A nurse calls you to tell you that an infant has a rash. A rash is any change of skin that affects its color, appearance, or texture. Although the majority of rashes in newborns are benign and require no treatment, certain rashes require a workup and intervention.
What are the characteristics of the rash? Morphology of the lesion aids differential diagnosis. Is it macular (flat lesion <1 cm), papular (raised up to 1 cm), nodular (raised up to 2 cm), vesicular (raised, <1 cm, filled with clear fluid), bullous (raised, >1 cm, with clear fluid), or pustular (raised with purulent fluid)?
Are there petechiae (tiny pinpoint red dots from broken blood vessels), purpura (large, flat area of blood under tissue), or ecchymosis (very large bruised area)? All can result from intradermal bleeding and need to be differentiated from erythema (redness of the skin). With erythema, the redness is cleared when pressed and returns when you release. With pressure, petechiae, purpura, and ecchymosis do not blanch. Petechiae on the lower body after a breech delivery or upper body with a vertex presentation can be normal. If widespread, petechiae are considered abnormal. Petechiae and purpura can signify thrombocytopenia and require a workup.
Is there a history of a congenital infection? Obtain a thorough maternal history. TORCH (toxoplasmosis, other, rubella, cytomegalovirus, herpes simplex virus) infections are known to cause rashes. The “blueberry muffin baby” has widespread purpura and papules and can be seen in rubella (the term was first used to describe infants infected with rubella in the epidemic of 1960), cytomegalovirus (CMV; most common viral infection), and syphilis. Cutaneous extramedullary hematopoiesis causes the blueberry muffin rash. The blueberry muffin rash has historically been associated with congenital viral infections but can also be seen in blood disorders (hemolytic disease of the newborn, twin-to-twin transfusion, hereditary spherocytosis), vascular disorders (multiple hemangiomas, blue rubber bleb nevus, multiple glomangiomas, multifocal lymphangioendotheliomatosis), and malignancies (neuroblastoma, congenital leukemia cutis, Langerhans cell histiocytosis, and congenital rhabdomyosarcoma). See Chapter 141 and disease-specific chapters.
Is the infant ill appearing? A well infant with a rash suggests a benign rash. A febrile or ill-appearing infant with a rash requires a thorough workup to search specifically for an infectious cause.
What medications did the mother receive during pregnancy and delivery? Is the mother breast-feeding and taking any medications? Medications are a rare cause of rash in infants. Methimazole, an antithyroid medication, has been associated with aplasia cutis, a localized absence of skin on the scalp.
Does the skin lesion make you think of a genetic disorder? Skin lesions can be associated with genetic syndromes. Blisters: epidermolysis bullosa. Brown, flat patches: Neurofibromatosis. Cutis marmorata: Cornelia de Lange syndrome and in trisomies 18 (Edward syndrome) and 21 (Down syndrome). Deficient hair and nails: ectodermal dysplasias. Scaly, thick skin: ichthyoses. Thin, fragile skin: collagen disorders and hypoplasia of the dermis. Unformed skin: ...
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