n. flushing of the skin due to dilatation of the blood capillaries in the dermis. It may be physiological or a sign of inflammation or infection. Erythema nodosum is characterized by tender bruiselike swellings on the shins and is often associated with streptococcal infection. In erythema multiforme the eruption, which can take various forms, is characterized by so-called ‘target lesions’ that may be recurrent and follow herpes simplex infection (especially in children) or medications (especially in adults). Erythema ab igne is a reticular pigmented rash on the lower legs or elsewhere caused by persistent exposure to radiant heat. Erythema infectiosum (fifth disease, slapped cheek syndrome) is a common benign infectious disease of children caused by erythrovirus (human *parvovirus B19). It is characterized by fever and a rash, first on the cheeks and later on the trunk and extremities, that disappears after several days. Erythema toxicum neonatorum (neonatal urticaria) is a common self-limiting asymptomatic rash appearing in up to half of newborns, usually 2–5 days after birth. It is characterized by small erythematous papules and pustules surrounded by a diffuse blotchy erythematous halo. The eruption typically resolves within the first two weeks of life. See also palmar erythema. —erythematous adj.... erythema
the accumulation of fluid in fetal tissues or body cavities. This may take the form of a *cystic hygroma. In its most severe form, excessive fluid collects in the peritoneal cavity (see ascites), the pleural and pericardial cavities, and the soft tissues (see oedema). Hydrops may occur at any stage of gestation but is not usually seen until 16–18 weeks; the earlier it presents, the worse the prognosis. There are several causes of hydrops, one of which is severe anaemia associated with rhesus factor incompatibility (see haemolytic disease of the newborn). Other (nonimmune) causes include congenital heart defects, fetal arrhythmias, chromosomal abnormalities, and fetal infection with human *parvovirus B19 (erythrovirus). Treatment before birth with intrauterine blood transfusions to the fetus may be undertaken in specialized fetal medicine units; without treatment the mortality is high. Prenatal ultrasound scanning enables early recognition of hydrops fetalis and has been enhanced with the introduction of MCA Doppler (see Doppler ultrasound).... hydrops fetalis
n. any member of a genus of small DNA-containing viruses. Human parvovirus B19 (now known as erythrovirus) is the only member to cause disease in humans. It destroys red blood cells and is responsible for severe anaemia in patients with sickle-cell disease. Infection during pregnancy may adversely affect the fetus, resulting in *hydrops fetalis. The virus is also the causative agent of the childhood infection *erythema infectiosum.... parvovirus
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