nagashima - type palmoplantar keratosis ( ppk ) is characterized by transgressive and non - progressive keratosis with an autosomal recessive trait . nagashima - type ppk was first described in japan in 1977 and then followed by more than 20 cases in the japanese literature . since nagashima - type ppk is generally seen in isolated cases , it has been suggested that the mode of inheritance is autosomal recessive . however , a case of nagashima - type ppk in 2 siblings   as well as a familial case of this type of ppk , occurring in father and son , was also reported . the latter report raises the question of whether nagashima - type ppk is mediated only through the autosomal recessive trait . here a 9-year - old girl and her 6-year - old sister presented with bilateral reddish , palmoplantar , hyperkeratotic lesions with erythematous borders ( fig . 1a d ) . the lesions transgressed to the extensor surface of the fingers and toes . they had been treated with betamethasone valerate 0.1% and gentamicin sulfate ointment , which resulted in no improvement . their conditions were associated with hyperhidrosis on the palms and soles with distinct odor and maceration . only the elder sister exhibited the clinical manifestations on her elbows and knees ( fig . 1e , f ) , and both patients showed no involvement of the hair , nails , or teeth . the patients were isolated cases in their family , and their parents were a non - consanguineous couple . the parents declined a skin biopsy . the clinical manifestation , including transgressive ppk to the extensor surfaces , indicated a diagnosis of nagashima - type ppk or mal de meleda ( mdm ) . mdm is an autosomal recessive ppk with a progressive clinical course throughout the patients lives . since the patients in this report were still young , it will require more time to determine whether their clinical status is progressive or not . in addition , mdm is usually accompanied by perioral erythema , brachydactyly , and nail abnormalities . hyperkeratosis extends to the dorsal surfaces of the hands and feet , and the progressive lesions , including constricting bands surrounding the digits , can result in spontaneous amputation . while the mutation in slurp1 is known to be responsible for mdm , genetic analysis has not yet identified the responsible gene in nagashima - type ppk . nagashima - type ppk was proposed as a novel entity of ppk , and the manifestations are much less severe and non - progressive after puberty . although we could not exclude a diagnosis of mdm because the parents declined genetic analysis , the clinical manifestations seen in our patients were consistent with nagashima - type ppk . herein , we showed a second case of possible nagashima - type ppk in 2 siblings in the english literature . our patients had non - affected parents , suggesting that the mode of inheritance was autosomal recessive , though both recessive and dominant inheritance of nagashima - type ppk may occur . at present , reports on ppk in the english literature are limited , and thus the clinical features of nagashima - type ppk may not be well appreciated in western countries . more reports and concise clinical observations with genetic studies are required to establish the new entity of ppk . we believe the accumulation of information on the disease may reveal its underlying pathomechanism in the near future .
nagashima - type palmoplantar keratosis ( ppk ) is an autosomal recessive , transgressive and non - progressive form of ppk . 
 it was once described as a mild form of mal de meleda , but it is now proposed as a novel entity of ppk . since its pathogenesis remains unclear , it is important to clarify the mode of inheritance . here , 
 we present a case of possible nagashima - type ppk in 2 siblings . 
 the siblings had non - affected parents , suggesting that the mode of inheritance was autosomal recessive . at present , reports on ppk in the english literature are limited , and thus the clinical features of nagashima - type ppk may not be well appreciated in western countries . 
 more reports and concise clinical observations with genetic studies are required to establish this new entity of ppk .