An Unusual Case of Feeding Intolerance in a 7 Month Old Female

Abstract

Purpose: Background: Aromatic L-amino acid decarboxylase deficiency (AADC) is an inborn error in neurotransmitter metabolism caused by mutations in the dopa decarboxylase (aromatic L-amino acid decarboxylase) gene, which leads to combined serotonin and catecholamine deficiency. Symptoms include severe developmental delay, hypotonia, muscle stiffness, athetosis, lethargy, feeding intolerance, sleep disturbances, oculogyric crises, extreme irritability, pain, muscle spasms, and uncontrolled movements. Patient: A 7 month old Caucasian female with a history of hypotonia and developmental motor delay presented with excessive irritability and feeding intolerance. Clinical Course: She was well until 3-4 months of age, when she became inconsolable, had non-bilious, non-bloody emesis, and irritability with feeds. Symptoms worsened over the last 3 months. She had decreased activity, poor eye tracking, and hypotonia. Initial workup showed normal gastric emptying scan, MBS revealing frank aspiration, and pH probe showed copious reflux, so a Nissen fundoplication with gastric feeding tube was placed. Lorazepam and phenobarbital did not have a perceived effect. Additional workup included an EEG, head CT scan, head MRI, karyotype, serum lactate level, serum ammonia level, and plasma amino acids which were all within normal limits except for a low cysteine level. Urine organic acids showed minimal dicarboxylic acids and acetylcarnitine profile showed a mildly elevated C4OH due to diet or a ketotic state. Magnetic resonance spectroscopy (MRS) was notable for nonspecific lactate spikes. Because of suspicion of a possible mitochondrial or neurotransmitter disorder, a lumbar puncture was performed. Neurotransmitter analysis and plasma enzymology confirmed the diagnosis of AADC. Pyridoxal-5-phosphate (coenzyme B6) and ropinirole (a dopamine agonist) were added, in addition to hyoscyamine, pantoprazole, and sucralfate. Two months after diagnosis, she has been tolerating feeds with less irritability. Conclusion: Children with feeding disorder, developmental delay and hypotonia should have a work-up for inborn errors of metabolism. Initial laboratory workup should include CBC, electrolytes, LFTs, urine organic acids, blood amino acids and acylcarnitine profile, total and free carnitine levels, as well as an MRI and MRS.