Infantile Dysmorphic Sialidosis (Sialidosis Type II, Infantile Form) Overview Sialidosis is a rare autosomal recessive lysosomal storage disease caused by deficiency of the lysosomal enzyme neuraminidase‑1 (sialidase) due to pathogenic variants in the NEU1 gene on chromosome 6p21.3. Defective NEU1 activity leads to progressive lysosomal accumulation and urinary excretion of sialylated glycoproteins and oligosaccharides, particularly …
Immigration Delay Disease (Adermatoglyphia) Overview “Immigration delay disease” is an informal name coined for adermatoglyphia, a rare inherited absence of epidermal ridges that results in missing fingerprints. The term arose because the condition can create practical problems during travel and border control when fingerprint-based identification is required. Trusted medical sources describe it as isolated congenital …
Iminoglycinuria Iminoglycinuria is a rare, usually benign, inherited defect of renal tubular amino‑acid transport characterized by excessive urinary excretion of glycine and the imino acids proline and hydroxyproline, due to impaired reabsorption in the proximal tubule. It is classically inherited as an autosomal recessive trait, often asymptomatic, and may also appear transiently as a normal …
Imerslund Grasbeck syndrome Imerslund–Gräsbeck syndrome (IGS) is a rare autosomal recessive cause of childhood vitamin B12 deficiency characterized by selective intestinal malabsorption of cobalamin, typically presenting with megaloblastic anemia and mild, non‑progressive low–molecular‑weight proteinuria, due to mutations in the CUBN or AMN genes encoding the ileal “cubam” receptor. With lifelong parenteral vitamin B12 replacement, hematologic …
Illum syndrome – Introduction Illum syndrome is an extremely rare, usually lethal, autosomal recessive form of arthrogryposis multiplex congenita characterized by multiple joint contractures, a distinctive “whistling” facial appearance with microstomia, severe neurologic dysfunction, and early death in infancy. It is now generally classified as arthrogryposis multiplex congenita–whistling face syndrome (AMC‑WFS) and considered part of …
IgG4 Related Mesenteritis (IgG4 Related Sclerosing Mesenteritis) Overview and nomenclature IgG4-related mesenteritis is a rare fibroinflammatory disorder of the small-bowel mesentery that belongs to the spectrum of IgG4-related disease (IgG4-RD) and presents histologically as sclerosing mesenteritis with IgG4-rich inflammation. Orphanet defines it as a subtype of sclerosing mesenteritis, a disease characterized by chronic inflammation and …
Idiopathic CD4 Lymphocytopenia (ICL) Overview and definition Idiopathic CD4 lymphocytopenia (ICL) is a rare acquired primary immunodeficiency defined by a persistent, unexplained decrease in circulating CD4 T lymphocytes in individuals without HIV infection or any other identifiable cause of CD4 lymphopenia. The US Centers for Disease Control and Prevention (CDC) first formalized the definition in …