Nail abnormalities are a common feature in most subtypes of epidermolysis bullosa (EB), and they recently have been included among the criteria for scoring EB severity. Trauma undoubtedly contributes to the development of nail dystrophy, and for this reason the great toenails often are affected more severely. The nail abnormalities may be the first or the only symptom of EB. Nail abnormalities observed in EB are not specific or pathognomonic, as they result from nail bed and matrix scarring. The spectrum of clinical severity is large, and nail abnormalities may cause severe disability or just be a mild cosmetic problem. This article reviews the nail abnormalities observed in EB.
Although the anatomy of the nail apparatus is different from that of the skin, the antigenic expression of basement membrane zone (BMZ) components in the normal matrix, nail bed, proximal nail fold, and hyponychium is similar to that of normal skin. In addition, there are no differences in the antigenic composition of the BMZ between the different portions of the nail matrix. Nail expression of all the target antigens found in the normal nonappendage basement membrane explains why nail involvement is a feature of most epidermolysis bullosa (EB) subtypes.
Even though the absence or presence of nail changes at birth should not be used as absolute criteria for differential diagnosis between different subtypes of EB, nail involvement recently has been included among the criteria for scoring EB severity, as early nail dystrophy and loss are correlated with disease severity and progression, particularly in junctional epidermolysis bullosa (JEB) and recessive dystrophic epidermolysis bullosa (RDEB).
Trauma undoubtedly contributes to the development of nail dystrophy, and for this reason, the great toenails more often are affected severely.
The nail abnormalities may be the first or the only symptom of EB. In fact they may precede the development of skin blistering as in the late-onset JEB ( Fig. 1 ) and pretibial DEB, or be an isolated finding as reported in some families with dominant dystrophic EB (DDEB) ( Figs. 2 and 3 ).
Nail involvement is uncommon in localized EB simplex (EBS) and is not a feature of EBS migratory circinate or EBS with pyloric atresia ( Table 1 ).
|Major Type of EB||Subtypes||Frequency of Nail Involvement||Nail Signs|
|EBS superficialis AD||70%||Dystrophic nails|
|Lethal acantholytic EBS AR||100%||Nail loss|
|Plakophilin deficiency AR||100%||Thickened dystrophic nail|
|EBS localized AD||Uncommon||Blistering may cause onycholysis and onychomadesis, with normal regrowth or thickened dystrophic nails|
|Dowling-Meara AD||>75%||Onychomadesis, pachyonychia, onychogryphosis, pincer nails or absent nails|
|EBS other generalized AD (previously called Koebner)||14%||Onychomadesis with normal regrowth, pachyonychia, thickened great toenail|
|AR EBS||Hyperkeratotic nails, horizontal ridging, anonychia|
|EBS migratory circinate||Absent||None|
|EBS with mottled pigmentation||Uncommon||Dystrophic nails, small toenail|
|EBS with muscular dystrophy||50%||Onychomadesis, pachyonychia, onychogryphosis, pincer nails, anonychia|
|EBS with pyloric atresia||Absent||None|
|JEB||Herlitz AR||>75%||Pachyonychia, exuberant granulation tissue, nail erosion, anonychia|
|Non-Herlitz AR (generalized and localized)||>75%||Anonychia, dystrophic nails|
|With pyloric atresia AR||Nail thinning and atrophy or absent nails|
|Inversa JEB||>50%||Dystrophic or absent nails|
|Late-onset JEB||Onycholysis, nail loss, Beau’s lines|
|LOC syndrome||100%||Nail thickening, nail erosions with granulation tissue, anonychia|
|DDEB generalized||>75%||Nail thickening, onychogryphosis, anonychia, pseudosyndactyly|
|RDEB severe generalized||>75%||Anonychia, pseudosyndactyly|
|RDEB generalized other||>75%||Dystrophic or absent nails|
|Acral DDEB and RDEB||>75%||Nail thickening anonychia|
|Pretibial DDEB and RDEB,||>75%||Nail thickening|
|Pruriginous DEB, AD or AR||>75%||Nail thickening, anonychia|
|DDEB nails only||100%||Pachyonychia, thickened dystrophic nails anonychia|
|DEB-BDN||25 – 50%||Nail thickening, anonychia pseudosyndactyly|
|RDEB inversa||>75%||Nail thickening|
|RDEB centripetalis||>75%||Dystrophic or absent nails|
|Kindler syndrome||AR||Nail dystrophy, parrot beak nail deformity, absent nails|