Mal de Meleda without mutations in the ARS coding sequence

ARTICLE

Mal de Meleda is a rare autosomal recessive palmoplantar keratoderma (PPK), characterized by a diffuse hyperkeratosis with underlying erythroderma, nail dystrophy, malodorous hyperhidrosis and brachydactyly. Perioral erythema can be part of the phenotype [1]. The skin lesions can become infected or lead to pseudo-ainhum and joint contractures with considerable functional impairment as a consequence [2].

A related or identical PPK has been described as "Gamborg Nielsen keratoderma" [3]. Presently it appears more likely that this disorder is identical or allelic, sharing the common denominators of hyperkeratosis, brachydactyly and, rarely, mutilating pseudo-ainhum of the fingers and toes [4]. The differences between the disorders are more gradual than absolute, suggesting that they may be allelic.

Fisher et al. recently demonstrated that Mal de Meleda is associated with mutations in the ARS gene encoding the SLURP-1 (for secreted Ly6/uPAR related protein-1) protein, a member of the Ly-6/uPAR protein family and homologous to snake venom and frog neurotoxins [5]. It is speculated that as a secreted protein it may participate in signaling events using Notch-like molecules in the skin. Its receptor has not yet been identified.

Here we report on a patient of Dutch descent suffering from a form of Mal de Meleda not associated with mutations in ARS and related genes. We speculate that a mutation in the gene encoding the ARS receptor may cause the disorder in this patient.

Case report

History

The patient, a 7-year-old girl of Dutch descent, first presented to our department at age six for complaints of thickening of the skin of the palms and soles complicated by excessive, occasionally malodorous, sweating. The former complaint had been present since age three months, the latter had first appeared at one year of age. She also had thin, brittle nails. Other abnormalities had not been noted. The parents were of Dutch descent and denied consanguinity. A younger sister was not affected and the family history was wholly unremarkable otherwise. The keratoderma had been treated with topical keratolytics (mainly salicylic acid) resulting in amelioration of the keratoderma, leaving redness and scaling of the skin in its place. The hyperhidrosis was not affected by this treatment.

Physical examination

Upon physical examination we noted transgredient erythema and hyperkeratosis of the palms and soles with slight scaling, more pronounced on the palmar surface of the fingers. The hyperkeratosis had a yellowish tinge (Figs. 1 and 2) that was most apparent on the feet. Hyperhidrosis was evident on the hands. No odour was noted at the time. The appearance of the hands suggested brachydactyly, the fingers were tapered towards the tips. A circular constriction was seen encircling the basal phalanx of the right middle finger. The nails of the fingers and toes were thin and showed longitudinal ridging. Hair, teeth and nails were normal and further physical examination did not reveal other abnormalities.

Additional investigations

Informed consent of the patient's parents was obtained. A skin biopsy of the right palm was taken and examined by light and electron microscopy.

DNA was isolated from peripheral blood leucocytes using methods described elsewhere. The ARS, E48 and GML genes on chromosome 8q24.3 were amplified by genomic PCR using primers and PCR conditions as described in [5]. Prior to the sequencing reactions the PCR products were purified using the shrimp alkaline phosphatase/exonuclease presequencing kit (USB Science). Sequencing reactions were performed using the BigDyeDeoxy Terminator kit (Applied Biosystems) and were analyzed on an ABI3700 capillary sequencer (Applied Biosystems). Sequence fragments were assembled and analysed for mutations using the Phred-Phrap-Consed contig assembly software package [6-8].

Results

Skin biopsy - light microscopy: a pronounced hyperkeratosis and some acanthosis were present. The granular layer showed some hypergranularity. Some very small lipid vacuoles were seen in the stratum corneum.

Skin biopsy - electron microscopy: the granula in the granular layer were rounded and showed clear variation in size. Tonofilaments and desmosomes were normal. The basement membrane was intact. Again, hyperkeratosis and acanthosis were evident.

