Hemihypertrophy with hemimegalencephaly associated with type 1b (broad pattern) pigmentary mosaicism

Dear Editor,

Pigmentary mosaicism represents patterns of pigmentation in the skin and is observed with the defects of the neurological and musculoskeletal systems.^[1] Hemimegalencephaly is the enlargement of one hemisphere of the brain that may occur with neurocutaneous syndromes.^[2] A 2.5-year-old girl presented with developmental delay and right focal seizures from 7 months of age. On examination, she was found to have normal head circumference (47 cm), multiple hypopigmented streaky macules along the lines of Blaschko-type 1b: Broad pattern on the trunk and upper and lower limbs, hypertrophy of the right upper and lower limb [Figure 1]. The magnetic resonance imaging brain showed left hemimegalencephaly [Figure 2].

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Figure 1:

Multiple streaks of hypopigmentation along the lines of Blashcko present on the trunk, upper and lower limbs (arrows).

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Figure 2:

Brain magnetic resonance imaging-T2W (a) and fluid-attenuated inversion recovery (b) showing hypertrophy of the left cerebral hemisphere (arrows).

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Hemimegalencephaly with skin lesions is also seen in linear epidermal nevus syndrome, neurofibromatosis, Proteus syndrome, and Klippel–Trenaunay syndrome. The classical cutaneous lesions along Blaschko lines are helpful to differentiate them. Pigmentary mosaicism should be suspected in any child presenting with refractory focal seizures, hemihypertrophy with classical skin findings and hemimegalencephaly.