Her history includes treatment for a cold abscess in 2018, following which antitubercular treatment was initiated and completed. She was born of a nonconsanguineous marriage and had no history of similar illness reported in the family. She is married and has a 7-year-old son. She was not on any medication when she presented to our surgery OPD.
Following surgery consultation in our hospital, she underwent ultrasonography and fine-needle aspiration cytology. The findings were consistent with branchial cyst. Preanesthetic workup picked up a saturation gap (SPO2 was 84% in room air with ABG showing PO2 of 98.5 mmHg) for which a hematology consultation was done.
A detailed evaluation was done at the hematology department which revealed a history of dark brown-colored blood on cuts in the past. A history of giddiness and easy fatigability was present. On examination, she had cyanosis in oral cavity and tongue. There is no history of exposure to any chemicals, antimalarial, fava beans, drug allergy. Considering all the positive finding including saturation gap, a decision was taken to evaluate for methemoglobinemia.
A complete workup including a complete blood count, reticulocyte count, peripheral blood smear, liver function test, renal function tests was done. Cardiology and pulmonology evaluation to rule out secondary causes of cyanosis was also done. Special tests to investigate for methemoglobinemia were also advised done. Her blood investigation is as shown in Table 1.
Genetic analysis revealed a novel mutation (R192C) in CYBR3 gene which is associated with an autosomal recessive congenital methemoglobinemia type 1. NADH-cytochrome b5 reductase (cytb5r) enzyme activities were measured by standard methods, and molecular analysis was performed by polymerase chain reaction followed by DNA sequencing. The interpretation of mutation effect and the molecular modeling were performed by using specific software and PyMOL molecular graphics program. Spectroscopic analysis of the hemolysate showed normal peaks suggesting the absence of Hb-M. Molecular characterization showed a novel homozygous mutation p. Arg192Cys in CYB5R3 gene is an evolutionarily conserved position located in exon 7. This mutation has been elucidated as a possibility of high prevalence of heterozygous in Indian population causing type I restrictive cardiomyopathy. The patient was started on Vitamin C and niacin. Samples were sent for G6PD levels before initiating methylene blue for surgery. Unfortunately, her G6PD levels came back as deficient: 5.9 units/g of Hb (6.97-20.5). She was advised to continue Vitamin C and niacin and to review after 1 month. It was also decided to do a G6PD genetic workup too for the patient.
Her G6PD genetic study was suggestive of G6PD Kerala Kalyan pathogenic heterozygous variant. In India, around 13 variants have been characterized biochemically and as per the mutation studies, the most common variants are G6PD Mediterranean (563 C-->T; 60.4%) followed by G6PD Kerala Kalyan (949 G-->A; 24.5%) and G6PD Orissa (131 C-->G; 13.3%). G6PD Chatham (1003 G-->A) with undetected red cell enzyme activity and G6PD Insuli (989 G-->A) with normal G6PD activity were very rare in the Indian population.
G6PD Kalyan, a mildly deficient variant first described in the Koli, a tribal group inhabiting the Kalyan district of Bombay. G6PD Kerala reported in Indians living in the Pacific North West of America, originating from Kerala state. Both were independently identified and later clubbed together to become Kerala Kalyan pathogenic heterozygous variant G6PD. A single base change was found, namely a G:A transition at nucleotide position 949 in exon 9, resulting in the substitution of lysine for glutamic acid at amino acid position 317. Being a mild variant, she was taken up for surgery with adequate precautions. She reviewed after 1 month with a preoperative saturation of 90% in room air. After detailed discussion with anesthesia department, a patient-specific protocol was formulated to ensure safe surgery. Our plan was to avoid methylene blue and dehydration along with monitoring for acidosis, hypoxia, sensorium, and renal function. Plan for hyperbaric oxygen therapy and exchange transfusion if the need arises was also discussed. Propofol and atracurium were used for induction and muscle relaxation, respectively. Maintenance of anesthesia was achieved using oxygen, air, and sevoflurane. Throughout the surgery, her saturation was maintained at 93%. The surgery and postoperative period were uneventful. She was discharged on postoperative day 4. It was also decided to the send the blood samples of family members for Methemoglobinemia and G6PD genetic screening as it is a rare phenomenon.