Mutation analysis: analysis of all coding exons and intron-exon junctions of the ARS, E48 and GML genes failed to demonstrate deviations from wild-type sequences as published by the human genome project (data available on request).

Diagnosis

Based on the history of hyperhidrosis and the transgredient hyperkeratosis, brachydactyly with tapered fingers, nail dystrophy and beginning pseudo-ainhum we made a diagnosis of Mal de Meleda. The ultrastructural findings were considered to be consistent with the diagnosis.

Treatment

The hyperhidrosis was treated using aluminium chloride 20% solution for the feet and aluminium hydroxychloride 20% in cetomacrogolis cream for the hands. This treatment led to a satisfactory reduction of the hyperhidrosis and, most importantly, of the odour. The hyperkeratosis was treated as before.

Discussion

Mal de Meleda is a disabling palmoplantar hyperkeratosis that is accompanied by malodorous hyperhidrosis, brachydactyly and sometimes auto-amputation of digits as distinguishing symptoms. Inheritance is autosomal recessive. Fisher et al. have recently demonstrated in 19 families of Maroccan and Croatian descent that the disorder is associated with mutations in the gene encoding the Ly6/uPAR family member SLURP-1, a snake venom-like secreted protein with an unknown receptor [5]. All mutations found are either nonsense or frameshift-inducing mutations, indicating that absence of SLURP-1 causes the disease phenotype. Since the disease appears to be caused by simple absence of the protein there is little room for genetically determined phenotypic variation for instance by reduction of SLURP-1 activity. Related or allelic disorders must be caused by mutations either in the ARS gene itself or in genes that interact with it.

Here we report on a young female patient of Dutch descent suffering from a hyperhidrotic transgredient palmoplantar keratoderma that we diagnosed as Mal de Meleda. Erythema was more pronounced in our patient than keratoderma per se, posing initial diagnostic difficulties. How-ever, at our patient's age, the pronounced yellow color of the keratoderma that is seen at a later age may be lacking. Moreover, treatment of the hyperkeratosis either by local means or with acitretin reveals a pronounced erythema [9]. An atypical presentation of Vörner's disease was entertained as a diagnostic possibility but deemed unlikely after reviewing the light and electron microscopic findings. We consider Gamborg Nielsen PPK to be identical or allelic to Mal de Meleda, differing only in the extent of the hyperkeratosis. Pseudo-ainhum is also seen in Vohwinkel's and Olmsted syndromes but the nature of the hyperkeratosis in these disorders differentiates them from Mal de Meleda. The modest dorsal transgression of the hyperkeratosis, the lack of ichthyosiform skin changes and the absence of perioral erythema raised initial doubts about the diagnosis. However, it appears that the latter two symptoms are rather variable, not always being present in patients (for instance [10-12]). The relatively minor dorsal transgression can be age-related. In conclusion, the hyperhidrosis, nail dystrophy, tapered fingers and brachydactyly with pseudo-ainhum of our patient are best explained by a diagnosis of Mal de Meleda. Also, the results of light and electron microscopic examination were consistent with this diagnosis. In particular, the size variation of the keratohyaline granula and lack of tonofilament aggregation parallel previously reported findings [13]. Kastl et al. report finding no size variation of keratohyaline granules in Mal de Meleda but did find it in Gamborg Nielsen PPK [3]. These conflicting data may reflect a subjective interpretation of size variation but it is more likely that they show the ultrastructural basis for the broad clinical presentation of Mal de Meleda. More studies are needed to establish the exact extent of granule size variation in Mal de Meleda. It would be of interest to search for correlations between this feature and clinical abnormalities.

