Congenital Adrenal Hyperplasia (CAH) is a group of autosomal recessive genetic disorders caused by defects in key enzymes involved in adrenal corticosteroid synthesis. The core feature is impaired cortisol synthesis, which through negative feedback mechanisms leads to compensatory increased secretion of adrenocorticotropic hormone (ACTH), stimulating adrenal cortical hyperplasia while causing abnormal accumulation of precursor substances such as androgens.

What is Retinitis Pigmentosa? Retinitis Pigmentosa (RP) is a genetically heterogeneous retinal degenerative disorder characterized pathologically by progressive photoreceptor cell death and retinal pigment epithelium (RPE) atrophy. Common clinical manifestations include night blindness, progressive visual field constriction, and gradual loss of central vision. Typical fundoscopic findings reveal bone spicule-like pigment deposits, generalized attenuation of retinal vessels, and waxy pallor of the optic disc, constituting the classic "triad." Research indicates that RP pathogenesis is closely associated with multiple gene mutations and protein metabolism abnormalities. Based on inheritance patterns, RP is classified into three main types: autosomal dominant (adRP, accounting for approximately 15%–25%), autosomal recessive (arRP, approximately 5%–20%), and X-linked (XLRP, approximately 10%–15%).

What is Niemann-Pick Disease? Niemann-Pick Disease (NPD) is an autosomal recessive inherited lysosomal storage disorder, also known as sphingomyelin-cholesterol lipidosis. Based on pathogenesis and clinical manifestations, NPD is primarily classified into two major categories: A/B type and C type.

What is Hemophilia? Hemophilia is an X-linked recessive inherited bleeding disorder caused by pathogenic variants in the F8 gene located at Xq28 or the F9 gene at Xq27 of the X chromosome, leading to impaired synthesis and function of coagulation factor VIII (FVIII) or coagulation factor IX (FIX), respectively. Clinically, it manifests as spontaneous or post-traumatic bleeding due to impaired thrombin generation. The global actual prevalence of hemophilia is approximately 17.1 per 100,000 male residents. Among these, hemophilia A (HA) caused by FVIII deficiency accounts for 80%-85%, while hemophilia B (HB) caused by FIX deficiency accounts for 15%-20%. Based on plasma coagulation factor activity levels (FVIII:C/FIX:C), it can be classified as severe (<1 IU/dL), moderate (1-5 IU/dL), or mild (5-40 IU/dL).

What is Methylmalonic Acidemia? Methylmalonic Acidemia (MMA) is an autosomal recessive inherited organic acid metabolism disorder that typically manifests in the neonatal period or early infancy. The disease has an insidious onset and rapid progression, presenting with multisystem involvement. Characteristic neurological manifestations include intellectual disability, hypotonia, basal ganglia stroke-like lesions, and hyperammonemic encephalopathy. Metabolic disturbances may present as ketosis, hyperglycinemia, and metabolic acidosis. Multiorgan involvement can affect the kidneys (chronic renal failure), vision (optic atrophy), hearing (sensorineural deafness), bones (osteoporosis, short stature), and hematopoietic system (bone marrow failure). Patients often experience concurrent liver and kidney damage. Newborn screening data indicate a birth prevalence of approximately 1/28,000.