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A child with respiratory distress and chocolate brown arterial blood

 Department of Paediatrics, Pondicherry Institute of Medical Sciences, Puducherry, India

Date of Submission20-Oct-2022
Date of Decision01-Dec-2022
Date of Acceptance05-Dec-2022
Date of Web Publication02-Mar-2023

Correspondence Address:
Priya Jose,
Department of Pediatrics, Pondicherry Institute of Medical Sciences, Kalapet, Puducherry - 605 014
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcrsm.jcrsm_87_22


Methemoglobinemia is a hemoglobinopathy that occurs when the heme is oxidated. Ferric iron in oxidized heme cannot bind and transport oxygen. Hence, when the concentration exceeds 15%, symptoms start with cyanosis, distress, and tachypnea, and may progress to seizure, unconsciousness, and even death as the concentration increases. Congenital methemoglobinemia is rare and often clinically missed but responds well with medications. Here, the case of a 12-year-old girl with respiratory distress and no cyanosis is being reported. The diagnosis was made based on a chocolate brown-colored arterial blood sample taken for analysis. The importance of considering this condition as a differential diagnosis in a case of respiratory distress of unknown etiology is being discussed here.

Keywords: Arterial blood, ascorbic acid, congenital methemoglobinemia, dyspnea

How to cite this URL:
Amalraj FJ, Jose P, Ponnarmeni S, Kumar Kommu PP. A child with respiratory distress and chocolate brown arterial blood. J Curr Res Sci Med [Epub ahead of print] [cited 2023 Mar 31]. Available from: https://www.jcrsmed.org/preprintarticle.asp?id=370929

  Introduction Top

Methemoglobin (MetHb) is found in the serum of every human being, but its concentration in normal human serum is <1%.[1] Methemoglobinemia is a rare hemoglobinopathy that occurs when oxidation of heme occurs from Fe2+ to Fe3+.[2] MetHb cannot carry oxygen to tissue; hence it leads to hypoxia and cyanosis. These symptoms usually occur if the concentration of MetHb exceeds 15%.[3] The common presentation of methemoglobinemia is central and peripheral cyanosis. However, this patient presented with an infectious course of pyrexia of unknown origin, and respiratory distress, which is an atypical presentation. The incidence of methemoglobinemia is not well reported, and thus there is a necessity of reporting all the diagnosed cases at the earliest. The importance of considering this condition as a differential diagnosis in a case of respiratory distress of unknown etiology has been highlighted in this report.

  Case Report Top

A 12-year-old girl, the third born of a 3rd consanguineous marriage, who had a smooth transition at birth, who was developmentally normal, immunized for age with no significant past history, was brought for a consultation to our hospital after multiple consultations at different hospitals with a history of recurrent low-grade fever and lethargy of about 3-month duration. She had developed a cough and New York Heart Association grade II dyspnea 3 days prior to the consultation. She has received only symptomatic management for the last 3 months. There was no documented high temperature in those 3 months.

On examination, she was alert and afebrile but dyspneic. No pallor or cyanosis was present. No rash or bite marks were seen.

She was hemodynamically stable with good perfusion. However, she had tachypnea with a respiratory rate of 40 breaths/min, and oxygen saturation of 90% at room temperature. There were no intercostal or subcostal retractions. She was started on 15 L of oxygen with a nonrebreathing mask in the intensive unit. Her blood sugar was 102 mg/dL. Pupils – 2 mm, equally reacting to light. On auscultation, there was bilaterally symmetrical air entry, normal vesicular breath sounds, and no crepitations or rhonchi. Sepsis screening was negative. Hemoglobin was 8.1 gm%. The liver function tests were normal.

The child was started on parenteral antibiotics after taking blood for routine investigations. The blood culture was sterile after 48 h of incubation. Chest X-ray was normal. Different saturation probes were utilized to rule out instrument errors. The severity of hypoxia was disproportionate to the severity of respiratory distress. Electrocardiogram and echocardiogram were done to check for cardiac dysfunction, and no abnormalities were detected. Because of disproportionate hypoxemia, arterial blood gas (ABG) analysis was done. The arterial blood was chocolate brown [Figure 1] in color, and methemoglobinemia was suspected. ABG showed hyperoxia, respiratory alkalosis, and metabolic acidosis. CO-oximeter testing was done at a central institute due to the lack of facility at our center and showed PCO2: 32.9 mmHg, PO2: 121.2 mmHg, pH: 7.410, OxyHb: 90%, and MetHb: 10% The CO-oximeter readings confirmed methemoglobinemia. We ruled out acquired methemoglobinemia clinically due to the absence of exposure to toxins and drugs causing this condition. Congenital methemoglobinemia was suspected as her parents had a third-degree consanguineous marriage. We started her on oral ascorbic acid (15mg/kg/day), and she improved dramatically. She was weaned off oxygen therapy and oxygen saturation remained adequate. Hemoglobin was normal for parents and siblings. Genetic testing could not be done because of financial constraints. The child is healthy and asymptomatic on follow-up.
Figure 1: Chocolate brown blood collected for blood gas analysis

