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What's the Diagnosis?

December 2018

Visual Diagnosis

Kristin Johansen, MD |General Pediatrics, Children's Mercy | Clinical Assistant Professor of Pediatrics, UMKC

A 4-year-old male presents to clinic for a well child visit. He has been doing well overall, but parents are concerned about discoloration on the right side of his abdomen that has been present since birth. The area has not changed since that time and is not bothersome to the patient.  He has been growing and developing as expected with no previously diagnosed medical problems.

Which of the following would be the most appropriate initial management?

A.     Complete a thorough history and physical to evaluate for associated anomalies

B.     Provide reassurance that rash will resolve spontaneously

C.     Initiate hotline for child physical abuse

D.     Prescribe topical steroids

The correct answer is A.

The skin lesion is most consistent with pigmentary mosaicism.

Pigmentary mosaicism is characterized by hypopigmentation and/or hyperpigmentation following the lines of Blaschko. Distribution is typically in a block-like, whorled, streaked or linear pattern and respects the midline. It is also referred to as hypomelanosis of ito, Blaschkoid dyspigmentation, linear and whorled nevoid hypermelanosis and segmental pigmentation disorder. It is caused from a post-zygotic mutation of skin cells effecting melanin production and is most often sporadic. The exact prevalence is unknown and can be seen in both sexes and all races.1  

Most commonly, the lesions are apparent at birth but may not be noted until later in childhood depending on the baseline skin pigmentation of the patient.2  The condition can be associated with extracutaneous manifestations but is generally benign and isolated to the skin.  The most common extracutaneous manifestions are neurologic and musculoskeletal (i.e., developmental delays and digit abnormalities).  These associations are seen in less than 30 percent of cases and are often apparent in early infancy.3  The diagnosis can be made clinically but dermatology referral can be made if diagnosis is in question.  Other subspecialists should be involved if extracutaneous manifestations are noted.  


  1. Mosaicism and Linear Lesions. In Dermatology (4th ed., pp. 1004-1025).  Bolognia J, Schaffer J and Cerroni L. (2018).
  2. Pediatric Dermatology A Quick Reference Guide (3rd ed.). American Academy of Pediatrics. Mancini AJ, Krowchuk DP. (2016).
  3. Analysis of 36 Cases of Blaschkoid Dyspigmentation: Reading Between the Lines of Blaschko. Cohen J, Shahrokh K, Cohen B. (2014). Pediatric Dermatology, 31(4), 471-476