title: Identification of IgG-κ type macroprolactin found in the serum of an 8-year-old girl.
abstract: BACKGROUND
  We report a case of macroprolactin (macroPRL) in an 8-year-old girl complaining of an enlarged and painful breast who showed elevated PRL levels by enzyme immunoassay.
  
  
  METHODS
  Size-exclusion high-performance liquid chromatography (HPLC) was carried out on a Superose 12 column to estimate the PRL molecular profile. To identify the type of immunoglobulin bound to PRL, immunoprecipitation reactions were performed using three types of anti-heavy chain antibody and two types of anti-light chain.
  
  
  RESULTS
  PRL in the patient's serum was eluted at a size slightly larger than the IgG peak by size-exclusion HPLC on a Superose 12 column. In the immunoprecipitation reaction, the PRL concentration of the supernatant mixed with anti-gamma heavy chain and anti-κ light chain was dramatically decreased compared to other types of antiserum. These results indicated that macromolecular PRL was composed of PRL and IgG-κ.
  
  
  CONCLUSIONS
  A rare case of PRL-IgG-κ-type complex was identified in the serum of the girl and the type of immunoglobulin light chain was determined for the first time. When encountering a child with hyperprolactinemia, pediatricians should take into account the possibility of macroPRL to avoid unnecessary investigation and/or treatment.
authors.affiliation: Division of Laboratory and Transfusion Medicine, Hokkaido University Hospital, Sapporo, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Nakano
authors.affiliation: Medical Laboratory Science, Faculty of Health Sciences, Hokkaido University, Sapporo, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Moriyama
authors.affiliation: Division of Laboratory and Transfusion Medicine, Hokkaido University Hospital, Sapporo, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Yasuda
authors.affiliation: Division of Laboratory and Transfusion Medicine, Hokkaido University Hospital, Sapporo, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Shibuya
authors.affiliation: Department of Pediatrics, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Tajima
authors.affiliation: Division of Laboratory and Transfusion Medicine, Hokkaido University Hospital, Sapporo, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Shigematsu
authors.affiliation: Division of Laboratory and Transfusion Medicine, Hokkaido University Hospital, Sapporo, Japan. Electronic address: shimizch@med.hokudai.ac.jp.
authors.forename: Chikara
authors.initials: C
authors.lastname: Shimizu
mesh_terms: D002648:Child; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D047468:Immunoprecipitation; D011388:Prolactin / Q000097:blood* / Q000276:immunology*
chemical_list: D007074:Immunoglobulin G; C060678:prolactin, polymeric; D011388:Prolactin
keywords: Hyperprolactinemia; IgG-κ-type autoantibody; Macroprolactin