A 9 month child was taken to pediatric OPD by his mother. Mother complained of the child having lethargy, convulsions, fine tremors, failure to thrive & areas of patchy hair loss on scalp. On investigation, serum ammonia and glutamine levels were increased. Microscopic examination reveals following findings in hair. Which enzyme deficiency is responsible for above symptoms?

Microscopic analysis of the hair shaft showing breaks located at nodes in the hair (Trichorrhexis nodosa) and longitudinal breaks Based on above complains & investigations findings the child is suffering from Arginosuccinic aciduria. It is due to arginosuccinate lyase deficiency. It is characterised by symptoms of other urea cycle disorder along with patchy hair loss on scalp known as Trichorrhexis nodosa.