Seasonal palmar keratoderma in erythropoietic protoporphyria indicates autosomal recessive inheritance.
Erythropoietic protoporphyria (EPP) is an inherited disorder that results from partial deficiency of ferrochelatase (FECH). It is characterized clinically by acute photosensitivity and, in 2% of patients, liver disease. Inheritance is usually autosomal dominant with low penetrance but is recessive in about 4% of families. A cross-sectional study of 223 patients with EPP in the United Kingdom identified six individuals with palmar keratoderma. We now show that these and three additional patients, from six families, have an inherited subtype of EPP which is characterized by seasonal palmar keratoderma, relatively low erythrocyte protoporphyrin concentrations, and recessive inheritance. No patient had evidence of liver dysfunction; four patients had neurological abnormalities. Patients were hetero- or homoallelic for nine different FECH mutations; four of which were previously unreported. Prokaryotic expression predicted that FECH activities were 2.7-25% (mean 10.6%) of normal. Neither mutation type nor FECH activity provided an explanation for the unusual phenotype. Our findings show that palmar keratoderma is a clinical indicator of recessive EPP, identify a phenotype that occurs in 38% of reported families with recessive EPP that to our knowledge is previously unreported, and suggest that patients with this phenotype may carry a lower risk of liver disease than other patients with recessive EPP.
Holme
S Alexander
SA
Department of Dermatology, School of Medicine, University Hospital of Wales, Cardiff University, Cardiff, UK.
Whatley
Sharon D
SD
Roberts
Andrew G
AG
Anstey
Alexander V
AV
Elder
George H
GH
Ead
Russell D
RD
Stewart
M Felicity
MF
Farr
Peter M
PM
Lewis
Helen M
HM
Davies
Nicholas
N
White
Marion I
MI
Ackroyd
R Simon
RS
Badminton
Michael N
MN
D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D005294:Ferrochelatase / Q000235:genetics* / Q000502:physiology; D005808:Genes, Recessive; D005838:Genotype; D006801:Humans; D007645:Keratoderma, Palmoplantar / Q000150:complications* / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010641:Phenotype; D046351:Protoporphyria, Erythropoietic / Q000150:complications* / Q000235:genetics*; D012621:Seasons
D005294:Ferrochelatase