Woolly hair nevus in a toddler.

Woolly hair nevus (WHN) is a rare hair condition, with only a few cases reported. It affects young children of both sexes and currently, there is no available treatment. When WHN is associated with an epidermal nevus, further study is required to rule out ophthalmologic and neurologic abnormalities. We present the case of a Chilean 3-year-old healthy girl with a WHN, with no other clinical findings. This case illustrates a WHN in which the benign and chronic nature of the disease must be advised to the parents in order to prevent further concerns.

INTRODUCTION

Woolly hair (WH) has three characteristics: Decreased diameter, tightly coiled hair and oval form at transversal section. The hair looks fine, curled and hypopigmented.

When WH covers the entire scalp, it can be inhered in a dominant or recessive mode. In those cases, it can be an isolated feature or associated with extracutaneous abnormalities. When WH covers a part of the scalp, it is called woolly hair nevus (WHN).

Woolly hair nevus is a rare, non-hereditary variant, and begins at a young age. To our knowledge, this is one of the first reports of a Chilean child with a WHN.[12]

CASE REPORT

We present a 3-year-old healthy girl, whose mother was concerned about recent hair changes. The patient had no personal or family history of cutaneous diseases. At physical exam, the girl had a phototype II skin, normal teeth and nails. The back of the scalp revealed a well-circumscribed patch of kinky, curly light blonde hair. The rest of the physical exam was normal. Dermoscopy was not performed at the time.

Woolly hair nevus was diagnosed. The parents were counseled about the benign and chronic nature of this lesion. Ophthalmologic evaluation was recommended, but the parents of the patient refused. No further studies were performed [Figures 1 and 2].

Figure 1

Frontal view of the patient. In the back of the scalp, a portion of the hair looks kinky, curly and lighter in color

Figure 2

Lateral view. Well defined patch of wool

DISCUSSION

WH is a woolly textured, often lighter hair, that it is difficult to comb, but is not fragile and is not a form of hypotrichosis. Hutchinson classified WH into three types: A hereditary form of generalized WH of autosomal dominant inherence, a familial form of autosomal recessive inherence and WHN. WHN is a non-hereditary form of WH that equally affects both sexes and has an unknown pathophysiology.[3]

Woolly hair nevus appears during the first 2 years of life, as a well-circumscribed patch of kinky, very curly lighter hair, that may darken and become less curly over the years. Recent reports have pointed that it also might be noticed earlier in young babies as congenital patchy area of alopecia, which later evolves to a WHN.

The use of dermoscopy has proven to be useful, especially when other diagnoses are considered. Patil et al., described the presence of hair shafts with a “crawling snake” appearance, with short wave cycles, and broken hairs.[45] Electron microscopy has shown signs of cuticle wear and tear. In Chile, this technique is difficult to perform, mostly because there are few devices in the country; most of them used for research purposes.

Woolly hair nevus grows parallel to the child and remains stable throughout adult life. Extracutaneous abnormalities have been described, especially when the WHN is associated with an epidermal nevus, constituting an epidermal nevus syndrome. In those cases, it is important to rule out further compromise of the ophthalmologic, nervous and cardiac systems.[236]

Until date, there are no effective treatments for this condition.[17] Therefore, is important to advice and counsel the parents about the benign nature of this disease, especially when it is present as an isolated feature.

The majority of WHN cases have been described in Europe and the US. Currently, there are only a few case report of WHN in South America. One case was reported in Argentina and two cases were described in Brazil, both of them with features of epidermal syndrome.[8910] In Chile, there is only one case described, but in this patient the WHN was associated with an epidermal nevi.[11]

We present this case as one of the few cases of WHN described in South America.