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Palmoplantar keratoderma with tonotubular keratin Andrea Wevers, MD, Andreas Kuhn, MD, and Gustav Mahrle, MD Kg)ln, Federal Republic of Germany

A 61-year-old man with palmoplantar keratoderma with an unusual tonotubular keratin is reported. The histologic findings, genetic transmission, and clinical course were similar to epidermolytic palmoplantar keratoderma (Voerner type), but keratinocytes ultrastructurally displayed a tonotubular cytoskeleton, which has not been previously described, instead of a tonofilamentous one. Electrophoretically, we found no difference in the keratin pattern of normal plantar skin, skin in palmoplantar keratoderma of Voerner, and that of our patient's skin. Therefore the tubular keratin most likely formed as a result ofa posttranslational change of keratin polymerization. (J AM AcAr9 DERMA'roLl991;24:638-42.)

The hereditary palmoplantar keratodermas (PPKs) are a heterogenous group of disorders char- acterized by hyperkeratosis of the palms and soles. They are distinguished by further clinical charac- teristics, associated abnormalities, and modes of inheritance) -3 PPK of Voerner, as does the Unna- Thost type, belongs to the diffuse PPKs with the autosomaldominant inheritance pattern and without any associated symptoms. It can be differentiated from other PPKs by the presence of granular degeneration in the malpighian layer (epidermolytic hyperkeratosis), which is exclusively found in PPK of Voerner. 4- t 2 More than 50 case reports have been published (for review see references 11 ~and 12), and a few electron microscopic studies have been performed. 6-9 This is the first report to differ from previous ones in its electron microscopic findings. Our preliminary report 13' 14 has now been extended and completed with immunostaining and electrophoretic analysis of the keratins.

CASE REPORT

A 61-year-old man had diffuse hyperkeratotic lesions on the palms and soles. It began a few days after birth, increased in severity during the first years of childhood, and has been stable since. On clinical examination the patient had a diffuse, yellowish, irregular palmoplantar keratosis, demarcated by a thin, erythematous rim strictly limited to the palms and soles (Fig. 1). Family history re- vealed that 18 of 40 members of the patient's family were similarly affected and indicated an autosomal dominant trait of inheritance (Fig. 2).

From the Department of Dermatology, University of Krln. Reprint requests: Andrea Wevers, MD, Department of Dermatology,

University of K6ln, Joseph-gtelzmann-Strasse 9, 5000 KSln 41, FRG.

16/4/19178

638

Fig. 1. Diffuse plantar keratosis.

MATERIAL AND METHODS

Histologic, electron microscopic, and electrophoretic investigations were performed on biopsy specimens of plantar epidermis. Plantar epidermis of a woman with PPK of Voerner, plantar epidermis of a healthy male vol- unteer, and skin from the leg of a woman with bullous congenital ichthyosiform erythroderma served as con- trois.

Light microscopy. Routine histologic staining and im- munostaining with a rabbit polyclonal antiserum to human keratin (Dakopatts, Glostrup, Denmark) were performed with the peroxidase-antiperoxidase technique.

Electron microscopy. For immunoelectron microscopy Lowicryl K4M (Lowi, Waldkraiburg, W. Germany)

Volume 24 Number 4 April 1991 Palmoplantar keratoderma with tonotubular keratin 639

Fig. 2. Pedigree of patient. Blackened squares and circles represent affected males and fe- males. Arrow denotes proband. Pedigree indicates autosomal dominant trait of inheritance.

Fig. 3. Photomicrograph of palmar epidermis demonstrates orthohyperkeratosis and vac- uolization of cells in granular and prickle cell layer. (Antikeratin-peroxidase-antiperoxidase stain; X160.)

Fig. 4. Photomicrograph of specimen from sole shows granular degeneration. (Hematox- ylin-eosin stain; •

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Fig. 5. Electron micrograph of stratum granulosum. Longitudinal and transverse cut of tonotubular keratin. (x 19,500.)

Fig. 6. Immunoelectron micrograph of tonotubules. Staining with antikeratin and second antibody labeled with 5 nm gold particles demonstrate their keratinous character. (X48,000.)

embedding a t - 35 ~ C was performed. 15 Ultrathin sections were stained with the same antikeratin antibody as for light microscopy and were incubated with goat antirab- bit immunoglobulin labeled with 5 nm gold particles (GAR-G5, Janssen Biochimiea, Beerse, Belgium) for 2 hours.

Electrophoresis. Cytoskeleton proteins were prepared from mechanically separated epidermis by exhaustive extraction.I ~ Keratins were separated by two-dimensional gel electrophoresis, first-dimension nonequilibrium pH gradient electrophoresis, according to O'Farrell et al., 17 and by second-dimension sodium dodecyl sulfate-poly- acrylamide gel electrophoresis, according to Laemmli, 18 and stained with Coomassie blue.

