Sickle Cell Disease (SCD) is an autosomal recessive disorder characterized by an abnormal molecular structure of hemoglobin. The core etiology is a point mutation in the HBB gene encoding the hemoglobin beta chain. This causes hemoglobin to polymerize abnormally under hypoxic conditions, deforming red blood cells from their normal biconcave disc shape into rigid sickle shapes. These abnormally shaped cells tend to obstruct microvessels, leading to tissue ischemia, pain, multi-organ damage, and chronic anemia due to their premature destruction, which can be life-threatening in severe cases. The disease affects millions globally, with high incidence in Africa, the Mediterranean region, and elsewhere. Sickle cell anemia (HbSS type) is the most common form, accounting for approximately 70% of cases in people of African descent. Patients often present with recurrent pain crises, increased risk of infections, and dysfunction of various organs.

What is Spinocerebellar Ataxia? Spinocerebellar Ataxia (SCA) is a group of neurodegenerative diseases caused by mutations in different genes. The underlying causes are diverse, typically involving mutations in various genes, with many subtypes linked to dynamic mutations like CAG trinucleotide repeat expansions. Core clinical symptoms include progressive gait instability, limb incoordination, dysarthria, and abnormal eye movements. Different subtypes may also present with other neurological manifestations such as peripheral neuropathy, cognitive decline, and extrapyramidal symptoms. The global incidence is approximately 1-5 per 100,000. Among Chinese SCA patients, SCA3 is the most prevalent, accounting for 51.1% to 72.5%.

Progressive Familial Intrahepatic Cholestasis (PFIC) is a group of inherited disorders caused by various autosomal recessive mutations. It results from the inability of hepatocytes to properly form and secrete bile due to specific gene mutations, which can ultimately progress to liver failure. PFIC has three classic types: PFIC-1, PFIC-2, and PFIC-3. The incidence of PFIC-1 and PFIC-2 is approximately 1/100,000 to 1/50,000.

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.