Pentasomy 49,XXXXY occurs in 1/85,000 newborn males. The origin of this particular form of aneuploidy is believed to be a result of consecutive nondisjunction events during maternal meiosis. Typical presentation consists of hypotonia, developmental delay, various dysmorphic features, and severe hypogenitalism. A 13-year-old with pentasomy 49,XXXXY and a Chiari type 1 malformation with an associated cervical syrinx is presented.

1.
Kleczkowska A, Fryns JP, Van den Berghe H: X-chromosome polysomy in the male. The Leuven experience 1966–1987. Hum Genet 1988;80:16–22.
2.
Huang TH, Greenberg F, Ledbetter DH: Determination of the origin of nondisjunction in a 49,XXXXY male using hyperlvariable dinucleotide repeat sequences. Hum Genet 1991;86:619–620.
3.
Clatterbuck RE, Sipos EP: The efficient calculation of neurosurgically relevant volumes from computed tomographic scans using Cavalieri’s direct estimator. Neurosurgery 1997;40:339–343.
4.
Tubbs RS, Webb D, Abdullatif H, Conklin M, Doyle S, Oakes WJ: Posterior cranial fossa volume in patients with rickets: insights into the increased occurrence of Chiari 1 malformation in metabolic bone disease. Neurosurgery 2004;55:380–384.
5.
Sarto GE, Otto PG, Kuhn EM, Therman E: What causes the abnormal phenotype in a 49,XXXXY male? Hum Genet 1987;76:1–4.
6.
Linden MG, Bender BG, Robinson A: Sex chromosome tetrasomy and pentasomy. Pediatrics 1995;96:672–682.
7.
Hecht F: Observations on the natural history of 49,XXXXY individuals. Am J Med Genet 1982;13:335–336.
8.
Sheridan MK, Radlinski SS, Kennedy MD: Developmental outcome in 49,XXXXY Klinefelter syndrome. Dev Med Child Neurol 1990;32:532–539.
9.
Boraz R: XXXXY syndrome: report of a case. J Clin Pediatr Dent 1995;19:143–146.
10.
Cammarata M, Di Simone P, Graziano L, Giuffre M, Corsello G, Garofalo G: Rare sex chromosome aneuploidies in humans: report of six patients with 48,XXYY, 49,XXXXY, and 48,XXXX karyotypes. Am J Med Genet 1999;85:86–87.
11.
Christodorescu D, Constantinescu E, Ciovirnache M, Costiner E: 49,XXXXY syndrome with profound mental deficiency. Neurol Psychiatr (Bucur) 1978;16:79–84.
12.
Peet J, Weaver DD, Vance GH: 49,XXXXY: a distinct phenotype. Three new cases and review. J Med Genet 1998;35:420–424.
13.
Terheggen HG, Pfeiffer RA, Haug H, Schunke W: Das XXXXY-Syndrom. Bericht über 7 neue Fälle und Literaturübersicht. Z Kinderheilkd 1973;115:209–233.
14.
Singh TH, Rajkowa S: 49,XXXXY chromosome anomaly: an unusual variant of Klinefelter’s syndrome. Br J Psychiatry 1986;148:209–210.
15.
Tumba A, Laredo JD, Corvol MT, Welkenhausen R, Cleuren M, van Ongevalle AM, Vercruysse JP, van den Berghe H: Evolution of bone anomalies in 49,XXXXY syndrome. Can Assoc Radiol J 1993;44:107–111.
16.
Haeusler G, Frisch H, Guchev Z, Hadziselimovic F, Neuhold A, Vormittag W: Hypoplasia of the corpus callosum and growth hormone deficiency in the XXXXY syndrome. Am J Med Genet 1992;44:230–232.
17.
Atkinson JL, Kokmen E, Miller GM: Evidence of posterior fossa hypoplasia in the familial variant of adult Chiari 1 malformation: case report. Neurosurgery 1998;42:401–404.
18.
Nishikawa M, Sakamoto H, Hakuba A, Nakanishi N, Inoue Y: Pathogenesis of Chiari malformation: a morphometric study of the posterior cranial fossa. J Neurosurg 1997;86:40–47.
19.
Nyland H, Krogness KG: Size of posterior fossa in Chiari type 1 malformation in adults. Acta Neurochir (Wien) 1978;40:233–242.
20.
Stanzani P, Bruno L, Pollari Maglietta E, Sorrenti G, Gobbi G: A case of heredo-ataxia in a subject with karyotype 49,XXXXY. Brain Dev 1986;8:570–571.
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