Lumbosacral hypertrichosis as a cutaneous manifestation of dysraphism

A 11-year-old girl presented with hypertrichosis in the lumbosacral region, which has been present since birth. Right after birth, the girl underwent surgical intervention for spina bifida with no neurological impairment. On clinical examination, a circumscribed collection of terminal hair is observed on nonpigmented skin in the lumbar spine region (Figure 1a). Skin biopsy was performed, and histologic analysis revealed only a few scattered melanocytes in the basal epidermis and a characteristic dense aggregation of hair follicles (Figure 1b).

Lumbosacral hypertrichosis, also known as ‘Faun's tail’ after the Italian deity, is a classic sign of dysraphism.¹ This generic term describes pathologic conditions related to improper closure of the caudal neuropore and encompasses all conditions associated with spina bifida occulta, traction band or diastematomyelia.^{1, 2} The division between the neuroectoderm and the epithelial ectoderm takes place between the third and fifth week of fetal development, commencing along the posterior midline.² This separation may remain incomplete at various stages, resulting in potential defects in the skin, vertebrae, spinal cord and/or central nervous system, sometimes symptoms may not appear until the child is a toddler or older.³ Hence, in cases of lumbosacral hypertrichosis, consideration should be given to an underlying spinal abnormality, prompting subsequent relevant investigations. The most important differential diagnosis is congenital hairy nevus.

The authors confirm contribution to the paper as follows: Clinical case collection: Sarah Preis. Draft manuscript preparation: Sarah Preis. Manuscript review and proof-reading: Christina Schnopp. All authors reviewed the results and approved the final version of the manuscript.

The authors declare no conflict of interest.

The parents/guardians of minor patients have given written informed consent for their child's participation in the study, as well as for the use of their child's deidentified, anonymized, aggregated data and case details (including photographs) for publication. Ethical Approval: not applicable.