EXANTHEMATOUS FEVERS (Fever with Rash)

While rashes are seen in many febrile illnesses, term Exanthematous fevers is usually reserved for fevers consistently associated with skin eruptions during the usual clinical course.

Etiology: Skin lesions in infectious diseases may be due to: (a) direct inoculation, e.g. anthrax, (b) contagious spread from adjacent foci, e.g. herpes, (c) hematogenous spread, e.g. meningococci, (d) toxins, e.g. scarlet fever and (e) immune reactions, e.g. rheumatic fever. Most exanthematous fevers are viral in origin (Table 10.4), commonest being measles and varicella.

Diagnostic evaluation of exanthematous fevers depends on the epidemiological history of similar illnesses in the community, along with: (a) duration and severity of prodromal phase, (b) nature, distribution and duration of rash and (c) other associated features (Table 10.5). Non- infective causes of maculopapular or Vesiculobullous rashes (see Ch25.5 and 25.6) should also be excluded.

TABLE 10.3: Laboratory investigations in PUO

• Baseline (in all prolonged pyrexia)

- Complete hemogram

- Peripheral smear for immature cells, parasites

- Urine analysis

- X-ray chest and sinuses

- Tuberculin test

- Widal test

• Second-line (in all PUO cases)

- Biochemical: Liver function tests

- Microbial: Blood/urine cultures, AFB

- Cytological: CSF, bone marrow

- Serological:

#9830; Infections: HIV, leptospira, brucella

#9830; Others: ASO, ANA titers

- USG abdomen for deep-seated abscess

- Echocardiography for infective endocarditis

• Third-line (in selected cases)

- Whole body CT/MRI

- Radionuclide scans (bones, abdomen)

TABLE 10.4: Exanthematous fevers in India

• Viral:

- Common: Measles, varicella, enterovirus, dengue

- Others: IM, roseola, E. infectiosum, arboviruses

• Bacterial:

- Common: Enteric fever, meningococcemia

- Uncommon: Scarlet fever, anthrax

• Spirochetal: Leptospirosis

• Rickettsial: Typhus, rickettsial pox

• Mycoplasma: M. pneumoniae

• Protozoal: Toxoplasmosis

• Immunological: Rh. fever, JRA, Kawasaki disease

• Drug reactions: Stevens-Johnson syndrome

IM: Infectious mononucleosis; JRA: Juvenile rheumatoid arthritis

10.1.3