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 Table of Contents  
Year : 2022  |  Volume : 9  |  Issue : 2  |  Page : 137-138

Mosaic neurofibromatosis type 1 or segmental neurofibromatosis: what is in the name?

Department of Dermatology, Venereology and Leprology, Government Medical College and Hospital, Chandigarh, India

Date of Submission27-Oct-2020
Date of Decision01-Jan-2022
Date of Acceptance22-Feb-2022
Date of Web Publication12-Aug-2022

Correspondence Address:
Dr. Bhalla Mala
Department of Dermatology, Venereology and Leprology, Government Medical College and Hospital, Sector 32B, Chandigarh 160030
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/pigmentinternational.pigmentinternational_

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How to cite this article:
Shruti K, Ramu SS, Mala B. Mosaic neurofibromatosis type 1 or segmental neurofibromatosis: what is in the name?. Pigment Int 2022;9:137-8

How to cite this URL:
Shruti K, Ramu SS, Mala B. Mosaic neurofibromatosis type 1 or segmental neurofibromatosis: what is in the name?. Pigment Int [serial online] 2022 [cited 2022 Sep 28];9:137-8. Available from: https://www.pigmentinternational.com/text.asp?2022/9/2/137/353676


Segmental neurofibromatosis (SN) is a rare subtype of neurofibromatosis (NF) characterized by abnormal pigmentary changes and neurofibromas in segmental distribution. The term “segmental NF” refers to individuals who have manifestations of NF such as café-au-lait macules (CALM) or neurofibromas limited to one side of the body. Segmental NF was once strictly believed to be noninheritable, which no longer seems to hold true in view of reports of NF1 occurring in children of segmental NF patients.

An 11-year-old boy was brought with chief complaint of asymptomatic pigmented lesions over the body since 1 year of age. The lesions first appeared over the left side of abdomen and progressed to involve chest and neck over the same side [Figure 1]. There was no history of blurring of vision, seizures, hearing loss, gastrointestinal complaints, or any developmental delay. There was no history of similar lesions in any of the family members. General physical examination was normal with no skeletal, auditory, or ocular abnormality. On cutaneous examination, there were multiple, discrete well-circumscribed brownish macules and patches ranging from 0.5 to 3 cm in the largest diameter over abdomen, neck, and chest without crossing midline [Figure 2]. Axillary freckling was present. Nails, hair, and mucosae were normal. Magnetic resonance imaging of brain and abdominal ultrasound were normal. Considering the presence of multiple unilateral CALM and axillary freckling in the absence of neurofibromas, family history, and systemic involvement diagnosis of segmental NF was made.
Figure 1 Multiple well-circumscribed brownish macules, patches over abdomen, chest, and neck with sharp demarcation at the midline.

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Figure 2 Multiple light brown-pigmented macules over left axillae.

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The NF is a group of neurocutaneous syndromes characterized by abnormal skin pigmentation and tumors of the nervous system with autosomal dominant inheritance. NF1 is the classical form which shows genetic inheritability, whereas type V is SN which is a rare subset that occurs 10 to 20 times less frequently.[1] SN is defined as CALM and/or axillary freckling, and/or neurofibromas distributed in a single unilateral segment of the body, without midline crossing, family history, or systemic involvement.[2]

Recently, it has been suggested that SN is not a separate entity, but rather a localized phenotype caused by somatic mutation of NF1 gene as cases have been reported of patients with SN having offsprings with complete NF1 which have been explained on the basis of gonadal mosaicism. Thus mosaic NF1 is now considered a more appropriate term.[1]

The variable presentation of SN has been suggested to be due to a postzygotic somatic mutation on the NF1 gene present on chromosome 17 with the presentation depending on the timing of the mutation.[3]

These mutations also have potential for malignant nerve sheath tumor. Patients with neurofibromas and pigmentary changes have been associated with risk of malignancy.[4]

Recently, Legius syndrome has been described which is NF1-like syndrome characterized by multiple CALM with or without axillary freckling. It has an autosomal dominant inheritance.[5]

Thus, all individuals with mosaic NF1 should have a complete physical and family examination, workup including genetic analysis and counseling. Genetic testing should be carried out to confirm the diagnosis, for family planning, for prenatal, or preimplantation genetic diagnosis, and to prognosticate for tumors.[6] This could not be performed in this case due to nonavailability of the test in our institute. Which is a limitation. Counseling should take into account the fact that not much can be treatment of cutabeous signs, possibility of a full blown case of NF in the subsequent generation, and chances of malignancy in this patient. Thus, they should also undergo frequent screens to look for development of malignancy. In addition, for the sake of better classification and unified diagnosis, terms such as segmental NF may need to be abandoned and replaced by mosaic NF which may better reflect the conditions’ phenotype and association.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Ruggieri M, Huson SM. The clinical and diagnostic implications of mosaicism in the neurofibromatoses. Neurology 2001;56:1433-43.  Back to cited text no. 1
Sobjanek M, Dobosz-Kawalko M, MichajtowskiI Peksa R, Nowicki R. Segmental neurofibromatosis. Postep Derm Alergol 2014;6:410-2.  Back to cited text no. 2
Ticshert S, Naumann I, Stegmann E et al. Segmental neurofibromatosis is caused by somatic mutation of the neurofibromatosis type 1 (NF1) gene. Eur J Hum Genet 2000;8:455-9.  Back to cited text no. 3
Doherty SD, George S, Prieto VG, Gereshenwald JE, Juvic M. Segmental neurofibromatosis in association with a large congenital nevus and malignant melanoma. Dermatol Online J 2006;12:22.  Back to cited text no. 4
Sharma MK, Kumar R, Gupta S, Jain SK. Legius syndrome. Indian J Paediatric Dermatol 2018;19:86-8.  Back to cited text no. 5
Jindal R, Shirazi N, Rawat K. Hereditary segmental neurofibromatosis: a report of three cases in a family. BMJ Case Rep 2019;12:e228826.  Back to cited text no. 6


  [Figure 1], [Figure 2]


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