Herpes simplex virus;

My patient with erythema multiforme has tested positive for Mycoplasma pneumoniae IgM antibody. Does this mean she has an acute M. pneumonia infection as the cause of her acute illness?

FA Manian MD, MPH, , , , , , , , , , , , , , , , , , Leave a comment

Not necessarily! Although detection of IgM in the serum of patients has proven valuable in diagnosing many infections during their early phase, particularly before IgG is detected, less well known is that false-positive IgM results are not uncommon. 1

More specific to M. pneumoniae IgM, false-positive results have been reported in 10-80% of patients without a clinical diagnosis of acute M. pneumoniae infection 2-4 and 3-15% of blood donors. 4

False-positive IgM results may also occur when testing for other infectious agents, such as the agent of Lyme disease (Borrelia burgdorferi), arboviruses (eg, Zika virus), and herpes simplex, Epstein-Barr, cytomegalovirus, hepatitis A and measles viruses. 1,5  

Reports of false positive IgM results include a patient with congestive heart failure and mildly elevated liver enzymes who had a false-positive hepatitis IgM which led to unnecessary public health investigation and exclusion from an adult day care center. 1 Another patient with sulfa rash had a false-positive measles IgM antibody resulting in callback of >100 patients and healthcare providers for testing!5

There are many potential mechanisms for false-positive IgM results, including polyclonal B cell activation, “vigorous immune response”, cross-reactive antibodies, autoimmune disease, subclinical reactivation of latent viruses, influenza vaccination, overreading weakly reactive results, and persistence of antibodies long after the resolution of the acute disease. 1,2

In our patient, a significant rise in M. pneumoniae IgG between acute and convalescent samples several weeks apart may be more helpful in diagnosing an acute infection accounting for her erythema multiforme.

 

References

  1. Landry ML. Immunoglobulin M for acute infection: true or false? Clin Vac Immunol 2016;23:540-5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4933779/
  2. Csango PA, Pedersen JE, Hess RD. Comparison of four Mycoplasma pneumoniae IgM-, IgG- and IgA-specific enzyme immunoassays in blood donors and patients. Clin Micro Infect 2004;10:1089-1104. https://www.clinicalmicrobiologyandinfection.com/article/S1198-743X(14)63853-2/pdf
  3. Thacker WL, Talkington DF. Analysis of complement fixation and commercial enzyme immunoassays for detection of antibodies to Mycoplasma pneumoniae in human serum. Clin Diag Lab Immunol 2000;7:778-80. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC95955/
  4. Ryuta U, Juri O, Inoue Y, et al. Rapid detection of Mycoplasma pneumoniae IgM antibodies using immunoCard Mycoplasma kit compared with complement fixation (CF) tests and clinical application. European Respiratory Journal 2012; 40: P 2466 (Abstract). https://erj.ersjournals.com/content/40/Suppl_56/P2466 
  5. Woods CR. False-positive results for immunoglobulin M serologic results: explanations and examples. J Ped Infect Dis Soc 2013;2:87-90. https://www.ncbi.nlm.nih.gov/pubmed/26619450

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My patient with erythema multiforme has tested positive for Mycoplasma pneumoniae IgM antibody. Does this mean she has an acute M. pneumonia infection as the cause of her acute illness?

My patient just developed a fixed drug reaction from ibuprofen. What is the mechanism of this type of skin reaction?

FA Manian MD, MPH, , , , , , , , Leave a comment

Although its mechanism is not full elucidated, fixed drug eruption (FDE) is thought to result from the drug-induced cytotoxic activation of CD8+ memory T cells.1 ,2

In this context, the culprit medication behaves as a hapten that adheres to basal keratinocytes which in turn results in the recruitment of T cells and inflammation.  However, as the inflammation resolves, CD8+  effector-memory T cells remain in the area in question,  setting the stage for more rapid immunologic reaction when the drug is reintroduced.

Why a systemic drug triggers a reaction only at specific sites in the body is a fascinating question. Prior herpes simplex virus (HSV) infection (eg, on the lips or genitalia) may explain some cases.1 Interestingly, despite the absence of prior herpetic lesions, most patients with FDE are seropositive for HSV. Previously traumatized body sites (e.g. from burns or insect bites) may also create an immune microenvironment conducive to FDE.

The classic presentation of FDE is reappearance of a rash in the genitals, perianal areas, hands, and feet within 30 min to 8 hours of taking the culprit medication.3 Look specifically for NSAIDs, tetracyclines, sulfonamides, and aspirin on the patient’s drug list. 4

References

  1. Shiohara, T. Fixed drug eruption: Pathogenesis and diagnostic tests. Curr Opin Allergy Clin Immunol 2009; 9:316-21. https://www.ncbi.nlm.nih.gov/pubmed/19474709
  2. Butler, DF. Fixed Drug Eruptions. Medscape. http://emedicine.medscape.com/article/1336702-overview#a4. Accessed March 26, 2018.
  3. Korkij W, Soltani K. Fixed drug eruptions: A brief review. Arch Dermatol 1984;120:520. https://www.ncbi.nlm.nih.gov/pubmed/6231004
  4. Oakley, A. Fixed Drug Eruption. https://www.dermnetnz.org/topics/fixed-drug-eruption Accessed March 26, 2018.

 

Contributed by Amir Hossein Ameri, Medical Student, Harvard Medical School

My patient just developed a fixed drug reaction from ibuprofen. What is the mechanism of this type of skin reaction?

My patient with acute onset headache, photophobia, and neck stiffness does not have CSF pleocytosis. Could she still have meningitis?

FA Manian MD, MPH, , , , , , , , , , , , , , , , , Leave a comment

Although the clinical diagnosis of meningitis is often supported by the presence of abnormal number of WBCs in the CSF (AKA pleocytosis), meningitis may be present despite its absence.

