Pediatric Rocky Mountain Spotted Fever Workup
- Author: Nicholas John Bennett, MBBCh, PhD, MA(Cantab), FAAP; Chief Editor: Russell W Steele, MD more...
Laboratory findings may be nonspecific in Rocky Mountain spotted fever (RMSF). On the complete blood count, the total leukocyte count may be normal, elevated, or decreased but usually shows a left shift.
Mild anemia and thrombocytopenia of less than 150 × 109/L (< 150 × 103/µL) occur in approximately one third of patients. Severe thrombocytopenia of less than 20 × 109/L (< 20 × 103/µL) occurs in approximately 10% of patients.
On a comprehensive metabolic panel, the following may be noted:
Hyponatremia (serum sodium < 130 mEq/L) in 20% of patients
The serum alanine aminotransferase level is usually increased
Serum albumin values may be low
The blood urea nitrogen (BUN) level is increased
Results of cerebrospinal fluid (CSF) analysis are generally normal. However, mild pleocytosis may be present, and approximately 50% of patients have a predominance of polymorphonuclear cells. An elevated CSF protein level may also be observed.
Serologic assays to detect anti– R rickettsii immunoglobulin G (IgG) antibodies are usually performed for definitive diagnosis. Testing of acute-phase and convalescent-phase sera is recommended to demonstrate a 4-fold or higher increase in the titer.
Enzyme immunoassays (EIAs) and immunoglobulin M (IgM) antibody-capture immunoassays are new serologic tests that potentially allow for early diagnosis.
In research laboratories, isolation of rickettsiae from tissues or direct detection of rickettsiae in tissues by means of direct immunofluorescence is used to confirm the diagnosis. Polymerase chain reaction tests have been developed but are not widely available.
CT imaging is typically normal, whereas MRI seems more sensitive at revealing abnormalities. Published findings include diffuse edema, effacement of the sulci, arterial infarctions, prominent perivascular spaces, and enhancement of the meninges (ie typical findings of meningoencephalitis). In 2 recent pediatric cases of Rocky Mountain spotted fever (RMSF) with encephalitis, scattered nonenhancing punctate lesions were described throughout the cerebral white matter, visible on T2- and diffusion-weighted MRI.[9, 10]
McQuiston JH, Guerra MA, Watts MR, Lawaczeck E, Levy C, Nicholson WL, et al. Evidence of exposure to spotted fever group rickettsiae among Arizona dogs outside a previously documented outbreak area. Zoonoses Public Health. 2011 Mar. 58(2):85-92. [Medline].
Chapman AS, Bakken JS, Folk SM, et al. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain spotted fever, ehrlichioses, and anaplasmosis--United States: a practical guide for physicians and other health-care and public health professionals. MMWR Recomm Rep. 2006 Mar 31. 55(RR-4):1-27. [Medline]. [Full Text].
Openshaw JJ, Swerdlow DL, Krebs JW, et al. Rocky mountain spotted fever in the United States, 2000-2007: interpreting contemporary increases in incidence. Am J Trop Med Hyg. 2010 Jul. 83(1):174-82. [Medline]. [Full Text].
Centers for Disease Control and Prevention. Rocky Mountain Spotted Fever - Statistics and Epidemiology. Available at http://www.cdc.gov/rmsf/stats/. Accessed: January 27, 2013.
Holman RC, McQuiston JH, Haberling DL, Cheek JE. Increasing incidence of Rocky Mountain spotted fever among the American Indian population in the United States. Am J Trop Med Hyg. 2009 Apr. 80(4):601-5. [Medline].
Adjemian JZ, Krebs J, Mandel E, McQuiston J. Spatial clustering by disease severity among reported Rocky Mountain spotted fever cases in the United States, 2001-2005. Am J Trop Med Hyg. 2009 Jan. 80(1):72-7. [Medline].
Folkema AM, Holman RC, McQuiston JH, Cheek JE. Trends in clinical diagnoses of Rocky Mountain spotted fever among American Indians, 2001-2008. Am J Trop Med Hyg. 2012 Jan. 86(1):152-8. [Medline]. [Full Text].
McQuiston JH, Wiedeman C, Singleton J, Carpenter LR, McElroy K, Mosites E, et al. Inadequacy of IgM antibody tests for diagnosis of Rocky Mountain Spotted Fever. Am J Trop Med Hyg. 2014 Oct. 91 (4):767-70. [Medline].
Maller VG, Agarwal AK, Choudhary AK. Diffusion imaging findings in Rocky Mountain spotted fever encephalitis: a case report. Emerg Radiol. 2012 Jan. 19(1):79-81. [Medline].
Crapp S, Harrar D, Strother M, Wushensky C, Pruthi S. Rocky Mountain spotted fever: 'starry sky' appearance with diffusion-weighted imaging in a child. Pediatr Radiol. 2012 Apr. 42(4):499-502. [Medline].
Centers for Disease Control and Prevention. Rocky Mountain Spotted Fever. Available at http://www.cdc.gov/rmsf/symptoms/index.html#treatment. Accessed: July 22, 2011.
Todd SR, Dahlgren FS, Traeger MS, Beltrán-Aguilar ED, Marianos DW, Hamilton C, et al. No visible dental staining in children treated with doxycycline for suspected Rocky Mountain Spotted Fever. J Pediatr. 2015 May. 166 (5):1246-51. [Medline].
|Organism||Disease or Presentation||Geographic Location|
|Rickettsia rickettsii||Rocky Mountain spotted fever||North, Central and South America|
|Rickettsia conorii||Mediterranean spotted fever, boutonneuse fever, Israeli spotted fever, Astrakhan fever, Indian tick typhus||Europe, Asia, Africa, India, Israel, Sicily, Russia, Europe, Asia, Africa, India, Israel, Sicily, Russia|
|Rickettsia sibirica||Siberian tick typhus, North Asian tick typhus||Siberia, People's Republic of China, Mongolia, Europe|
|Rickettsia australis||Queensland tick typhus||Australia|
|Rickettsia honei||Flinders Island spotted fever, Thai tick typhus||Australia, South Eastern Asia|
|Rickettsia africae||African tick-bite fever||Sub Saharan Africa, Caribbean|
|Rickettsia japonica||Japanese or Oriental spotted fever||Japan|
|Rickettsia felis||Cat flea rickettsiosis, flea borne typhus||Worldwide|
|Rickettsia slovaca||Necrosis, erythema, lymphadenopathy||Europe|
|Rickettsia heilongjaiangensis||Mild spotted fever||China, Asian region of Russia|
|Rickettsia parkeri||Mild spotted fever||US|