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| CASE REPORT |
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| Year : 2020 | Volume
: 17
| Issue : 3 | Page : 86-88 |
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An interesting story of intravascular hemolysis but normal haptoglobin and bilirubin levels
Kriti Chauhan1, Nikhil Shandilya2
1 Department of Pathology, Polo Labs, Ivy Hospital, Panchkula, Haryana, India
2 Department of Critical Care, Alchemist Group of Hospitals, Panchkula, Haryana, India
| Date of Submission | 22-Nov-2019 |
| Date of Acceptance | 13-Apr-2020 |
| Date of Web Publication | 04-Jul-2020 |
Correspondence Address:
Dr. Kriti Chauhan
Polo Labs, Ivy Hospital, MDC, Sector 5C, Panchkula - 134 112, Haryana
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jcls.jcls_76_19
Multiple bee stings are associated with intravascular hemolysis (IVH), rhabdomyolysis, hypotension, renal tubule injury, and all causing acute kidney injury. Evidence in support of hemolysis includes anemia, hyperbilirubinemia, hemoglobinemia, hemoglobinuria, low haptoglobin (Hp) levels, elevated lactate dehydrogenase, and Coomb's test (if antibody mediated). However, under certain circumstances, hemoglobinemia and hemoglobinuria may be the only evidence of IVH depending on the etiological factors in association with the environment inside the body. Bee venom is known to have deleterious actions on different tissue types (neurotoxin, muscle paralytic, hematotoxic, epithelial damage, etc.). Altogether, they determine the outcome and presentation. Apart from this, there are several conditions that determine the binding of oxygen and Hp to hemoglobin (Hb). Arterial blood gases (ABGs) play a very important role in this. Hence, it is important for the pathologists to have an understanding of ABG as well to know how even simple tests (Hb, bilirubin, and Hp) can get affected by them. We describe one such occurrence in a patient with multiple hornet bee stings and formulate the likely causes and pathogenesis.
Keywords: Bee sting, bilirubin, haptoglobin, intravascular hemolysis
How to cite this article:
Chauhan K, Shandilya N. An interesting story of intravascular hemolysis but normal haptoglobin and bilirubin levels. J Clin Sci 2020;17:86-8 |
| Introduction | |  |
Hemolysis means the destruction of red blood cells (RBCs) within the body before they have finished their normal life span. They are prematurely removed from the circulation by macrophages in spleen, liver, and bone marrow, where they are phagocytosed. This is called as extravascular hemolysis and is always occurring in hemolytic anemia. However, in some circumstances, there is concurrent intravascular hemolysis (IVH) going on, in which RBCs rupture to release hemoglobin (Hb) in the blood vessels. There are multiple causes of IVH, such as immune mediated (autoimmune), infections (erythroparasites such as babesia and malaria), oxidant injury, enzyme deficiencies, and RBC structural defects.[1] There have been reports of bee stings, spider bites, and snake venoms as well, causing IVH (due to phospholipases in the venom).[2]
| Case Report | | |
A 44-year-old male presented with complaints of difficulty in breathing and “cola-colored” urine. He gave a history of multiple hornet bee stings, 2 days back for which he was managed in a nearby hospital with intravenous fluids and antibiotics. Subsequently, he noticed reddish discoloration of urine following which he was referred to a higher center for management. His laboratory investigations revealed anemia (Hb: 10.3 g/dl), elevated liver enzymes (serum glutamic oxaloacetic transaminase: 781U/L, serum glutamate-pyruvate transaminase: 461U/L), increased urea and creatinine levels (urea: 130 mg/dl, creatinine: 2.79 mg/dl), and hypoproteinemia (protein: 5.7 g/dl). The plasma and serum samples obtained after centrifugation showed marked reddish discoloration owing to hemoglobinemia. The urine sample was red in color and yielded a cola-colored supernatant on centrifugation, consistent with hemoglobinuria, and ruling out hematuria. Dipstick examination revealed 3+ proteinuria and 4+ blood but no RBCs under the microscope. Peripheral smear examination showed reduced red cell density and a dimorphic picture of both microcytic and macrocytic RBCs with marked polychromasia and reticulocytosis (5.2%, corrected for anemia). Leucocyte count was elevated with neutrophilia. Platelets were adequate. No evidence of fragmented RBCs, schistocytes, or other abnormal cells was seen. All these findings favored regenerative anemia. In this case, the cause was IVH induced by the venom in a bee sting. An unusual finding was that despite hemoglobinemia and hemoglobinuria, the total and unconjugated levels of bilirubin were within normal limits. Futhermore, in contrast to the