MedGen

Increased height of the central portion of the eyebrow, forming a crescent, semicircular, or inverted U shape. [from HPO]

U wave inversion that is induced by exercise stress testing. [from HPO]

Direction of the U wave opposite to the T wave (i.e., below baseline) in leads with upright T waves. [from HPO]

Increased amplitude of the U wave, defined as an amplitude greater than 1-2mm or 25 percent of the height of the T wave. [from HPO]

Fanconi anemia (FA) is characterized by physical abnormalities, bone marrow failure, and increased risk for malignancy. Physical abnormalities, present in approximately 75% of affected individuals, include one or more of the following: short stature, abnormal skin pigmentation, skeletal malformations of the upper and/or lower limbs, microcephaly, and ophthalmic and genitourinary tract anomalies. Progressive bone marrow failure with pancytopenia typically presents in the first decade, often initially with thrombocytopenia or leukopenia. The incidence of acute myeloid leukemia is 13% by age 50 years. Solid tumors – particularly of the head and neck, skin, and genitourinary tract – are more common in individuals with FA. [from GeneReviews]

An anomaly of the U wave of the electrocardiogram (EKG). The U wave is a small (0.5 mm) deflection immediately following the T wave, usually in the same direction as the T wave. It is best seen in leads V2 and V3. [from HPO]

MN antigens reside on GYPA, one of the most abundant red-cell glycoproteins. The M and N antigens are 2 autosomal codominant antigens encoded by the first 5 amino acids of GYPA and include 3 O-linked glycans as part of the epitope. M and N differ at amino acids 1 and 5, where M is ser-ser-thr-thr-gly, and N is leu-ser-thr-thr-glu. M is the ancestral GYPA allele and is common in all human populations and Old World apes. GYPA, glycophorin B (GYPB; 617923), and glycophorin E (GYPE; 138590) are closely linked on chromosome 4q31. The N terminus of GYPB is essentially identical to that of GYPA except that it always expresses the N antigen, denoted 'N' or N-prime. Antigens of the Ss blood group (111740) reside on GYPB, and recombination and gene conversion between GYPA, GYPB, and GYPE lead to hybrid glycophorin molecules and generation of low-incidence antigens. Thus, the MN and Ss blood groups are together referred to as the MNSs or MNS blood group system. The U antigen refers to a short extracellular sequence in GYPB located near the membrane. Recombination results in 3 glycophorin-null phenotypes: En(a-) cells lack GYPA due to recombination between GYPA and GYPB; GYPB-negative (S-s-U-) cells lack GYPB due to recombination in GYPB; and M(k) cells (M-N-S-s-U-) lack both GYPA and GYPB due to recombination between GYPA and GYPE. Individuals with glycophorin-null phenotypes have decreased sialic acid content and increased resistance to malarial infection (see 611162). GYPA and GYPB are not essential for red-cell development or survival, and GYPA- and GYPB-null phenotypes are not associated with anemia or altered red-cell function (review by Cooling, 2015). [from OMIM]

LQT16 Long QT syndrome-16 (LQT16) is characterized by a markedly prolonged corrected QT (QTc) interval and 2:1 atrioventricular (AV) block, with onset in the perinatal period. Patients experience bradycardia or ventricular tachyarrhythmias that may result in syncope, cardiac arrest, and/or sudden death (Reed et al., 2015; Wren et al., 2019). Patients with LQT14 (616247), LQT15 (616249), or LQT16, resulting from mutation in calmodulin genes CALM1 (114180), CALM2 (114182), or CALM3, respectively, typically have a more severe phenotype, with earlier onset, profound QT prolongation, and a high predilection for cardiac arrest and sudden death, than patients with mutations in other genes (Boczek et al., 2016). CPVT6 Catecholaminergic polymorphic ventricular tachycardia-6 (CPVT6) is characterized by childhood-onset syncopal episodes with exercise or stress. Electrocardiogram (ECG) shows a normal QT interval with a prominent U wave, and stress testing reveals premature ventricular contractions (PVCs) that may occur as bigeminy or couplets, and nonsustained ventricular tachycardia (Gomez-Hurtado et al., 2016). [from OMIM]

