A 5-year-old Japanese boy presented to the dermatology department with multiple linear pigmentations on the arms and trunk. Linear brown verrucous papules on the left forearm were noticed at about 9 months after birth (Figure A), and nuchal pigment macules were recognized at 1 year old. Linear and whorled hyperpigmentation then appeared gradually on the patient's back, axilla, and chest (Figure B). There was no hyperkeratosis of the palms or soles. Woolly hair was observed locally on the scalp (Figure C). Other than the skin manifestations, the patient did not exhibit any other symptoms. Neither the patient's parents nor his sister had woolly hair or linear pigmentation. Histopathologically, a skin biopsy specimen on the axilla with linear pigmentation showed hyperkeratosis, hypermelanosis, acanthosis, and papillomatosis of the epidermis that was consistent with an epidermal nevus (Figure ). Genetic screening was conducted after obtaining written informed consent. Next-generation sequencing of the genomic DNA purified from the epidermis of the epidermal nevus enzymatically separated from the dermis using custom-targeted exome sequencing panels of the Haloplex target enrichment system. Sanger sequencing revealed an HRAS c.34G>A (p.G12S) mutation specifically in the epidermis but not in the dermis of the epidermal nevus and the blood (Figure ). Analyses of the mRNA determined the identical HRAS mutation in the hair roots of the woolly hair but not of the straight hair (Figure ). Echocardiography and abdominal ultrasound performed after genetic diagnosis showed no abnormal findings.
A 5-year-old girl with a patch of kinky hair in the right parietal region, which had been present since the age of 4 months and different colored eyes since birth referred to our clinic []. The underlying scalp was normal. The affected hair appeared smaller in diameter and lighter than the normal hair color and no structural hair abnormalities were detected under the light microscope. She had slightly hyperpigmented linear lesions mostly marked on the anterolateral of the right arm with midline pectoral and abdominal extension []. The right eye was diffusely brown, and the left was green []. No ophthalmologic, cardiac, neurological or skeletal abnormalities were observed. Nails and teeth were normal. The patient was diagnosed with a woolly hair nevus of the right parietal scalp associated pigmented demarcation lines and heterochromia iridis.