normal phenomenon, in which haptoglobin (Hp) binds and scavenges-free Hb, causing a marked reduction in Hp levels, Hp was within the normal range in this case (79.80, N: 30–200 mg/dl). This implies that Hp was not able to bind free Hb intravascularly. Arterial blood gases (ABGs) revealed a ph of 7.5, pCO2 of 29.06 mmHg, pO2 of 61.80 mmHg, and SO2 of 94.8%, which means the patient was in a state of respiratory alkalosis which causes a shift the oxygen dissociation curve (ODC) to the left. This means less oxygen is released to the tissues and more oxygen is bound to Hb in the lungs. In other words, at the tissue level, the majority of Hb is in deoxy form, and it has a strong affinity for O2. [Figure 1] shows the possible sequence of events in the patient in an algorithmic pattern, Lactate dehydrogenase was mildly elevated (598.6, N: 114-240 IU/L). Creatinine kinase levels were normal ruling out rhabdomyolysis, which can present with a similar picture (183.0, N: 25-200 IU/L). Direct and indirect Coomb's test was negative. The patient was started on alkaline diuresis, following which his condition improved, but the kidneys remained affected.{Figure 1}
| Discussion | | |
Bee stings have several venomous substances such as melittin (hemolytic, vasoactive properties), phospholipase A and B (cell membrane lytic action), apamin (neurotoxin), hyaluronidase, and histamine. Phospholipase and melittin are the most abundant of these and act as potent neuromuscular blocking agents causing respiratory paralysis.[3] Some toxins also cause injury to the vascular endothelium resulting in increased vascular permeability, which causes leakage of Hb into plasma and an exudative type of pleural effusion. This aggravates an already occurring respiratory distress and leads to a state of respiratory alkalosis. Alkalosis causes shift of the ODC to the left, which leaves most of the Hb in the unsaturated (deoxy) form at the tissue level, as also observed in our case.[4] Hb in the deoxygenated state does not bind to Hp because the conformation of deoxygenated Hb dimers does not promote Hp binding.[5] Hence, there is no scavenging of Hb–Hp complexes. Hp is synthesized mainly by hepatocytes and consists of both alpha and beta subunits linked by disulfide bonds-forming dimers. Three genotypes of Hp are found in humans: Hp1-1, Hp2-1, and Hp2-2. Their properties vary in binding strength, anti-oxidative ability, and rate of clearance. In some studies, it has been found that the binding strength is greatest with Hp1-1 and weakest with Hp2-2, but Hp-2 genotypes can bind a larger number of Hb dimers, while others state that since the Hp β chain is the same for all Hp proteins, the affinity of Hp 1-1 for Hb does not differ from that of Hp 2-2. However, all agree that heme iron associated with the Hp2-2/Hb complex is more redox active than other Hp-type complexes.[6],[7] There might be a possibility of the Hp2 genotype being the predominant form in this case. Free Hb in plasma and tissues reacts with nitric oxide (NO) and other physiologic oxidants resulting in NO (vasodilator) depletion and accumulation of Hb-Fe+3 within tissues, which promotes hemin release and transfer of hemin to other proteins/lipids resulting in free radical injury and tissue damage as evidenced by elevated transaminases and urea/creatinine levels in our case.[8] The kidney is the biggest victim of IVH because unbound Hb is filtered into urine, causing hemoglobinuria. This free Hb scavanges free “NO”, which is an important vasodilator of the renal medulla resulting in renal ischemia and acute tubular injury or necrosis. Second, Hb that is filtered into urine is taken up by the renal tubules where free iron is liberated, causing free radical injury.[9],[10] To conclude, it can be said that decreased Hp levels and hyperbilirubinemia may not always be seen in IVH. In this case, the hornet bee sting had venomous substances that could cause respiratory muscle paralysis and endothelial injury apart from hemolysis because of which most of the Hb could not bind Hp. The potential causes may be translocation of Hb into the extravascular space owing to endothelial injury where there is no Hp to bind, the predominance of deoxy-Hb, and abundance of Hp2-2 genotype. Hemoglobinemia, hemoglobinuria, reticulocytosis, and peripheral smear findings were the only positive findings in favor of IVH. Alkaline diuresis and optimal hydration are the keys to treatment so that most of the toxins and Hb are flushed out of the system.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Acknowledgment
The author is extremely thankful to the clinicians for providing the clinical perspective in the case analysis and in the interpretation of ABG.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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