental anti-Lyme effect. The trial judge found that the prescription was for the diagnosed conditions and that the dose and duration were appropriate for those conditions, not for Lyme prophylaxis.

The clinical picture did not support Lyme disease. The rash characteristics (painful, swollen, warm — consistent with cellulitis) and the timing (within 36 hours of the bite — too early for EM) did not support a Lyme diagnosis on the clinical picture available to Dr. Brisebois.

No breach of the standard of care.

The standard-of-care analysis: Dr. Romero-Sierra

The plaintiff’s theory against Dr. Romero-Sierra was that the family physician had repeatedly dismissed Lyme disease concerns over a two-year period and had thereby delayed diagnosis. The plaintiff also pointed to specific aspects of the practice, particularly the November 2011 test requisition issued without inquiry into why.

The trial judge found no actionable breach of the standard of care. The key findings:

The November 2011 requisition was within the standard. The trial judge agreed in principle that a physician should generally not order a diagnostic test without first determining why the patient is requesting it. But this was a judgment call within the Wilson v Swanson framework — particularly given the context: the request came at the end of a 40-minute double counselling session about depression and anxiety. Dr. Romero-Sierra’s reasoning, accepted at trial, was that anxious patients requesting Lyme testing often find negative results reassuring. The decision to issue the requisition in the expectation of a negative result that would relieve the patient’s anxiety was a clinical judgment within the range of reasonable practice.

A non-pleaded breach. The trial judge did find that Dr. Romero-Sierra fell below the standard by agreeing to rewrite Dr. McShane’s prescriptions when he did not believe the plaintiff had Lyme disease. But this conduct was not pleaded in the statement of claim. The plaintiff’s pleaded allegations were limited to failure to diagnose and failure to prescribe proper medication. The court cannot find liability for unpleaded misconduct.

The remaining allegations were unsupported. The plaintiff’s broader allegations of dismissive treatment over the two-year period did not have clear contemporaneous support in the clinical record. The trial judge did not find a pattern of breach beyond what was directly engaged at trial.

The contemporaneous notes doctrine

A doctrinally important feature of Papineau is the trial judge’s analysis of why the triage nurse’s notes and Dr. Brisebois’s notes were accepted over the plaintiff’s later recollection. The reasoning, distilled, was:

• The notes were consistent with each other (independent sources converging on the same account)
• They were made by two different people who had spoken to the plaintiff separately
• They were made while or shortly after the interactions occurred (contemporaneous documentation)
• The note-makers had professional credibility and no apparent reason to misstate the patient’s account
• The plaintiff could not provide a satisfactory explanation for why the notes differed from his recollection

This is a clean articulation of when contemporaneous documentation should prevail over later testimony. The framework is doctrinally important well beyond malpractice — it operates in any case where the trier of fact must choose between contemporaneous documentation and witness recollection at trial. The key factors are the independence of the documentary sources, the timing of the documentation, the credibility of the document-makers, and the absence of any plausible explanation for the discrepancy.

For plaintiff counsel, the framework is a reminder that the medical record is a powerful evidentiary instrument. Plaintiffs whose accounts contradict the contemporaneous record face a substantial uphill battle at trial. The accounts must either be supported by other documentary evidence or must be accompanied by a credible explanation for the discrepancy.

For defence counsel, the framework underscores the importance of accurate, contemporaneous note-taking by ER staff and family physicians. Where the notes are clean, consistent, and made by reliable sources at the time of the events, they will typically prevail over later patient testimony.

The “judgment call” doctrine in successful defendant application

The trial judge’s analysis of Dr. Romero-Sierra’s November 2011 test requisition is a clean illustration of the Wilson v Swanson, [1956] SCR 804, error-of-judgment doctrine successfully deployed by a defendant.

The doctrine holds that a physician who exercises reasonable clinical judgment does not breach the standard of care merely because the judgment was suboptimal or because other physicians might have done differently. The standard requires reasonable practice within a range, not perfect practice or unanimity.

