Most commonly misdiagnosed medical conditions

By Naveed Saleh, MD, MS, for MDLinx
Published January 19, 2024

Key Takeaways

The prospect of misdiagnosing a patient’s medical condition will put a lump in any doctor’s throat. However, the error seems remarkably common, with some estimates pegging misdiagnoses among 12 million Americans, or 1 in every 20 patients, each year. Let’s take a look at some commonly misdiagnosed conditions.


Failure to diagnose stroke quickly can lead to lost opportunity to initiate time-sensitive treatments.

In 2% to 26% of patients, stroke is underdiagnosed (ie, false-negative cases or “stroke chameleons”), and in 30% to 43% of patients, stroke is overdiagnosed (ie, false-positive cases or “stroke mimics”).

Common stroke mimics include:

  • Migraine

  • Epileptic seizures or postictal states

  • Psychogenic disease or conversion disorder

  • Toxic-metabolic abnormalities (eg, hyperglycemia and systemic infection)

  • Demyelinating disease

Because atypical stroke presentations, including posterior circulation stroke syndromes, are often misdiagnosed, additional efforts are needed to improve diagnoses in these cases. According to the authors of one review article: “Additional strategies to improve the accuracy of stroke diagnosis should focus on rapid clinical reasoning in the time-sensitive setting of acute ischemic stroke and identifying imperfections in the healthcare system, which may contribute to diagnostic error.”[]

In other words, physicians should be on the lookout for stroke, because time is of the essence.

Irritable bowel syndrome

Irritable bowel syndrome (IBS) is marked by altered bowel habits with abdominal pain devoid of an organic pathological process or specific motility/structural abnormalities. Change in bowel habits, with diarrhea, constipation, or both, is the main symptom in IBS. This condition is the most common reason for referral to a gastroenterologist.

Symptoms of IBS with diarrhea can be mistaken for:

  • Dietary causes (eg, alcohol, lactose, sorbitol, fructose, caffeine, fatty foods, fat substitutes, and gas-producing foods)

  • Inflammatory bowel disease (eg, Crohn’s disease or ulcerative colitis)

  • Malabsorption (eg, celiac disease)

  • Drug toxicity (eg, antibiotics, NSAIDs, and ACE inhibitors)

  • Infections

  • Ovarian cancer

  • Endometriosis

  • Colorectal cancer

  • Carcinoid

The differential diagnosis for IBS with constipation includes:

  • Dietary causes (eg, lack of fiber)

  • Immobility

  • Drug toxicity (eg, opiates, antidepressants, and calcium-channel blockers)

  • Neurological (Parkinson’s disease, multiple sclerosis, and spinal cord injuries)

  • Endocrine disease (eg, diabetes, hypothyroidism, and hypercalcemia)

  • Colorectal cancer

  • Ovarian cancer

  • Bowel obstruction

  • Diverticular disease

Carpal tunnel syndrome vs thoracic outlet syndrome

When presenting with shoulder pain, carpal tunnel syndrome (which involves impingement of the median nerve at the wrist) can easily be confused with thoracic outlet syndrome. However, the co-occurrence of these two syndromes in a single patient is extremely rare.

Thoracic outlet syndrome is a constellation of disorders marked by abnormal compression of arterial, venous, or neural structures in the base of the neck. Symptoms rarely develop until adulthood, and typically result from impingement of the brachial plexus. They include pain, paresthesia, and numbness. Symptoms of ischemia and venous compression secondary to compression of the subclavian artery are uncommon and may predict emboli.

Systemic lupus erythematosus vs rheumatoid arthritis

Systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) are both systemic autoimmune diseases that attack the body, leading to inflammation and tissue damage. The pathogenesis and mechanisms of SLE and RA, however, are not fully known.

Due to the similarity of symptoms, differentiating and treating these diseases is challenging. In the early stages of disease, 80% of patients with SLE or RA have fever and fatigue, making it difficult to distinguish these diseases at this point. However, researchers of one study showed that in the middle to late stages of these conditions, complement C3 and C4 levels were significantly decreased in patients with SLE, while patients with RA had heightened CRP levels.[]

Lyme disease

Lyme disease, which is caused by the spirochete Borrelia burgdorferi, is the most common vector-borne illness in the United States. It is also difficult to diagnose because symptoms are often nonspecific, and clinical presentation varies based on the stage of the illness.

Presentation can include erythema migrans, carditis, central nervous system disease, and arthritis. Despite clinical presentation, most patients with Lyme disease are cured of clinical symptoms following 2 to 4 weeks of treatment with antimicrobials.

Even the diagnosis of erythema migrans, which is pathognomonic for Lyme disease, can sometimes be challenging because the rash doesn’t always appear, or it may be confused with an insect bite, ringworm, cellulitis, nummular eczema, or granuloma annulare.

However, rapid and prolonged extension of erythema migrans when left untreated helps to separate this characteristic rash from differential causes of rash.

On a related note, other causes of carditis include viral agents, specifically Coxsackie enteroviruses. The differential diagnosis for arthritis is long and includes bacterial septic arthritis, and rheumatologic and oncologic processes. Many physicians erroneously believe that nonspecific symptoms in patients, such as arthralgias and fatigue, call for antibody testing for Lyme disease. Indeed, most patients who receive the test do so under these circumstances. Antibody tests for Lyme disease, however, can be highly nonspecific and yield many false positives, thus resulting in unnecessary treatment.

Multiple sclerosis

The misdiagnosis of multiple sclerosis (MS) is an important issue among neurologists, with MS specialist neurologists frequently encountering patients who have received misdiagnoses of MS—sometimes for 10 or more years.

Although a large number of rare genetic, metabolic, vascular, and inflammatory disorders are often posited as part of the differential diagnosis for MS, the conditions most often mistaken for it are common: migraine, fibromyalgia, and functional neurologic disorders. These alternative diagnoses are based on MRI scans done to investigate white matter lesions.

The misdiagnosis of MS can have serious repercussions, including exposure to MS disease-modifying agents, which can result in patient harm, as well as litigation.

On a final note, with a diagnosis of exclusion, misdiagnosis is a common pitfall. For example, IBS is a diagnosis of exclusion, which means that it can only be diagnosed when everything else on the list of differential diagnoses is ruled out. Other examples of diagnoses of exclusion include panic attack, diastolic heart failure, Bell’s palsy, anorexia tardive (ie, later-life anorexia), phantom tooth pain, Alzheimer’s disease, functional vision loss, psychogenic cough, hypertensive encephalopathy, chronic bronchitis, and pyoderma gangrenosum.

Share with emailShare to FacebookShare to LinkedInShare to Twitter