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I-Cell Disease (Mucolipidosis Type II) Workup

  • Author: Karl S Roth, MD; Chief Editor: Luis O Rohena, MD  more...
Updated: Aug 21, 2015

Laboratory Studies

Biochemical diagnosis can be made in the following ways:

  • N -acetylglucosaminyl-1-phosphotransferase activity can be measured in WBCs or in cultured fibroblasts.
  • Various lysosomal enzyme activities can be measured in serum and in cultured fibroblasts. The activities of beta-hexosaminidase, iduronate sulfatase, and arylsulfatase A are deficient in cultured fibroblasts, but their serum levels are 10-20 times the reference range. Assays for lysosomal enzymes in leukocytes are not reliable because of mannose-6-phosphate–independent targeting pathways.
  • Dried blood spot screening methodology has been reported. [23]

Imaging Studies


The characteristic bone changes are similar to those observed in the mucopolysaccharidoses. There may be fractures, bone rarification, and other findings leading to confusion with rickets.[7]

The classic finding is dysostosis multiplex, with a cloaking appearance of the long tubular bones, anterior beaking and wedging of the vertebral bodies, widening of the ribs, proximal pointing of the metacarpals, and bullet-shaped phalanges.

Brain imaging

Brain imaging is not necessary to diagnose I-cell disease, although it is often performed during evaluation of developmental delay.

MRI and CT scan findings can be variable and nonspecific and may not aid in the diagnosis. Reported MRI and CT scan findings include completely normal scans with normal myelination, cerebral atrophy, and nonspecific white matter changes.


Histologic Findings

A unique finding in I-cell disease is the presence of numerous intracytoplasmic inclusions in cells of mesenchymal origin that are observed on electron microscopy. These inclusions are membrane-bound vacuoles filled with fibrillogranular material. The contents of these vacuoles have not been well characterized; however, they appear to contain various lipids, mucopolysaccharides, and oligosaccharides.

Contributor Information and Disclosures

Karl S Roth, MD Retired Professor and Chair, Department of Pediatrics, Creighton University School of Medicine

Karl S Roth, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American College of Nutrition, American Pediatric Society, American Society for Nutrition, American Society of Nephrology, Association of American Medical Colleges, Medical Society of Virginia, New York Academy of Sciences, Sigma Xi, Society for Pediatric Research, Southern Society for Pediatric Research

Disclosure: Nothing to disclose.


Margaret M McGovern, MD, PhD Professor and Chair of Pediatrics, Stony Brook University School of Medicine

Margaret M McGovern, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Society of Human Genetics

Disclosure: Nothing to disclose.

William B Rizzo, MD Professor, Department of Pediatrics, University of Nebraska Medical Center

William B Rizzo, MD is a member of the following medical societies: American Society of Human Genetics, Society for Inherited Metabolic Disorders

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Margaret M McGovern, MD, PhD Professor and Chair of Pediatrics, Stony Brook University School of Medicine

Margaret M McGovern, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Society of Human Genetics

Disclosure: Nothing to disclose.

Chief Editor

Luis O Rohena, MD Chief, Medical Genetics, San Antonio Military Medical Center; Assistant Professor of Pediatrics, Uniformed Services University of the Health Sciences, F Edward Hebert School of Medicine; Assistant Professor of Pediatrics, University of Texas Health Science Center at San Antonio

Luis O Rohena, MD is a member of the following medical societies: American Academy of Pediatrics, American Chemical Society, American College of Medical Genetics and Genomics, American Society of Human Genetics

Disclosure: Nothing to disclose.

Additional Contributors

Edward Kaye, MD Vice President of Clinical Research, Genzyme Corporation

Edward Kaye, MD is a member of the following medical societies: American Academy of Neurology, Society for Inherited Metabolic Disorders, American Society of Gene and Cell Therapy, American Society of Human Genetics, Child Neurology Society

Disclosure: Received salary from Genzyme Corporation for management position.


The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous author Grace Lee, MD, to the original writing and development of this article.

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Profile view of 3-year-old with I-cell disease. Growth ceased more than one year earlier. Note small orbits, proptotic eyes, full and prominent mouth caused by gingival hypertrophy, short and broad hands, stiffening of small hand joints, prominent abdomen with umbilical hernia, and limited extension of the hips and knees.
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