Occult hereditary spherocytosis and human parvovirus infection.

The human parvovirus (HPV) is believed to be the causative agent of erythema infectiosum, or fifth disease. 1 Transient aplastic crisis linked to HPV infection has been described in several types of hemolytic anemias, congenital or acquired, such as sickle cell disease, thalassemia, autoimmune hemolytic anemias, and hereditary spherocytosis.2-8 In some instances, the underlying hemolytic anemia was not recognized until the patient developed transient aplastic crisis secondary to HPV infection. The B19 HPV has a propensity for the erythrocyte progenitor cells, to which it is cytotoxic.7 It is generally believed that a decrease in erythroblasts occurs in all patients on first contact with HPV B 19, but a crisis reveals itself only in patients whose erythrocytes have an inherent shortened life span (as in some hemolytic anemias). Hereditary spherocytosis is the most common hemolytic anemia in persons of Northern European extraction, occurring in 1 person in 5000.9 Although classically believed to be autosomal dominant in inheritance, 20 to 25 percent of patients with hereditary spherocytosis have normal parents, raising the question of mutation, incomplete penetrance, or recessive forms of the disease.9 The red cells of patients with hereditary spherocytosis have a membrane defect causing decreased cell surface area, leading to a spheroidal shape and osmotically fragile cells. Selectively trapped by the spleen, these cells have a shortened life span. The most common complication is gallbladder disease, with 55 to 85 percent of untreated patients eventually developing pigment gallstones. 10 Patients with hereditary spherocytosis may develop one of three types of crises, including (1) mild hemolytic crisis, with mild anemia, tran-