Tyrosinemia Type 2: A Patient Guide

Tyrosinemia Type 2, also known as Richner-Hanhart syndrome, is an exceptionally rare genetic condition that fundamentally changes how your child’s body processes protein. In a healthy body, an enzyme called tyrosine aminotransferase acts as a specialized tool to break down an amino acid called tyrosine, which is found in most protein-rich foods ^[1]. For children with this condition, that tool is missing or broken due to changes in the TAT gene, causing tyrosine to build up to high levels in the blood and tissues ^[2]. Because the body cannot clear this buildup on its own, the excess tyrosine eventually forms crystals that irritate and damage the eyes and skin, and can increase the risk of neurological or developmental delays ^[3].

The condition is defined by a “triad” of symptoms that can appear at different times throughout early childhood. The first sign is often intense eye pain and light sensitivity caused by tyrosine crystals on the cornea, which are frequently and incorrectly treated as viral infections like herpes simplex ^[4]. Over time, painful, thickened patches of skin—known as palmoplantar hyperkeratosis—may develop on the palms of the hands and the soles of the feet, making daily activities and walking difficult ^[5]. Perhaps most critically, if tyrosine levels remain high and untreated, the central nervous system can be affected, leading to intellectual disabilities or permanent developmental delays ^[6]. It is important to know that neurological involvement is a variably reported complication, not an inevitability, and early treatment reduces this risk.

Managing Tyrosinemia Type 2 requires a precise, lifelong approach to nutrition that serves as the primary medical treatment. By strictly limiting natural protein according to a metabolic dietitian’s prescription and using a specialized medical formula that provides essential nutrients without tyrosine, parents can effectively lower blood levels and stop the cycle of crystal formation ^[7]. It is vital to note that while some medications, like nitisinone, are lifesaving for other forms of tyrosinemia, they are not standard treatment for Type 2 and can actually make symptoms worse by further raising tyrosine ^[8]. The focus remains entirely on dietary control, which offers a powerful way to support your child’s physical comfort and cognitive future.

While the diagnosis of such a rare condition is life-changing, the path forward is one of active management with your care team. When the diet is maintained and tyrosine levels are kept within a safe range, the painful eye and skin symptoms often improve substantially or resolve completely, sometimes within just a few weeks ^[2]. By working closely with a metabolic care team, families can provide their children with the stability they need to meet their milestones. The diet is demanding, and occasionally dealing with fluctuating levels or needing help does not represent a parental failure ^[7].