Baby boy blue … and mommy too! A rare case of methaemoglobinaemia presenting simultaneously in a mother-neonate pair

Methaemoglobinaemia occurs when there is >1% methaemoglobin in erythrocytes. In an infant, they can present either congenitally or in an acquired form. We present a rare case of methaemoglobinaemia presenting simultaneously in a mother and infant pair. The mother and infant were discharged well on Day-4 post-delivery with both mother and baby recording oxygen saturation levels of 100%. On Day-7, during a routine clinic visit, they were incidentally found to be centrally cyanosed. There were no other abnormalities. On investigation, the methaemoglobin levels were elevated in the infant (23.9%) and mother (14.3%). Treatment with ascorbic acid normalised mother's methaemoglobin levels; but baby's levels remained high until the administration of oral methylene blue. Both baby and mother remained well and pink at last follow-up at 2 years 8 months of age. This case illustrates difficulties in ascertaining the cause of methaemoglobinaemia. Postdelivery, the mother-neonate pair were pink, and their haemoglobin electrophoresis were normal, hence it was unlikely to be congenital methaemoglobinaemia. The team could not identify any triggering factors for acquired methaemoglobinaemia. There was also the uncertainty of the necessity to treat the baby. This is because treatment is not without harmful effects and despite the high methaemoglobin levels, the infant was otherwise well. Only a single published paper recommended that high methaemoglobin levels must be treated, and the recommendation was not supported by evidence. Lessons learnt from our case are that neonates with methaemoglobinaemia can be safely treated with oral methylene blue, but more research is needed on the benefitrisk profile of treatment.