Ss blood group antigens reside on the red-cell glycoprotein GYPB. The S and s antigens result from a polymorphism at amino acid 29 of GYPB, where S has met29 and s has thr29. The U antigen refers to a short extracellular sequence in GYPB located near the membrane. GYPB, glycophorin A (GYPA; 617922), and glycophorin E (GYPE; 138590) are closely linked on chromosome 4q31. Antigens of the MN blood group (111300) reside on GYPA. The M and N antigens differ at amino acids 1 and 5 of GYPA, where M is ser-ser-thr-thr-gly, and N is leu-ser-thr-thr-glu. The N terminus of GYPB is essentially identical to that of GYPA except that it always expresses the N antigen, denoted 'N' or N-prime. Recombination and gene conversion between GYPA, GYPB, and GYPE lead to hybrid glycophorin molecules and generation of low-incidence antigens. Thus, the MN and Ss blood groups are together referred to as the MNSs blood group system (see 111300). Recombination results in 3 glycophorin-null phenotypes: En(a-) cells lack GYPA due to recombination between GYPA and GYPB; GYPB-negative (S-s-U-) cells lack GYPB due to recombination in GYPB; and M(k) cells (M-N-S-s-U-) lack both GYPA and GYPB due to recombination between GYPA and GYPE. Individuals with glycophorin-null phenotypes have decreased sialic acid content and increased resistance to malarial infection (see 611162). GYPA and GYPB are not essential for red-cell development or survival, and GYPA- and GYPB-null phenotypes are not associated with anemia or altered red-cell function (review by Cooling, 2015). [from OMIM]

Uncombable hair syndrome is characterized by silvery, blond, or straw-colored scalp hair that is dry, frizzy, and wiry, has a characteristic sheen, stands away from the scalp in multiple directions, and is impossible to comb. This hair shaft disorder occurs in children and improves with age. The hair growth rate can range from slow to normal (summary by U. Basmanav et al., 2016). Genetic Heterogeneity of Uncombable Hair Syndrome See UHS2 (617251), caused by mutation in the TGM3 gene (600238) on chromosome 20p12, and UHS3 (617252), caused by mutation in the TCHH gene (190370) on chromosome 1q21. [from OMIM]

Uncombable hair syndrome (UHS) is characterized by silvery, blond, or straw-colored scalp hair that is dry, frizzy, and wiry, has a characteristic sheen, stands away from the scalp in multiple directions, and is impossible to comb. This hair shaft disorder occurs in children and improves with age. The hair growth rate can range from slow to normal (summary by U. Basmanav et al., 2016). For a general phenotypic description and a discussion of genetic heterogeneity of UHS, see UHS1 (191480). [from OMIM]

Uncombable hair syndrome (UHS) is characterized by silvery, blond, or straw-colored scalp hair that is dry, frizzy, and wiry, has a characteristic sheen, stands away from the scalp in multiple directions, and is impossible to comb. This hair shaft disorder occurs in children and improves with age. The hair growth rate can range from slow to normal (summary by U. Basmanav et al., 2016). For a general phenotypic description and a discussion of genetic heterogeneity of UHS, see UHS1 (191480). [from OMIM]

Myelodysplastic syndrome (MDS) is a heterogeneous group of clonal hematologic stem cell disorders characterized by ineffective hematopoiesis resulting in low blood counts, most commonly anemia, and a risk of progression to acute myeloid leukemia (AML; 601626). Blood smears and bone marrow biopsies show dysplastic changes in myeloid cells, with abnormal proliferation and differentiation of 1 or more lineages (erythroid, myeloid, megakaryocytic). MDS can be subdivided into several categories based on morphologic characteristics, such as low-grade refractory anemia (RA) or high-grade refractory anemia with excess blasts (RAEB). Bone marrow biopsies of some patients show ringed sideroblasts (RARS), which reflects abnormal iron staining in mitochondria surrounding the nucleus of erythrocyte progenitors (summary by Delhommeau et al., 2009 and Papaemmanuil et al., 2011). [from OMIM]

A group of myeloid neoplasms that includes the following: chronic myeloid leukemia, BCR-ABL1 positive; polycythemia vera; essential thrombocythemia; primary myelofibrosis; chronic neutrophilic leukemia; chronic eosinophilic leukemia, not otherwise specified; and myeloproliferative neoplasm, unclassifiable. [from NCI]

Gentle upward curve of the upper lip vermilion such that the center is placed well superior to the commissures. [from HPO]

Chronic myeloproliferative disease, unclassifiable is a hematological neoplasm characterized by clonal proliferation of myeloid precursors in the bone marrow, blood and other tissues (spleen, liver), with clinical, morphological and molecular features of myeloproliferative neoplasms (MPN), failing to meet criteria of a specific MPN. The presentation is nonspecific and variable and often includes leukocytosis, thrombocytosis and anemia. Splenomegaly, hepatomegaly as well as fatigue, malaise or weight loss may appear in advanced stages. [from ORDO]

Autosomal recessive spinocerebellar ataxia-16 (SCAR16) is a progressive neurologic disorder characterized by truncal and limb ataxia, resulting in gait instability, associated with cerebellar atrophy on brain imaging. Most patients have onset in the teenage years, although earlier and later onset have been reported. Additional features may include dysarthria, nystagmus, hyperreflexia of the lower limbs, and mild peripheral sensory neuropathy. Some patients have gonadal dysfunction or hypogonadism and/or cognitive deficits. The phenotype represents a spectrum or continuum of neurodegenerative features that may overlap with those of SCA48 (summary by Shi et al., 2013 and Ravel et al., 2021). [from OMIM]