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  Discussion Top

Normally, hemoglobin contains iron molecules in the ferrous state (Fe2+) which is responsible for oxygen transport. Due to various reasons such as oxidative stress, exposure to toxins, or genetic causes, ferrous ion becomes oxidized to ferric ion (Fe3+). This form does not bind with oxygen instead binds to a water molecule to give MetHb.[2]

Methemoglobinemia can be either acquired or congenital. Acquired methemoglobinemia is quite common and has been extensively discussed in the literature, but the incidence of congenital methemoglobinemia is rare.[4] Congenital methemoglobinemia is of two types. Type I is due to nicotinamide adenine dinucleotide-cytb5 reductase enzyme (CYB5R) functional deficiency in erythrocytes and is more common, while Type II is due to deficiency of CYB5R in all the cells and is rare with low life expectancy.[5]

Children present with a wide range of symptoms. The majority of the cases present with cyanosis when the concentration of MetHb exceeds 15%. Tachypnea and syncope can occur between 30% and 50%, and the possibility of seizures, metabolic acidosis, and coma between 50% and 70%, and if the concentration is >70% can lead to death.[5] There are hardly any reported cases of being symptomatic with MetHb of 10%.

In congenital methemoglobinemia, though a methemoglobin level of 20% indicates enzyme deficiency, patients develop physiological compensatory mechanisms and will be able to tolerate up to 40% of the MetHb level without any significant symptoms[6] unlike the current case. The physiological compensatory mechanisms would not have developed in this child and so respiratory distress started developing with a MetHb level of 10%.

In this case, the patient had respiratory distress even at a 10% MetHb level and did not have the classical presentation of cyanosis. Due to an atypical presentation, the diagnosis of methemoglobinemia was not considered. The investigations and multiple hospital visits could have been optimized if this differential diagnosis was considered earlier on. This could have lessened the parents' anxiety.

Methylene blue at 1–2mg/kg over 5 min intravenously remains the mainstay of treatment. Since the HbMet was not >15%, oral ascorbic acid was prescribed, and the child improved drastically. There is sufficient literature available for treatment with intravenous ascorbic acids, but very scarce for oral management. A 4-year old cerebral palsy child who presented with cyanosis and was diagnosed with congenital methemoglobinemia was successfully treated with oral ascorbic acid.[7] A child with developmental delay who presented with cyanosis for 6 months, diagnosed as congenital methemoglobinemia, improved with a high dose of ascorbic acid.[8]

  Conclusion Top

Congenital methemoglobinemia should be considered a differential diagnosis though rare in cases of respiratory distress and lethargy without fever. Although it is not a classical presentation of the disease, detecting the condition early can be potentially lifesaving.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient's mother has given her consent for her daughter's clinical information to be reported in the journal. The patient's mother understands that her daughter's name and initials will not be published, and due efforts will be made to conceal her daughter's identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Alanazi MQ. Drugs may be induced methemoglobinemia. J Hematol Thrombo Dis 2017;5:1-5.  Back to cited text no. 1
Kaminecki I, Huang D. Methemoglobinemia. Pediatr Rev 2021;42:164-6.  Back to cited text no. 2
Saadia A, Haroon Yusaf M, Qureshi A, Mumtaz A. Congenital methemoglobinemia. Iran J Pathol 2012;7:135-8.  Back to cited text no. 3
Ara T, Haque QS, Afrose S. A rare case of congenital methemoglobinemia with secondary polycythemia-case report and literature review. Haematol J Bangladesh 2019;3:20-3.  Back to cited text no. 4
Viršilas E, Timukienė L, Liubšys A. Congenital methemoglobinemia: Rare presentation of cyanosis in newborns. Clin Pract 2019;9:1188.  Back to cited text no. 5
Rechetzki KF, Henneberg R, da Silva PH, do Nascimento AJ. Reference values for methemoglobin concentrations in children. Rev Bras Hematol Hemoter 2012;34:14-6.  Back to cited text no. 6
Gokalp S, Unuvar E, Oguz F, Kilic A, Sidal M. A case with quadriparetic cerebral palsy and cyanosis: Congenital methemoglobinemia. Pediatr Neurol 2005;33:131-3.  Back to cited text no. 7
Nellicka S, John A, Abraham V. Congenital methemoglobinemia type 2. A rare case report. Pediatric Oncall J 2017;14:19.  Back to cited text no. 8


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