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Pediatric Hypomelanosis of Ito Workup

  • Author: Camila K Janniger, MD; Chief Editor: Dirk M Elston, MD  more...
 
Updated: Jun 24, 2016
 

Laboratory Studies

Chromosomal analysis

Blood karyotyping is indicated, especially when systemic abnormalities are present.

Fibroblast karyotyping (sampling the dark and light skin) can reveal mosaicism but is not mandatory for diagnosis.

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Imaging Studies

Neuroradiological abnormalities are reported in at least one third of the patients. Because many of the lesions are dysplastic or neuroblastic migration abnormalities, MRI is more useful than CT scanning.

Increase in the T2 signal of white matter is one of the most common findings. White matter abnormalities are somewhat predictive of a poor neurological outcome.

Neuroblast migration includes heterotopia, pachygyria, and polymicrogyria. Heterotopia may be observed at the level of the basal ganglia or as a periventricular band. Some of the dysplastic lesions may be localized, and hemimegalencephaly is also visualized.

Cerebral atrophy can be unilateral or generalized. Cases of cerebral hemiatrophy and porencephaly are often associated with a history of perinatal hypoxia or low birth weight.

Other rare imaging associations include the following:

  • Noncommunicating hydrocephalus
  • Megacisterna magna
  • Arteriovenous malformation
  • Cerebellar hypoplasia (hemispheres and vermis)
  • Brainstem hypoplasia
  • Brain tumors: MRI rarely reveals brain tumors; thus, patients occasionally have abnormal MRI findings but are neurologically healthy.

Brain imaging in patients with hypomelanosis of Ito (HI) and medically refractory epilepsy: The area that generates seizures (zone of ictal onset) should be found using a prolonged video-EEG, single-photon emission computed tomography (SPECT) or positron emission tomography (PET), and high-resolution MRI. If resective epilepsy surgery is a serious consideration after the preliminary tests are done (video-EEG, SPECT or PET) and the zone of ictal onset could not be determined, the patient may need to undergo invasive EEG monitoring with subdural grids or strips.

Other imaging tests

Musculoskeletal abnormalities often require radiography for proper quantification. A CT scan of the chest may be necessary when mediastinal tumors are investigated.

Abdominal ultrasonography may be required for diagnosis of genitourinary anomalies such as single kidney and urethral duplication.

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Other Tests

In patients with seizures, an EEG is indicated to show focal discharges and slowing.

Most patients with cardiac anomalies require an ECG.

Perform a slit-lamp examination in patients with ophthalmologic abnormalities.

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Procedures

Biopsies of affected and nonaffected skin are sometimes indicated.

In select patients with cardiac anomalies, cardiac catheterization is recommended for proper diagnosis.

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Histologic Findings

Dihydroxyphenylalanine (DOPA) staining of the skin may reveal decreased size and number of melanosomes in hypopigmented areas. The melanocytes may be smaller and fewer, and their dendrites are short and sparse. Melanin incontinence (ie, melanin is absent in the epidermis but present in the deeper dermis) is not observed in patients with hypomelanosis of Ito. Histopathological alterations are not always typical; normal histology findings have been described in some cases. Neuropathological studies demonstrate polymicrogyria, disarray of cortical lamination, and heterotopic neurons in the white matter and giant cells.

Ultrastructural cutaneous studies may reveal normal-appearing basal and malpighian keratinocytes but a lack of melanosomes in the malpighian cells.[7] Melanosomes are dramatically reduced in the basal keratinocytes and appear small, single, or clustered and surrounded by a membrane. Melanocytic degeneration may be evident, and dendritic melanocytes contain various stages of nonmelanized premelanosome (stage II), partially melanized premelanosome (stage III), and, rarely, stage IV melanosomes. Unmyelinated axons of nerve-containing melanosomes may be seen at the dermoepidermal junction. Abnormal nerve termination has been observed in close relationship with basal keratinocytes, degenerated melanocytes, premelanosomes, and Langerhans cells.

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Contributor Information and Disclosures
Author

Camila K Janniger, MD Clinical Professor of Dermatology, Clinical Associate Professor of Pediatrics, Chief of Pediatric Dermatology, Rutgers New Jersey Medical School

Camila K Janniger, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Coauthor(s)

Marcio Sotero de Menezes, MD Clinical Associate Professor, Department of Neurology, Division of Pediatric Neurology, Seattle Children's Hospital, University of Washington School of Medicine; Director, Pediatric Neuroscience Center and Genetic Epilepsy Clinic, Swedish Neuroscience Institute

Marcio Sotero de Menezes, MD is a member of the following medical societies: American Academy of Neurology, American Epilepsy Society

Disclosure: Received salary from Novartis for speaking and teaching; Received salary from Cyberonics for speaking and teaching; Received salary from Athena diagnostics for speaking and teaching.

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.

Robert A Schwartz, MD, MPH Professor and Head of Dermatology, Professor of Pathology, Pediatrics, Medicine, and Preventive Medicine and Community Health, Rutgers New Jersey Medical School; Visiting Professor, Rutgers University School of Public Affairs and Administration

Robert A Schwartz, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, New York Academy of Medicine, American Academy of Dermatology, American College of Physicians, Sigma Xi

Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine

Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Additional Contributors

Kevin P Connelly, DO Clinical Assistant Professor, Department of Pediatrics, Division of General Pediatrics and Emergency Care, Virginia Commonwealth University School of Medicine; Medical Director, Paws for Health Pet Visitation Program of the Richmond SPCA; Pediatric Emergency Physician, Emergency Consultants Inc, Chippenham Medical Center

Kevin P Connelly, DO is a member of the following medical societies: American Academy of Pediatrics, American College of Osteopathic Pediatricians, American Osteopathic Association

Disclosure: Nothing to disclose.

References
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Hypomelanosis of Ito on the torso.
 
 
 
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