A 28-year-old African American man is given prophylactic medications and vaccinations before a business trip to Africa. Five days later, he comes to the emergency department due to jaundice and dark urine. Laboratory results are as follows: A peripheral smear shows red blood cells with dark inclusions when stained with supravital stain. This patient's condition most likely has which of the following inheritance patterns?

Question

A 28-year-old African American man is given prophylactic medications and vaccinations before a business trip to Africa.  Five days later, he comes to the emergency department due to jaundice and dark urine.  Laboratory results are as follows:  A peripheral smear shows red blood cells with dark inclusions when stained with supravital stain.  This patient's condition most likely has which of the following inheritance patterns?

Quizplus · Accepted Answer

This patient has the classic history of hemolytic anemia due to medication-induced oxidative stress. The antimalarial drugs usually prescribed for travelers to affected regions (eg, certain parts of Africa) are notorious instigators of hemolysis in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Laboratory studies reflect intravascular and extravascular hemolysis with anemia, reticulocytosis, indirect hyperbilirubinemia, and low haptoglobin (due to the removal of free hemoglobin-haptoglobin complexes). Peripheral blood smear shows red blood cells with Heinz bodies, dark, intracellular inclusions that stain with supravital stain and represent hemoglobin that has denatured/precipitated from oxidative stress. Heinz bodies are strongly associated with G6PD deficiency and other unstable hemoglobinopathies. The expression of G6PD is determined by a gene located on the X chromosome and has X-linked recessive inheritance. Among individuals with the mutation, males are affected and females are generally carriers. (Choices A and B) Most structural abnormalities follow an autosomal dominant pattern, whereas most enzyme deficiencies follow an autosomal recessive pattern. For example, hereditary spherocytosis is most often autosomal dominant. (Choice C) In a zygote, all of the mitochondria are inherited from the mother. These mitochondria have a small genome, so defects are transmitted only from mothers but affect offspring of both genders. Mitochondrial diseases generally affect oxidative phosphorylation (eg, Leber hereditary optic neuropathy). (Choice D) In X-linked dominant inheritance, there is 100% risk to female offspring of an affected male. For example, vitamin D-resistant rickets has an X-linked dominant inheritance pattern. Educational objective: Glucose-6-phosphate dehydrogenase deficiency has an X-linked recessive inheritance. Hereditary spherocytosis follows an autosomal dominant inheritance pattern.

A 28-Year-Old African American Man Is Given Prophylactic Medications and Vaccinations