RESUMEN
Tetrasomy 20p is a very rare chromosome abnormality, with only two single cases previously reported in the literature, both fetuses with multiple congenital anomalies, osteopenia, and fractures. We report on the first case of mosaic tetrasomy 20p in a 13-year-old male. Amniocentesis karyotype showed mosaicism (73% of cells) for a supernumerary marker chromosome, an isodicentric chromosome 20p. At birth, cord blood karyotype was normal in all cells but uroepithelial cells showed the marker chromosome in 30% of cells analyzed. Chromosomal single nucleotide polymorphism (SNP) microarray using buccal cells confirmed the previous result with mosaicism estimated at 59% of cells. His course has been complicated by profound osteoporosis with recurrent nontraumatic fractures and vertebral compression leading to significant disability. This report describes the phenotype and evaluation of mosaic pure tetrasomy 20p syndrome and compares to nonmosaic tetrasomy 20p and trisomy 20p syndromes, both of which have been previously reported in association with osteopenia and fractures. The pathophysiology of osteoporosis in tetrasomy 20p is unknown. We hypothesize that overexpression of bone morphogenetic protein 2 may be the underlying mechanism of osteoporosis and recurrent fractures.
Asunto(s)
Trastornos de los Cromosomas/genética , Cromosomas Humanos Par 20/genética , Fracturas Espontáneas/genética , Mosaicismo , Osteoporosis/genética , Tetrasomía/genética , Adolescente , Marcadores Genéticos/genética , Humanos , Cariotipo , Masculino , Análisis por Micromatrices , Polimorfismo de Nucleótido Simple/genética , Urotelio/metabolismoRESUMEN
Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by development of autoantibodies to nuclear and cytoplasmic antigens. A small subset of SLE patients who had the typical clinical features of SLE was reported to show persistently negative antinuclear antibody tests. Our report describes a 5-year-old male who presented with histopathological findings suggestive of lupus nephritis with no clinical signs or symptoms of SLE and negative autoantibodies. He was treated with corticosteroids, mycophenolate mofetil, and monthly intravenous cyclophosphamide. During the 2-year follow-up period, the proteinuria resolved and kidney function improved with continued negative autoantibody workup. This case presents a category of renal-limited "lupus-like" glomerulonephritis which can be challenging to treat and carries a poor prognosis.