To the Editor: Neurofibromatosis type 1 (NF1) is an autosomal dominant, neurocutaneous disorder. In most cases, cutaneous pigmentary manifestations are the main diagnostic clue. NF1 is characterized by hyperpigmentation—café au lait macules (CALMs), skinfold freckling, and melanotic plexiform neurofibromas. However, hypopigmented lesions have received little attention in patients with NF1. Riccardi1Riccardi V.M. Neurofibromatosis and Albright's syndrome.Dermatol Clin. 1987; 5: 193-203Abstract Full Text PDF PubMed Google Scholar described the presence of hypopigmented macules (HMs) in approximately 2% to 3% of patients with NF1 in 1987. Studies regarding the physiopathology of HM in NF1 are lacking. This study aimed to characterize the prevalence of HMs in our pediatric patients diagnosed with NF1. A case-control prospective study design was used to compare the prevalence of HMs in 108 patients diagnosed with NF1 (younger than 18 years) and 137 healthy age-matched control individuals. All patients included in the cases cohort had a confirmed diagnosis of NF1. We required a third National Institutes of Health criterion or genetic testing in children who exclusively showed CALMs and skinfold freckling. The patients were enrolled from October 2014 to January 2017. We also assessed the number, location, size, and morphology of HMs in our patients. Well-circumscribed lesions, those with early onset in life, and stable hypomelanosis were considered HMs. Patients with postinflammatory hypomelanosis and other possible causes of hypopigmentation as well as vitiligo or nevus anemicus (NA) were excluded. All HMs became erythematous after rubbing, unlike NA. All participants signed informed consent. We observed that 13.9% (n = 15) of patients showed HMs. In the control group 4.4% (n = 6) children presented with HMs. The prevalence of HMs in the cases group was significantly higher than in the control group (Pearson chi-square test P value = .008). Demographic and clinical characteristics are shown in Table I. The HM sizes ranged from 0.5 to 9 cm, and all presented with well-defined or sharp margins (Fig 1 and Supplemental Fig 1; available via Mendeley at https://doi.org/10.17632/6w3g76nyxr.2). Parents recalled the presence of HMs from birth in 4 (22.2%) children.Table IDemographic and clinical characteristicsClinical featuresPatients with NF1 (N = 108)Control individuals (N = 137)HMs, n (%)15 (13.9)6 (4.4)Age when HMs first noticed, y Mean4.24.7 Range0-103-13Sex, n (%)P = .132P = 1 Male9 (60)3 (50) Female6 (40)3 (50)Distribution Solitary, n (%)12 (80)6 (100) Range1-2 Mean ± SD1.2 ± 0.41Location, n (%) Thorax6 (40)3 (50) Legs5 (33.3)1 (16.6) Abdominal3 (20)0 Arms2 (13.3)1 (16.6) Lumbar1 (6.6)1 (16.6) Neck1 (6.6)0Size, cm, n (%) <14 (22.2)2 (33.3) 1-513 (72.2)4 (66.6) >51 (5.6)0Morphology, n (%) Ash-leaf6 (33.3)0 Rounded5 (27.8)3 (50) Oval5 (27.8)3 (50) Polygonal2 (11.1)0HM, Hypopigmented macule; SD, standard deviation. Open table in a new tab HM, Hypopigmented macule; SD, standard deviation. Although CALMs are present in almost all patients with NF1, the prevalence of circumscribed hypomelanosis has not been characterized. The differential diagnosis for HMs included tuberous sclerosis complex (TSC) hypomelanotic macules, NA, vitiligo, pityriasis alba, postinflammatory hypopigmentation, and piebaldism. The simultaneous occurrence of NF1 and TSC in a single individual is extremely rare,2Samanta D. Bosanko K.B. Zarate Y.A. An infant with ash-leaf and café au lait spots: a case of double phakomatosis.Acta Neurol Belg. 2016; 117: 323-324Crossref PubMed Scopus (1) Google Scholar and our patients did not show other signs of TSC. The HMs observed in patients with NF1 fulfilled the Coupe clinical diagnostic criteria and could be considered nevus depigmentosus (ND).3Coupe R.L. Unilateral systematized achromic naevus.Dermatology. 1967; 134: 19-35Crossref Scopus (40) Google Scholar,4Kim S.K. Kang H.Y. Lee E.S. Kim Y.C. Clinical and histopathologic characteristics of nevus depigmentosus.J Am Acad Dermatol. 2006; 55: 423-428Abstract Full Text Full Text PDF PubMed Scopus (46) Google Scholar ND is the best characterized congenital, stable throughout life, well-circumscribed hypopigmented lesion.3Coupe R.L. Unilateral systematized achromic naevus.Dermatology. 1967; 134: 19-35Crossref Scopus (40) Google Scholar ND occurs in approximately 0.4% to 0.7% of infants,5Baselga E. Disorders of hypopigmentation.in: Schachner L.A. Hansen R.C. Pediatric Dermatology. 4th ed. Mosby Elsevier, Philadelphia, PA2012: 719-722Google Scholar so the HM prevalence in our series (13.9%) was higher than expected. Thus, our results suggest a statistical relationship between NF1 and HMs (P < .008). However, the pathophysiologic explanation of the higher prevalence of HMs in the NF1 population remains unknown. We conclude that HMs are a common finding in NF1. This finding could be either a coincidence or truly associated with NF1. Basic research investigations are needed to achieve a better knowledge of HM physiopathology.