RESULTS

Light microscopy. The specimen of plantar epi- dermis showed a compact orthohyperkeratosis, hy- pergranulosis, acanthosis, and granular degenera- tion with large clumpy and small irregularly shaped keratohyalin bodies (Figs. 3 and 4). In and above the rete ridges epidermal cells were vacuolated and al- ternated with nonvacuolated cells, mostly in the su- prapapillary epidermis. A slight perivascular lym- phohistiocytic infiltrate was present.

Electron microscopy. Ultrastructural examina- tion revealed a unique alteration of the cytoskeleton. Instead of 10 nm broad tonofilaments, keratinocytes

Volume 24 Number 4 April 1991 Pahnoplantar keratoderma with tonotubular keratin 641

displayed tonotubuli with an external diameter of 43 nm (Fig. 5). As tonofilaments, tonotubuli were associated with keratohyalin and desmosomes. They were bundled or individually arranged within the cytoplasm, already present in the lower prickle cell layers. Besides these cells, a few cells existed in the suprapapillary epidermis retaining normal tonofila- merits. Cells containing tonotubules did not display tonofilaments and vice versa. Staining with antiker- atin showed that the tubular structures were labeled with gold particles, demonstrating their keratinous character (Fig. 6). In the controls, only tonofila- merits were observed.

Eleetrophoresis. The keratin pattern of plantar epidermis as indicated by two-dimensional gel elec- trophoresis (Fig. 7, a) showed the basal keratins 5 (58 kd) and 14 (50 kd), the differentiation keratins 1, 2 (67 kd, 65.5 kd, respectively), and 10 (56.5 kd), and the expression of the palmar and plantar specific keratin 9 (64 kd). In addition, proliferation keratins 6 (56 kd), 16 (48 kd), and 17 (46 kd) were found. In normal plantar epidermis the latter keratins were present only in small amounts (data not shown). In PPK of Voerner (Fig. 7, b) and PPK with tonotubu- lar keratin (Fig. 7, a) the anaounts of proliferation keratins were increased. Qualitatively and quantita- tively, no difference was detected in the keratin pat- tern between PPK of Voerner and PPK with tono- tubular keratin.

DISCUSSION

Hereditary epidermolytic PPK was first described by Voerner 4 in 1901. The clinical, genetic, and his- tologic features of the cases reported 512 are similar to those of the case we report. The only difference was that in our case, instead of 10 nm tonofilaments, tonotubuli with an external diameter of 43 nm were expressed. Such tonotubular keratin has not been reported in cases of PPK of Voerner. 69

Tubulofibrillar structures in PPK were mentioned by Anton-Lamprecht and Werner. 2~ They re- ported a case of PPK with the same kind of tubular keratin we observed. However, their case did not display light microscopic features of epidermolytic hyperkeratosis. Tubular structures were also discov- ered in Richner-Hanhart syndrome but with a smaller diameter (20 to 40 nm). 22 The channel walls seemed to be composed of identical elements-- probably tonofilaments--arranged in rotational symmetry. The authors proposed a biochemical model of noncovalent, cross-linked tonofilaments

5~

R

2~

b

Fig. 7. Keratin pattern of PPK with tonotubular kera- tin (a) and PPK of Voerner (b) as revealed by two-dimen- sional gel electrophoresis (first-dimension nonequilib- rium pH gradient electrophoresis, second-dimension, (b). sodium dodecyl sulfate--polyacrylarnide gel electrophore- sis). Gels were stained with Coomassie blue. Numerals denote human cytokeratin polypeptides according to Moll et al. 19 Brackets enclose isoelectric variants of same polypeptide; arrowheads denote residual amounts of very stable keratin complexes.

resulting from increased intracellular levels of L- tyrosine.

In contrast to Richner-Hanhart syndrome, nor- mal L-tyrosine blood levels were found in our case and in Anton-Lamprecht and Werner's case. No alterations in other amino acids in our patient were found.

Two-dimensional gel electrophoresis revealed that in addition to the differentiation keratins 1, 2, and 10, usually expressed in the suprabasal epidermis, keratin 9 was also found. The enhanced expression of keratin 9 in palms and soles is related to the mor- phogenesis of these areas. 16, 23 Compared with nor- mal plantar epidermis, in PPK of Voerner and in PPK with tonotubular keratin, increased amounts of

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the proliferation keratins were expressed. This is in agreement with the findings of other authors, z' 24 who reported that the mitotic index of the lesional epidermis in PPK of Voerner was two to six times greater than that of normal epidermis. There was no difference in the keratin pattern between PPK with tonotubular keratin and PPK of Voerner. Therefore it seems most likely that the tubular keratin is not due to an altered keratin pattern but is rather a posttranslational change in keratin polymeriza- tion.

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