A 12-year-old male child presented with progressive lower limb weakness, regression of motor milestones, and 3 episodes of generalized tonic-clonic seizures in the past year. Blood workup was normal except for elevated lactic acid levels. There is a significant family history of similar complaints in the family and the family pedigree is attached. What are the most likely diagnosis and the pattern of inheritance:
LEIGH’S disease; mitochondrial inheritance
Adrenoleukodystrophy; X-linked recessive inheritance
MELAS; mitochondrial inheritance
Duchene muscular dystrophy; X-linked recessive inheritance
Ans.C.MELAS; mitochondrial inheritance
The pedigree has some distinct features like both males and females being affected but only females could transmit it to the successive generations. This pattern is referred to as maternal transmission which is seen in mitochondrial diseases. As mitochondria are only present in the midpiece of spermatozoa which is not involved in zygote formation (only the head of spermatozoa is fused with the ovum), males do not transmit the deleterious mitochondrial genes to the offspring.