Health & Medical Neurological Conditions

What I've Learned About Infectious Diseases

´╗┐What I've Learned About Infectious Diseases
There are a number of neurological infections that present with a rash: meningococcemia, varicella zoster virus infections, enterovirus infections, and Rocky Mountain spotted fever are the most memorable. The rash of meningococcemia begins as a diffuse erythematous maculopapular rash resembling a viral exanthem. The rash begins on the trunk and lower extremities, and this is diagnostic. The lesions rapidly become petechial; lesions may also be found in the mucous membranes and conjunctiva and, occasionally, on the palms and soles. A petechial rash has been reported to occur in 15 to 62% of cases of meningococcal meningitis. Blood obtained from the cutaneous purpuric lesions may reveal the organism on Gram's stain.

The rash of a viral exanthem begins on the face and the trunk and then spreads to the extremities. Be highly suspicious of enteroviral meningitis in the patient that presents with fever, headache, stiff neck, and a maculopapular rash on the face and chest. A rash that is an adverse reaction to an antimicrobial agent typically begins on the face, then progresses to the chest and trunk, and then to the lower extremities. By the time the maculopapular eruption is present on the lower extremities, the rash on the face is nearly gone.

The rash of zoster is a vesicular eruption on an erythematous patch, typically in a cervical or thoracic dermatomal distribution, or in the distribution of the ophthalmic division of the trigeminal nerve. The combination of vesicular lesions in the external ear (zoster oticus) or hard palate with a facial nerve palsy is the Ramsay-Hunt syndrome. In the elderly and in immunocompromised patients, the rash may be disseminated. The rash of zoster is associated with pain and itching.

Rocky Mountain spotted fever is caused by the bacteria Rickettsia rickettsii. After an incubation period of 2 to 14 days from the time of a tick bite, the disease begins with fever, headache, nausea, and vomiting. The skin rash appears an average of 2 to 3 days after the onset of the illness, and typically begins on the ankles and wrists. The rash is initially a diffuse erythematous maculopapular rash that blanches with pressure. It progresses to a petechial rash, then to a purpuric rash, and if untreated to skin necrosis or gangrene. The color of the lesions of the rash change from bright red to very dark red, then from yellowish-green to black. From the wrists and ankles, the rash spreads distally and proximally within a matter of a few hours and involves the palms and soles.

Erythema migrans is the hallmark of Lyme borreliosis. Erythema migrans initially appears as a red macule, papule, or wheal at the site of a tick bite. The lesion expands over several days and then develops a targetlike appearance with central clearing. The lesion may continue to expand for weeks. As the infection becomes disseminated, there are multiple secondary annular lesions elsewhere in the skin, which are generally smaller and expand to a lesser degree.

The risk of transmission of Borrelia burgdorferi disease or Rickettsia rickettsii by a tick increases with the duration of attachment, and generally requires longer than 24 to 48 hours. The more engorged the tick is at the time it is identified and removed, the greater the likelihood that transmission of bacterial infection has occurred.

The first rule of the evaluation and treatment of a rash is "if it is wet, dry it; if it is dry, wet it; and -- for goodness sake -- never touch it." Primary syphilis is characterized by a painless chancre or ulcerated papule with a smooth, clean base and indurated borders. A generalized nonpruritic maculopapular rash that is most marked on the trunk, the extremities, and the palms and soles is characteristic of secondary syphilis. Mucous patches may also occur in the mouth or throat. Spinal fluid analysis is not recommended during the primary and secondary stages of syphilis as there is a 30 to 40% likelihood of CSF abnormalities that have never been shown to predict progression to neurological complications.

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