International Rare Disease Day The last day of February each year is International Rare Disease Day. This year's theme is "More than you can imagine." Rare diseases, often referred to as "orphan diseases," are conditions with extremely low incidence rates but severe, often life-threatening symptoms. Over 7,000 rare diseases are known globally, affecting more than 300 million people, with over 20 million patients in China. These patients face challenges in diagnosis, access to medication, healthcare coverage, and social integration.

Ornithine Transcarbamylase Deficiency (OTCD), also known as hyperammonemia type II, is an X-linked inherited metabolic disorder caused by mutations in the ornithine transcarbamylase (OTC) gene, leading to reduced or absent activity of the OTC enzyme, thereby interrupting the urea cycle. It is the most common type of urea cycle disorder (UCD), accounting for approximately 50%-67% of all cases, with an estimated incidence of 1/80,000 to 1/56,500.

Hereditary Tyrosinemia is a group of inherited metabolic disorders caused by deficiencies of specific enzymes in the tyrosine metabolic pathway. Based on the deficient enzyme, it is clinically classified into three main subtypes: Type I (HT1), Type II (TAT deficiency), and Type III (HPD deficiency).

Retinoblastoma (RB) is the most common intraocular tumor in children, triggered by biallelic mutations in the RB1gene or amplification of the MYCNoncogene. RB can be unilateral (60%-70%) or bilateral (30%-40%). Bilateral tumors are typically hereditary and present at an earlier age. Retinoblastoma accounts for 2% to 4% of childhood malignancies and is a common primary tumor of the eye. The global incidence in newborns is approximately 1 in 16,000.

Neuroblastoma (NB) is the most common extracranial solid tumor in children, accounting for approximately 8%-10% of pediatric malignancies. Due to its extremely heterogeneous clinical manifestations, it is known as the "king of childhood tumors."