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What is Absent parathyroid, thymic aplasia with immunodeficiency and heart defects are features of and explain in detail?
Ans. c (Di george syndrome) (Ref. Harrison's medicine 17th ed., Ch. 310)22q11 deletion syndromes:# DiGeorge syndrome --thymic, parathyroid, and cardiac defects. Occurs Due to aberrant development of 3rd and 4th branchial pouches. Cleft palate, Abnormal facies, Thymic aplasia T-cell deficiency, Cardiac defects, Hypocalcemia 2deg to parathyroid aplasia, due to microdeletion at chromosome 22q11.# Velocardiofacial syndrome-palate, facial, and cardiac defects.THE DIGEORGE SYNDROME# classic example of isolated T cell deficiency# results from maldevelopment of thymic epithelial elements derived from the 3rd and 4th pharyngeal pouches.# The gene defect is on chromosomal position 22q11 in most patients with the DiGeorge syndrome.# Defective development of organs dependent on cells of embryonic neural crest origin includes:- Congenital cardiac defects, particularly those involving the great vessels;- Hypocalcemic tetany, due to failure of parathyroid development; and- Absence of a normal thymus.# Facial abnormalities may include abnormal ears, shortened philtrum, micrognathia, and hypertelorism.# Serum immunoglobulin concentrations are frequently normal, but antibody responses, particularly of IgG and IgA isotypes, are usually impaired. T cell levels are |, whereas B cell levels are normal.Pendred syndromeAn autosomal-recessive syndrome consisting of a bilateral congenital sensorineural hearing loss and goiter years later in mid-childhood. T4 levels are usually low to absent, and a perchlorate test is diagnostic. The hearing loss is nonreversible.Also Know:Features of Polyglandular Autoimmune (PGA) syndromesPGA IPGA IIAutosomal recessivePolygenic inheritanceMutations in APECED geneHLA-DR3 and HLA-DR4 associatedChildhood onsetAdult onsetEqual male:female ratioFemale predominanceDisease Associations Mucocutaneous candidiasisAdrenal insufficiencyHypoparathyroidismHypogonadismAdrenal insufficiencyGraves' diseaseHypogonadismType 1 diabetesAlopeciaHypothyroidismDental enamel hypoplasiaMyasthenia gravisMalabsorptionVitiligoChronic active hepatitisAlopeciaVitiligoPernicious anemiaPernicious anemiaCeliac disease