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Abstract

Ectodermal dysplasias (ED) are a rare group of genodermatoses affecting tissues of ectodermal origin namely: hair, nails, teeth, and sweat glands. Pure hair, nail ectodermal dysplasias (PHNED) are very rare, and involve only hair and nails, while other ectodermal structures are intact. To date only 20 cases have been reported inthe world literature. We report two cases of PHNED in a 15 years old Yemeni boy, and his 2 months old sister, who were born with total absence of hairs and dystrophic 20 nails. All other family members were not affected.

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Keywords

Skin; Hair; Nail; Ectodermal dysplasia

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Introduction

Pure hair-nail ectodermal dysplasias (PHNED) are very rare subtype of Ectodermal dysplasias (ED), involving only hair and nails, while other ectodermal structures (teeth and sweat glands) are intact. The first case of ED was reported by Thurnam in 1848, while Weech coined the term ED in 1929 [1,2]. To date only 20 cases of PHNED have been reported worldwide

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Case 1

A 15 years old Yemeni boy presented with total alopecia involving the scalp, brows, and lashes and distal 20 nail dystrophy since birth (Figure 1a). On close inspection of the scalp, small black hairs can be seen within the hair follicles (Figure 1b). All 20 nails were distally dystrophic and sloped (Figures 1c and 1d). Teeth and sweat glands were not affected. The histological examination of the scalp showed severely reduced number of structurally disorganized hair follicles (Figure 1e). The patient was otherwise healthy. His parents and his 11, 9 years old brothers, and 5 years old sister, were not affected, suggesting an autosomal recessive mode of inheritance (Figure 2).

  

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Case 2

The two months old sister of case 1, presented with similar albeit milder manifestations as her brother (Figures 3a-3d).

 

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Discussion

EDs are rare group of genodermatoses affecting tissues of ectodermal origin namely: hair, nails, teeth, and sweat glands. Freire-Maia and Pinheiro proposed the first classification system for ectodermal dysplasias in 1982, with additional updates in 1994 and 2001 [3,4]. PHNED are very rare subtype of ED. They can be inherited as autosomal recessive and autosomal dominant pattern, with highly variable clinical expression [5,6]. A summary of clinical and genetic finding in previously reported cases is shown (Table 1). Affected individuals are usually born devoid of hairs of the scalp, brows, and lashes. All 20 nails are distally dystrophic and sloping, and they never need to be trimmed. To date only 20 cases of PHNED have been reported worldwide. Mutation in the KRT85 gene was found in some patients, while mutations either in the COXC13 or KRT74 genes were found in others [7-9]. Keratin 85 and keratin 74 belong to keratin type II, while COXC13 is a transcription regulator of keratin and keratin-associated protein genes. Keratins are important intermediate filaments of keratinocytes of the hair and nails that give them the ability to resist mechanical trauma. They are classified into two types: type I, having their genes on chromosome 17, and type II, having their genes on chromosome 12.

The clinical findings in our two cases are very similar to the case described by Naeem et al. who found a mutation in the hair matrix and cuticle keratin KRTHB5 gene [10]. The histopathological findingsof the scalp biopsy are similar to the case published by Lin et al. [9]. A genetic analysis would be of great help to determine the causative mutation in our case, but unfortunately this sophisticated tool is not available in most of the developing countries.

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Conclusion

The two reported cases were diagnosed based on clinical findings, which were exactly the same as of the cases reported by Naeem et al. supported by the histopathological findings of the scalp biopsy, which were similar to the case described by Lin et al. We hope that a genetic analysis could be available in near future in all developing countries, in order to confirm the underlying mutation in our two cases.