The failure to find mutations in ARS may indicate that there exists genetic heterogeneity between patients suffering from Mal de Meleda. Alternatively, mosaicism may explain the failure to find mutations. However, the distribution of the skin lesions in our patient does not resemble that seen in mosaic skin disorders, making this possibility unlikely. We propose that genetic heterogeneity is a likely explanation for our findings. SLURP-1 is a protein that resembles frog and snake venoms and has the characteristics of a secreted protein. It probably serves as a ligand to an as yet unknown receptor. Similar to the situation with X-linked hypohidrotic ectodermal dysplasia and its autosomal dominant counterpart, the former being caused by mutations in the EDA gene and the latter in its receptor EDAR [14], the mutation in our patient may be in the SLURP-1 receptor.

CONCLUSION

In conclusion, we report on a patient suffering from Mal de Meleda not associated with mutations in the ARS gene on chromosome 8.

Acknowledgements

M.A.M. van Steensel is supported by grants from the Dutch Society for scientific research (NWO) grant number 920-03-085 and Rebirth SA, Luxembourg. M. van Geel is supported by a grant from Rebirth SA, Luxembourg. The authors would like to thank the anonymous reviewers for their excellent contributions.

Article accepted on 15/10/01

REFERENCES

1. Ayman T, Yerebakan O, Yilmaz E. Mal de Meleda: a review of Turkish reports. J Dermatol 2000; 27: 664-8.

2. Bergman R, Bitterman-Deutsch O, Fartasch M, Gershoni-Baruch R, Friedman-Birnbaum R. Mal de Meleda keratoderma with pseudo-ainhum. Br J Dermatol 1993; 128: 207-12.

3. Kastl I, Anton-Lamprecht I, Gamborg Nielsen P. Hereditary palmoplantar keratosis of the Gamborg Nielsen type. Clinical and ultrastructural characteristics of a new type of autosomal recessive palmoplantar keratosis. Arch Dermatol Res 1990; 282: 363-70.

4. Steijlen PM, Lucker G. Palmoplantar keratoses. In: Harper J, Oranje AP, Prose N, ed. Textbook of Pediatric Dermatology. Vol. 2. Blackwell Science, Oxford, 2000: 1122-42.

5. Fischer J, Bouadjar B, Heilig R, Huber M, Lefevre C, Jobard F, Macari F, Bakija-Konsuo A, Ait-Belkacem F, Weissenbach J, Lathrop M, Hohl D, Prud'homme JF. Mutations in the gene encoding SLURP-1 in Mal de Meleda. Hum Mol Genet 2001; 10: 875-80.

6. Ewing B, Green P. Base-calling of automated sequencer traces using phred. II. Error probabilities. Genome Res 1998; 8: 186-94.

7. Ewing B, Hillier L, Wendl MC,Green P. Base-calling of automated sequencer traces using phred. I. Accuracy assessment. Genome Res 1998; 8: 175-85.

8. Gordon D, Abajian C, Green P. Consed: a graphical tool for sequence finishing. Genome Res 1998; 8: 195-202.

9. Happle R, van de Kerkhof PC, Traupe H. Retinoids in disorders of keratinization: their use in adults. Dermatologica 1987; 175: 107-24.

10. Jee SH, Lee YY, Wu YC, Lu YC,Pan CC. Report of a family with Mal de Meleda in Taiwan: a clinical, histopathological and immunological study. Dermatologica 1985; 171: 30-7.

11. Lestringant GG, Frossard PM, Adeghate E, Qayed KI. Mal de Meleda: a report of four cases from the United Arab Emirates. Pediatr Dermatol 1997; 14: 186-91.

12. Reed ML, Stanley J, Stengel F, Shupack JL,Benjamin DM. Mal de Meleda treated with 13-cis retinoic acid. Arch Dermatol 1979; 115: 605-8.

13. Sybert VP, Dale BA, Holbrook KA. Palmar-plantar keratoderma. A clinical, ultrastructural, and biochemical study. J Am Acad Dermatol 1988; 18: 75-86.

14. Monreal AW, Ferguson BM, Headon DJ, Street SL, Overbeek PA, Zonana J. Mutations in the human homologue of mouse dl cause autosomal recessive and dominant hypohidrotic ectodermal dysplasia. Nat Genet 1999; 22: 366-9.