Congenital Methaemoglobinaemia.

Spectroscopy and  spectrograph will confirm  the  Dianosis.

Oral  Methylene Blye  is  the  treatment  of  Choice.

PLEASE CHECK IT

pmj.bmj.com › Volume 75, Issue 889

Yes,This is case of Congenital Methaemoglobinaemia.

Pulse oximetry may be helpful in detecting methaemoglobinaemia. Pulse oximeter measures the light absorbance changes by arterial pulsations at only two wavelengths, one in the red (660 nm) and the other in the near infrared (940 nm) range. Methaemoglobin has a high absorbance at both wavelengths, tending to drive the ratio of absorbance toward 1, which corresponds to an oxygen saturation of nearly 85%. Hence, with a high level of methaemoglobin in the blood, pulse oximeter readings will tend to be around 85%. In contrast, the saturation as reported on an arterial blood gas is a calculated value based on the partial pressure of dissolved oxygen and assumes no abnormal haemoglobin is present. Therefore, the reported oxygen saturation from the laboratory is generally higher than that measured with a pulse oximeter. This difference is called the saturation gap and is typically more than 5% in patients with methaemoglobinaemia. Qualitative confirmation of methaemoglobinaemia is done by blood spectrophotometry. Once confirmed, electrophoresis of haemoglobin and estimation of methaemoglobin reductase are required to diagnose the cause of methaemoglobinaemia.

Patients with methaemoglobinaemia who have cyanosis and systemic manifestations need to be treated. In severe cases, intravenous methylene blue is required. Methylene blue is reduced to leucomethylene blue by NADPH. In turn, leucomethylene blue reduces methaemoglobin to haemoglobin. The recommended dose is 1–2 mg/kg of 1% solution administered over 5 minutes and the same dose may be repeated in one hour if symptoms of hypoxia persist. Cumulative doses of methylene blue exceeding 7 mg/kg may cause dyspnoea, chest pain, tremor, cyanosis and haemolysis. As the efficacy of methylene blue depends on adequate amounts of NADPH, care should be taken to exclude glucose-6-phosphate dehydrogenase (G6PD) deficiency. Methylene blue can produce methaemoglobinaemia in patients who are G6PD deficient. Due to its slow action, ascorbic acid is not recommended as the only method of treatment in toxic methaemoglobinemia. Exchange transfusion may be required in severe cases not responding to methylene blue, when G6PD deficiency precludes use of methylene blue, or in case of aniline poisoning. Since patients with congenital NADH-cytochrome b5 reductase deficiency are usually asymptomatic except for cyanosis, no treatment is indicated; however, for cosmetic purposes, ascorbic acid may be administered. It has a direct reducing action on methaemoglobin. Reduction of cyanosis is appreciated clinically about 9 to 10 days after therapy with ascorbic acid.8 No treatment is available for methaemoglobinaemia due to M haemoglobins

Great contribution Dr Khaleque! Do you see this condition often ?

As  such  Congenital Methaemoglobinaemia  is  a  very  rare  entity.  However Methaemoglobinaemia  occurs  secondary  to 1) Copper  Sulphate  Poisoning 2 ) People  drinking  water that  contains  high  Nitrites (  In  India in Andra  Predesh State - the well water  contains  more nitrites ) and  excess consumption  of  this  water  result  in  methaemoglobinaemia 3) people  who  consume  anti termite  poisoning.  In  toxicology  unit  of  Govt.  Stanley  Hospital on  an  average  we  treat  3-4 cases every  month  of  secondary  Methaemoglobinaemia  with  intravenous Methylene  blue  and  they  readily  respond  to  treatment.