Unveiling the unexpected: refractory rickets as an uncommon presentation of tyrosinemia type I.

backgroundTyrosinemia type I is a rare autosomal recessive inborn error of metabolism caused by deficiency of fumarylacetoacetate hydrolase (FAH), an enzyme essential for the final breakdown of tyrosine. The enzyme defect leads to accumulation of toxic metabolites, primarily affecting the liver, kidneys, and brain. Typically, diagnosed in infancy due to acute or chronic liver dysfunction, refractory rickets is an uncommon presentation. We report a child with tyrosinemia type I presenting with refractory rickets and hepatosplenomegaly but with preserved liver function. CASE PRESENTATION: A three-year-old child presented with bilateral limb deformities unresponsive to multiple courses of vitamin D and calcium. The child also exhibited floppiness, polyuria, and polydipsia. Evaluation revealed hepatomegaly and hypophosphatemic rickets secondary to Fanconi syndrome, later confirmed to be due to tyrosinemia type I. The child was treated with phosphate supplementation, nitisinone, and a tyrosine- and phenylalanine-restricted diet, with favorable follow-up.

conclusionTyrosinemia type I may present beyond infancy with renal-predominant manifestations such as refractory rickets and preserved hepatic function. Early diagnosis and treatment are essential to prevent progression and mortality.