Among viral causes of meningitis in adults, enteroviruses are associated with lower CSF WBC count compared to herpes simplex and varicella zoster, with some patients (~10%) having 0-2 WBC’s/mm31,2.  Of interest, among children, parechovirus (formerly echovirus 22 and 23) meningitis is characterized by normal CSF findings3.

Though uncommon, bacterial meningitis without CSF pleocytosis has been reported among non-neutropenic adults,  including Neisseria meningitidis, Streptococcus pneumoniae, Hemophilus influenzae, Listeria monocytogenes, E. coli, and Proteus mirabilis4.  A European study also reported normal CSF WBC in nearly 10% of patients with Lyme neuroborreliosis (including meningitis) caused primarily by Borrelia garinii5.

Cryptococcal meninigitis may also be associated with normal CSF profile in 25% of patients with HIV infection6.

 

References

  1. Ihekwaba UK, Kudesia G, McKendrick MW. Clinical features of viral meningitis in adult:significant differences in cerebrospinal fluid findings among herpes simplex virus, varicella zoster virus, and enterovirus infections. Clin Infect Dis 2008;47:783-9. https://www.ncbi.nlm.nih.gov/pubmed/18680414
  2. Dawood N, Desjobert E, Lumley J et al. Confirmed viral meningitis with normal CSF findings. BMJ Case Rep 2014. Doi:10.1136/bcr-2014-203733. http://casereports.bmj.com/content/2014/bcr-2014-203733.abstract
  3. Wolthers KC, Benschop KSM, Schinkel J, et al. Human parechovirus as an important viral cause of sepsis like illness and meningitis in young children. Clin Infect Dis 2008;47:358-63. https://www.ncbi.nlm.nih.gov/pubmed/18558876
  4. Hase R, Hosokawa N, Yaegashi M, et al. Bacterial meningitis in the absence of cerebrospinal fluid pleocytosis: A case report and review of the literature. Can J Infect Dis Med Microbiol 2014;25:249:51. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4211346/pdf/idmm-25-249.pdf
  5. Ogrinc K, Lotric-Furlan S, Maraspin  V, et al. Suspected early Lyme neuroborreliosis in patients with erythema migrans. Clin Infect Dis 2013; 57:501-9. https://www.ncbi.nlm.nih.gov/pubmed?term=23667259
  6. Darras-Joly C, Chevret S, Wolff M, et al. Cryptococcus neoformans infection in France: epidemiologic features of and early prognostic parameters for 76 patients who were infected with human immunodeficiency virus. Clin Infect Dis 1996;23:369-76. https://oup.silverchair-cdn.com/oup/backfile/Content_public/Journal/cid/23/2/10.1093/clinids/23.2.369/2/23-2-369.pdf?Expires=1501035620&Signature=FhHMHUHAMmT3rz4ld8QAMet-weu-BWgm5YR6nA4jjSGVGIeaVlMNPgeOkW2fniiel54HQhIs1Kkp3PpzT1glxhJeZvQiGXQCSOoF-jS1SK7S~kBb-oHs4qsIJzN0OJxNAXfoJi4bl7OeKaLTyIE3P8~slwH0BBi7RncSYVgVR4NkOnFpYgn27~wY7pDSUNWvzGFKoSeYGeM0TsAqna-QmXzodITB5bgr1mO6Q6OGUxCsqRwhr6xNb~4G93oqRcsO19gyUluCE0xYt0KbKWuQxJeh8AbtJkNrS08~XInMR50bQZOUb80j0~dtg9jRTGzXQaDllVByoX2Alr48hlhogw__&Key-Pair-Id=APKAIUCZBIA4LVPAVW3Q
My patient with acute onset headache, photophobia, and neck stiffness does not have CSF pleocytosis. Could she still have meningitis?

Should I consider Powassan virus (POWV) in my patient with acute encephalitis?

FA Manian MD, MPH, , , Leave a comment

POWV is a neuroinvasive arbovirus transmitted by Ixodes ticks (similar to Lyme disease). It has been reported in Canada, Russia and, increasingly, in northeastern states and Great lakes region of United States1. Although many cases occur during warmer months, nearly 30% of cases reported from New York occurred during November, December and January 2.  Rather remarkably, POWV may be transmitted within 15 minutes of a tick bite in contrast to the agent of Lyme disease which typically takes at least 48 hours2!

The most common clinical presentation is a febrile illness associated with encephalitis, meningoencephalitis or aseptic meningitis.  Seizures, focal deficits, aphasia, and dysarthria have been reported2. Typically, cerebrospinal fluid shows lymphocytic pleocytosis, normal glucose, and normal or mildly elevated protein.  Electroencephalography (EEG) reveals generalized slow wave activity and MRI of the brain may suggest microvascular ischemia or demyelinating disease in the parietal or temporal lobes. Collectively, the clinical presentation may resemble those seen in herpes simplex virus encephalitis. 

POWV disease carries 10% mortality with severe neurological sequelae in 50% of survivors4.  Despite lack of effective treatment, POWV should be considered in the differential diagnosis of acute encephalitis in endemic areas.

 

References

  1. CDC. https://www.cdc.gov/powassan/statistics.html  
  2. El Khoury MC, Camargo JF, White JL. Potential role of deer tick virus in Powassan encephalitis cases in Lyme disease-endemic areas of New York, USA. Emerg Infect Dis 2013;19:1928-33.
  3. CDC. www.cdc.gov/powassan/clincallabeval.html
  4. Hermance ME, Thanagamai S. Tick saliva enhances Powassan virus transmission to the host, influencing its dissemination and the course of disease. J Virol 2015; 89:7852-60.
Should I consider Powassan virus (POWV) in my patient with acute encephalitis?