In Papineau, the trial judge found that Dr. Romero-Sierra’s decision was suboptimal in one respect (he should generally have asked the patient why before ordering the test) but reasonable in the broader context (the test was non-invasive, the patient was anxious, the likely negative result would relieve anxiety, and the session had already run 40 minutes). The judgment fell within the range of reasonable practice even if it was not the textbook approach.

This is the standard application of Wilson v Swanson. Where the physician has actually exercised clinical judgment (not simply allowed time to pass), and where the judgment falls within a range of reasonable practice, the doctrine protects the choice. This is the framework recently engaged in Henry v Zaitlen where the doctrine failed (because there was no judgment, only inaction). In Papineau it succeeded (because the judgment was actually exercised within a defensible range).

The causation analysis: the “no Lyme disease” defeat

The trial judge’s causation analysis is doctrinally distinctive because it identifies a complete causation defeat at the most fundamental level: the plaintiff did not prove he had Lyme disease at all. Without proof of the underlying condition, the entire missed-diagnosis framework collapses.

The reasoning components:

The bite was reported as an insect bite. The plaintiff was an experienced outdoorsman who had encountered ticks before. He told both the triage nurse and Dr. Brisebois that he had been bitten by an insect, not a tick. While he could have been mistaken, he was in the best position to observe what had bitten him. The trial judge accepted the contemporaneous account.

The timing was inconsistent with EM. The trial judge found that the bite occurred on April 13 (the day before the ER visit), based on the triage note (“yesterday”) and Dr. Brisebois’s note (“36 hours earlier”). The rash was present at the time of the ER visit, which means it appeared within 24 to 36 hours of the bite. EM typically does not appear until at least 3 days after a tick bite, and more commonly 7 to 14 days. A rash that appears within 36 hours is not EM.

The rash characteristics were inconsistent with EM. The rash was painful, swollen, and warm — characteristic of cellulitis. EM is typically painless and not warm. The clinical picture supported cellulitis, not Lyme disease.

The Canadian ER assessment was contemporaneous. Dr. Brisebois saw the rash at the time, spoke with the patient, and diagnosed cellulitis. This is the contemporaneous clinical assessment by a treating physician seeing the patient in real time.

The US diagnosis was unreliable. Dr. McShane, the US physician who diagnosed Lyme disease, did not have the relevant Canadian clinical information when she made the diagnosis. She did not know that the patient had described the bite as an insect bite, that the rash had appeared within 36 hours, that the rash was painful and warm, or that the Canadian ER physician had diagnosed cellulitis. Without this information, her diagnosis could not displace the contemporaneous Canadian clinical assessment.

The result: the plaintiff failed to prove he had Lyme disease. The causation framework collapsed at the threshold.

The chronic Lyme disease controversy

The trial judge’s analysis carefully rejected Dr. McShane’s diagnosis on fact-specific grounds (incomplete clinical information) rather than on a wholesale rejection of “chronic Lyme disease” as a diagnostic category. This is a measured judicial posture.

The broader doctrinal posture nonetheless matters. Where a Canadian patient receives a US chronic Lyme disease diagnosis based on incomplete clinical information, and where the contemporaneous Canadian clinical record contradicts the US diagnosis, the Canadian record will typically prevail for malpractice litigation purposes. This is not a rule against US diagnoses generally; it is an evidentiary preference for contemporaneous, complete, clinically grounded assessments over remote, retrospective, partial-information assessments.

For Ontario plaintiffs considering Lyme disease malpractice claims based on US diagnoses, the implications are significant:

• The US diagnosis alone will rarely be sufficient
• The Canadian clinical record will be the principal evidence
• Reconciling the two — with credible expert testimony from a properly qualified Canadian Lyme specialist — is the analytical work the plaintiff must do
• Reliance on contested chronic Lyme disease theories is unlikely to succeed in Ontario courts

The litigation ethics doctrine

A doctrinally distinctive feature of Papineau is the trial judge’s express commentary on the plaintiff’s counsel’s tactics at trial. The plaintiff’s counsel had accused Dr. Romero-Sierra of:

• Lying about multiple matters
• Destroying hospital records
• Fabricating notes
• Over-billing OHIP

The trial judge found no evidence of dishonesty despite some contradictions in Dr. Romero-Sierra’s testimony. More importantly, the trial judge expressly criticized the tactical choice to make these accusations. The reasoning, paraphrased: litigants should be hesitant to accuse other litigants of dishonesty, particularly where the litigant on the receiving end is a professional whose reputation is essential to their livelihood. Dr. Romero-Sierra did not deserve the treatment he received from the plaintiff and his counsel at trial.

