Background: Tyrosinemia type 1 (TYRSN1) is an autosomal recessive metabolic disease that occurs due to a defect in the enzyme fumarylacetoacetate hydroxylase. In the case of a defect in this enzyme, toxic metabolites resulting from the breakdown of tyrosine accumulate in vital organs, leading to various symptoms and problems in these patients.

Patient presentation:

A 3-year-old boy was admitted to the hospital with confusion, constipation, vomiting, abdominal pain, fever, oliguria, and anorexia. On examination, hypertension, genu varum, abnormal gait, and urinary retention were observed. Laboratory tests revealed hypoglycemia, glucosuria, metabolic acidosis, anemia, hypokalemia, and hypocalcemia. Ultrasound and CT scans revealed large kidneys and a heterogeneous liver, with multiple nodules. Additional tests revealed elevated alkaline phosphatase, a high alpha-fetoprotein level, hypophosphatemia, and increased urinary excretion of phosphorus and potassium. Hand radiography also revealed rickets. Finally, due to suspicion of hereditary diseases of amino acid metabolism, blood and urine chromatography revealed a marked accumulation of tyrosine. The diagnosis of chronic TYRSN1 was confirmed by measuring high urinary excretion of succinylacetone. The patient was treated with Nitisinone and a restricted diet of tyrosine and phenylalanine, and within 1 week, he showed a dramatic response to treatment.

Conclusion:

Our patient was a case of chronic TYRSN1 who, owing to a lack of timely diagnosis, had symptoms of neurological crises similar to acute porphyria, as well as symptoms of Fanconi syndrome-type renal tubular disorder and rickets. Due to the rarity of this disease and its diverse clinical manifestations, its diagnosis is challenging in countries such as Iran, where screening for this disease is not performed, and most patients are diagnosed when they have severe complications.