A 45-year-old man comes to the office for evaluation of fatigue that has been gradually increasing over the past 4 months. The patient has had difficulty keeping up with the labor involved with his job as a construction worker. Over the past 2 weeks, he has been unable to climb past the second floor of the building his company is renovating. The patient also has increasing shortness of breath with minor activities, such as lifting his toolbox out of the car. Review of systems reveals constipation and decreased concentration. Physical examination shows an overweight male with conjunctival pallor who has difficulty getting onto the examination table due to shortness of breath. Laboratory test results are as follows: Which of the following findings would most likely be seen on this patient's peripheral blood smear?

Question

A 45-year-old man comes to the office for evaluation of fatigue that has been gradually increasing over the past 4 months.  The patient has had difficulty keeping up with the labor involved with his job as a construction worker.  Over the past 2 weeks, he has been unable to climb past the second floor of the building his company is renovating.  The patient also has increasing shortness of breath with minor activities, such as lifting his toolbox out of the car.  Review of systems reveals constipation and decreased concentration.  Physical examination shows an overweight male with conjunctival pallor who has difficulty getting onto the examination table due to shortness of breath.  Laboratory test results are as follows:  Which of the following findings would most likely be seen on this patient's peripheral blood smear?

Quizplus · Accepted Answer

11ec160b_3af4_685b_9249_2f16495b17e6_MD0001_00 This patient has microcytic anemia, constipation, and mental status changes in the setting of construction work. The most likely diagnosis is lead poisoning. Lead is a soft, heavy metal used for manufacturing a wide range of items, including batteries, alloys, and ammunition. Individuals working in these industries and others (eg, construction, mining, smelting, chemical processing, recycling, spray painting, radiator repair) can be regularly exposed to lead. Lead inhibits the heme synthesis pathway (δ-aminolevulinate dehydratase and ferrochelatase), causing a microcytic, hypochromic anemia. Shortness of breath, particularly with exertion, occurs due to decreased oxygen delivery to peripheral tissues. Iron studies are normal unless co-existing iron deficiency is present as well. Basophilic stippling is frequently seen on peripheral blood smear. Inhibition of erythrocyte 5' nucleotidase by lead results in ribosome aggregation due to inability to degrade RNA, which is represented by coarse blue punctate dots in the cytoplasm of red blood cells (RBCs). Basophilic stippling is nonspecific and also seen in the thalassemias and myelodysplastic syndrome. Adult lead poisoning can also have the following manifestations: (Choice B) Heinz bodies are inclusions of denatured hemoglobin most commonly seen after oxidant stress in patients with glucose-6-phosphate dehydrogenase deficiency. (Choice C) Howell-Jolly bodies are nuclear DNA remnant inclusions in peripheral RBCs that are normally removed by the spleen during circulation. The presence of Howell-Jolly bodies indicates decreased or absent splenic function (eg, post-splenectomy). (Choice D) Ring sideroblasts are formed from precipitation of iron granules in developing erythrocytes due to defects in the heme synthesis pathway, including enzymatic inhibition induced by lead poisoning. Ring sideroblasts are seen in the bone marrow but not in the peripheral blood smear. (Choice E) Schistocytes are fragmented parts of RBCs formed from mechanical hemolysis via sheer force of blood flow. Hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, and disseminated intravascular coagulation all present with schistocytes. Educational objective: Lead poisoning in adults typically occurs through occupational exposure. Symptoms include colicky abdominal pain, constipation, lead lines on the gum, peripheral neuropathy, and anemia. Laboratory testing shows microcytic anemia with normal iron studies, and peripheral blood smear may reveal basophilic stippling. __________ References: Lead toxicity. (http://www.ncbi.nlm.nih.gov/pubmed/26644446) Basophilic stippling: a lead to the diagnosis. (http://www.ncbi.nlm.nih.gov/pubmed/22204026)

A 45-Year-Old Man Comes to the Office for Evaluation of Fatigue