This is a meaningful precedent on the limits of accusation-based litigation strategy against medical professional defendants. The implicit framework:

• Accusations of professional dishonesty are not routine pleading material
• They require evidentiary foundation, not strategic deployment
• They cause real reputational harm to the defendant regardless of trial outcome
• Counsel making the accusations bear a heightened obligation to ensure the accusations are supported
• Where the trial judge finds the accusations unsupported, judicial commentary can attach to the tactic

For plaintiff counsel evaluating accusations of professional dishonesty in malpractice cases, the lesson is one of restraint. Accusations of fabrication, document destruction, or fraud should be reserved for cases where the documentary evidence supports them. Casual deployment of these accusations as a tactical pressure mechanism is unlikely to succeed and may attract judicial criticism.

The hypothetical damages calibration

The trial judge addressed damages hypothetically: if Dr. Brisebois had breached the standard of care and the plaintiff had Lyme disease, general damages would have been $100,000 against Dr. Brisebois only. No damages would have been assessed against Dr. Romero-Sierra because the plaintiff did not raise Lyme disease with Dr. Romero-Sierra until November 2011 — by which time the window for preventing the development of Lyme disease (if the plaintiff had been infected in April 2010) would have closed.

The $100,000 hypothetical quantum is a useful reference for early-stage Lyme disease general damages where the SOC breach and causation framework would otherwise support liability. The breakdown of the broader damages framework (loss of earnings, future care costs) was not addressed because the hypothetical did not engage them in detail.

Comparison: Papineau and Beazley

The two Lyme disease cases in the rewritten cluster produce defendant-favourable outcomes for distinct reasons:

• Beazley v Johnston: Ontario summary judgment. The plaintiff tendered expert evidence, but the expert was disqualified at the White Burgess Langille Inman v Abbott and Haliburton Co, 2015 SCC 23, qualification stage. Without a qualified expert, no genuine issue for trial; summary judgment for the defendant.
• Papineau v Romero-Sierra (this case): Ontario trial dismissal. The trial proceeded with expert evidence. The court found no SOC breach by either physician and, separately, found that the plaintiff failed to prove he had Lyme disease at all. Multiple grounds of dismissal.

Together the two cases illustrate the structural challenges in Ontario Lyme disease malpractice litigation:

• Qualified Canadian Lyme disease experts willing to testify for plaintiffs are not plentiful
• The contemporaneous clinical record will typically prevail over patient recollection
• US diagnoses, particularly those reflecting chronic Lyme disease theories, do not displace the Canadian record
• The clinical features of EM and Lyme disease are clinically specific and require careful evidentiary grounding
• The causation framework operates at multiple levels — failure at the threshold (no underlying condition) is the most fundamental

The doctrinal lessons

The case stands for several propositions.

Causation can fail at the threshold. In missed-diagnosis cases, the plaintiff must prove they had the alleged condition. Failure to prove the underlying condition defeats causation regardless of any standard-of-care analysis. This is a more fundamental defeat than the typical “earlier diagnosis would not have changed the outcome” causation defeat.

Contemporaneous notes typically prevail over patient recollection. Where multiple independent contemporaneous notes converge on an account, and the patient’s later testimony differs without persuasive explanation, the notes will typically prevail. The principle applies to triage notes, ER notes, family physician notes, and other clinical documentation.

The “judgment call” defence requires actual judgment. Wilson v Swanson protects clinical decisions made within a range of reasonable practice. Where the physician has actually exercised judgment (here, balancing the patient’s anxiety, the non-invasive nature of the test, and the expected reassurance of a negative result), the doctrine applies. Where there is no judgment, only inaction (as in Henry v Zaitlen), the doctrine does not protect.

