Erythematous Macules and Papules

Approach

Differentiating rashes due to infection from other common cutaneous eruptions, particularly adverse drug eruptions, can be difficult. Recognizing the differences in presentation and using proper terminology for erythematous exanthems are the initial steps.

The commonly used (and often overused) term maculopapular describes a rash that has components of both macules (discolored spots or patches of various shapes and sizes that are neither raised nor depressed) and papules (small elevated areas that are solid and circumscribed) at some time during the course of the disease. Morbilliform (i.e., measles-like) is used to describe uniform lesions that have coalesced. Scarlatiniform is used when the exanthem resembles scarlet fever (i.e., has a sandpaper feel and is confluent in the flexural areas). If lesions are generalized but remain discrete, the term rubelliform may be used.

Secondary characteristics should be added to further describe the exanthem; annular, lacy, reticulated, evanescent, urticarial, petechial, and purpuric are useful descriptors. Color is described in shades. For example, erythema can range from faint pink to violaceous red.

Many of the classic exanthems, such as measles, rubella, and erythema infectiosum, are associated with macules or papules on the skin. Differentiating common and uncommon causes of infectious rashes often is difficult because the patterns are not always unique to a specific infectious agent. Detailed and accurate history taking is vital to making a correct diagnosis ( Box 68.1 ). The patient’s age and pre-existing conditions are important because many infectious rashes occur predominantly within a specific age range or in the context of another illness.

Etiologic Agents, Epidemiology, and Pathogenesis

Macular and papular exanthems can result from numerous infectious causes. An extensive list of viral and nonviral causes is shown in Box 68.2 . In children, enteroviruses are by far the most common cause of morbilliform rash with febrile illness, especially for those younger than 1 year of age. Coxsackie A6, an enterovirus associated with severe hand-foot-mouth disease, often presents with a generalized exanthem ( Fig. 68.1 ) with or without classic vesicular lesions. Enteroviruses have a marked seasonality, with an increase in prevalence in the summer and a large peak in August and autumn. Parvovirus B19, the etiologic agent of erythema infectiosum, is the maculopapular rash most commonly identified in children 4 through 10 years of age. The exanthem is typified by bright red macules on the cheeks that spare the nasolabial folds ( Fig. 68.2 ), followed by the development of reticulated lacy pink macules and thin papules on the extremities that can persist for up to 3 weeks. Measles occurs as sporadic imported cases or in high-profile outbreaks in the United States and is still prevalent worldwide. Measles is characterized by the classic morbilliform rash with cranial-to-caudal progression and is accompanied by fever and the three Cs: cough, conjunctivitis, and coryza. Severe SARS-CoV-2, the etiologic agent of novel coronavirus disease-19 (COVID-19), has been associated with various skin lesions, most commonly a maculopapular rash. Other cutaneous manifestations of COVID-19 have also been described, including acral chilblain-like lesions. While these dermatologic findings appear to be less common in pediatric patients, rash has been noted to be a common presenting symptom of SARS-CoV-2-related multisystem inflammatory syndrome in children (MIS-C) ( Fig. 68.3 ). ^,