A one and a half month old girl is referred to the paediatric clinic for a right pelvic kidney and a white tuft of hair in the frontal region.

She is from the first pregnancy of a healthy mother. The pregnancy was controlled without incident, with normal ultrasound scans except for the right pelvic kidney. Vaginal delivery, instrumented at 38 weeks gestational age. Birth weight 2320 grams, Apgar 10/10. Bilateral correct otoemissions.
Family history: white parents, healthy mother aged 25 years, healthy father aged 36 years, except for acromic spots in the middle third of both thighs, without having been diagnosed with any disease. Other family history is unknown.
The patient is asymptomatic; her bowel rhythm and diuresis are normal. Physical examination reveals a tuft of white frontal hair and a triangular-shaped acromic macule on the frontal region. There are no other skin lesions. The rest of the examination is normal, with psychomotor development so far normal.
Piebaldism is clinically suspected, but additional tests are requested to check for ophthalmological anomalies and deafness, which must be absent to confirm the clinical diagnosis of piebaldism. Ophthalmological assessment ruled out ocular lesions and auditory evoked potentials were performed, which were normal.
Abdominal ultrasound confirmed the presence of a right pelvic kidney with no other abnormalities.
An analytical study (blood count and chemistry) was requested, which was normal, and a genetic study for mutation of the KIT gene (OMIM 164920) (4q12), which was negative. A heterozygous variant in the KIT gene of unknown clinical significance [c.2509G>A;(p.Ala837Thr)] was detected (also negative in the father).