Oral lesions called Koplik spots may develop 2-3 days after symptoms begin and prior to the generalized cutaneous eruption. Look for minute, white papules, which may have a central bluish-white portion, usually opposite the second molars on the buccal mucosa. They can also appear red. Bluish-gray or white papules can also be seen on the tonsils. These resolve as the morbilliform rash appears. This enanthem is considered pathognomonic for measles.
The exanthem consists of erythematous macules and papules beginning at the forehead and behind the ears, eventually spreading in a cephalocaudal fashion down the neck, upper extremities, trunk, and lower extremities. Confluent lesions can occur on the face. The rash typically peaks for 3-4 days, then begins to fade at day 5 in the same manner in which it appeared. Desquamation typically occurs after approximately 1 week. Thrombocytopenia, with resultant purpuric lesions, may complicate measles.
Variant: Atypical measles (in those receiving formalin-inactivated measles vaccine between 1963 and 1968 or in whom immunization has failed) will spread from the extremities inward. Petechiae, purpura, vesicles, or acral edema can occur. Cough and conjunctivitis are not as marked as in classic measles.
Impact of skin color on clinical presentation: In darker skin colors, erythema may be subtler or may appear more violaceous or hyperpigmented. Applying brief gentle pressure with a fingertip or microscope slide to blanch involved skin may accentuate subtle erythema as the pressure is withdrawn. Use of a bright light may further illuminate any subtle color changes present. In lighter skin colors, the active border may be any shade of pink or red. In skin of intermediate color, erythema may be deep red, maroon, or violaceous. Postinflammatory hyperpigmentation is more prominent and lasts longer in darker skin colors.
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