The clinical picture matters more than retrospective characterization. Where the rash characteristics (timing, pain, warmth) do not match EM and do match cellulitis, the diagnosis at the time was correct. Subsequent retrospective characterization by other clinicians (here, a US physician without complete information) does not change the clinical picture that the treating physician faced.

US diagnoses do not automatically establish Ontario clinical reality. Where a US clinician diagnoses Lyme disease based on incomplete information about the Ontario clinical presentation, the diagnosis is not determinative for Ontario malpractice litigation. The Canadian clinical record will typically prevail.

Accusations of professional dishonesty require evidentiary foundation. Trial counsel should not deploy accusations of fabrication, document destruction, or fraud against professional defendants without supporting evidence. Casual or tactical deployment can attract judicial criticism and damage the professional defendant’s reputation regardless of trial outcome.

Unpleaded breaches cannot support liability. A trial judge may identify conduct that fell below the standard during the evidence, but if that conduct was not pleaded, it cannot support liability. The pleading defines the scope of the case.

Why this case matters

For prospective clients considering Lyme disease malpractice claims. The case illustrates how challenging these claims can be when the contemporaneous Canadian clinical record does not support the underlying diagnosis. Where the original Canadian ER assessment identified cellulitis, the timing did not match EM, and the rash characteristics did not match EM, a subsequent US Lyme disease diagnosis based on incomplete information is unlikely to support a successful malpractice claim. For prospective clients, the realistic assessment matters at the outset. For more on this, see Suing for Medical Malpractice in Ontario: What You Need to Know and Six Common Misunderstandings About Medical Malpractice.

For plaintiff counsel. The case is a reminder of the structural importance of the contemporaneous clinical record and the limits of accusation-based litigation strategy. Where the contemporaneous record contradicts the plaintiff’s account, that record will typically prevail. Where the proposed expert testimony comes from a US clinician working with incomplete information, the diagnosis will face substantial evidentiary challenges. Where the plaintiff’s case requires aggressive accusations of professional dishonesty against the defendant physicians, those accusations must be supported by evidence or they will attract judicial criticism.

For defence counsel. The case is useful precedent on multiple fronts: the contemporaneous notes framework; the Wilson v Swanson judgment-call defence; the “no underlying condition” causation defeat; and the litigation ethics commentary on aggressive accusations. The trial judge’s express statements protecting the professional defendant’s reputation from unsupported accusations are particularly noteworthy.

For ER physicians and family physicians managing possible Lyme disease presentations. The case is a reminder that:

• Careful documentation of the patient’s account is the foundation of the clinical record
• Differential diagnosis should include Lyme disease where the clinical context warrants
• Discharge instructions referencing EM and clear return-to-care advice operate as both clinical safety-netting and documentary protection
• The clinical features of EM (timing, painless presentation, expansion pattern) should be assessed carefully when ruling out Lyme disease
• The “judgment call” defence will protect reasonable clinical decisions within a range of acceptable practice

For more on Ontario missed-diagnosis malpractice generally, see Misdiagnosis Lawyer in Toronto and Five Dangerous ER Misdiagnoses. For more on the contrast between this case and the Henry v Zaitlen successful failure-to-investigate case, see Henry v Zaitlen: A Jury Verdict for Delayed Diagnosis of a Spinal Cord Fistula.

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Decision Date: April 8, 2024

Jurisdiction: Ontario Superior Court of Justice

Citation: Papineau v Romero-Sierra et al, 2024 ONSC 1659 (CanLII)

Key authorities: Wilson v Swanson, [1956] SCR 804 (error of judgment doctrine); Crits v Sylvester, [1956] OR 132 (CA), aff’d [1956] SCR 991 (standard of care framework); ter Neuzen v Korn, [1995] 3 SCR 674 (expert evidence requirement); Clements v Clements, 2012 SCC 32 (but-for causation); Henry v Boivin, 2023 ONSC 6632 (cited at trial for standard of care formulation)