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reticulate acropigmentation of kitamura ( rak ) and dowling - degos disease ( ddd ) are part of a spectrum of rare autosomal dominant genodermatosis , characterized by progressive , symmetric and asymptomatic reticulated pigmented macules affecting the dorsa of the hands , in the former , and the flexures , in the latter .
hyperpigmented lesions in rak may also involve the flexor aspects of the wrists , neck , eyelids and periorbital areas .
other features include palmoplantar pits , breaks in the epidermal ridge pattern and occasionally , plantar keratoderma and alopecia .
rak 's onset is usually in childhood unlike ddd , where the reticulate pigmentation has a late onset , in early adult life .
in addition , ddd also present comedo - like lesions and pitted acneiform scars in the face , without palmoplantar pitting .
it is very often associated with epidermoid cysts , keratoacanthoma , squamous cells carcinoma , abscess , suppurative hidrosadenitis , seborrheic keratosis and pilonidalis cysts .
the histopathology of the hyperpigmented lesions is similar and characteristic in rak and ddd , with the presence of digitated and filiform elongated rete ridges , with clumps of heavy melanin pigmentation at their tips , thinning of the epidermis and pseudo - cysts .
this resembles the appearance of a solar lentigo , but with epidermal atrophy , melanin incontinence and perivascular lymphocytic infiltrate . accordingly to the similarity in clinical and histological features , many authors consider rak and ddd different phenotypes of a single disorder . in literature
the authors found only few cases of overlap rak - ddd ( about a dozen ) , including family cases described until four generations .
an otherwise healthy 45-year - old female presented since early childhood , with a progressive and asymptomatic reticulated acropigmentation with brown pigmented macules on the dorsa of the hands , forearms and feet ( figures 1 , 2 ) .
hyperpigmented macules , ephelide - like , on both axillae , buttocks and perioral area , also appeared in adulthood ( figure 3 ) .
the physical examination revealed as well palmar pits ( figure 4 ) but no facial pitted scars , breaks in dermatoglyphics , comedo - like papules or alterations in mucous membranes , hair , teeth and nails . 

hyperpigmented macules on the dorse of the feet . 
 figure 3hyperpigmented , ephelide - like macules around the mouth . 
 
the patient reported similar lesions ( mainly the reticulated acropigmentation ) on two relatives ( mother and aunt ) apparently in an autosomal dominant pattern .
the skin biopsy of a pigmented macule of the back of the hand revealed elongated rete ridges , with increased pigmentation of the basal layer and an increment in the number of melanocytes , characteristic of rak ( figure 5 ) . 

histopathology of an hyperpigmented lesion of the dorso of the hand . based on the history , clinical and pathologic findings
, the authors believe that this case is one more example of the rare event of overlap rak - ddd , among the few non - asian cases described in literature .
rebora and crovato first suggested in 1983 that the two entities , rak and ddd were different phenotypic expressions of the same genodermatosis . in similarity to the other rak - ddd overlap cases described in the literature , our patient had typical characteristics of both variants .
concerning rak , it was possible to perceive the reticulated hyperpigmentation with acral distribution and palmar pits and ; in addition , the hyperpigmented lesions on the flexures were typical of ddd .
the true knowledge of the relationship between rak and ddd will be possibly achieved , through the clarification of the genetic background of both diseases .
reticulate acropigmentation of kitamura ( rak ) and dowling - degos disease ( ddd ) are rare genodermatosis inherited as an autosomal dominant trait with variable penetrance . 
 they are part of a spectrum of diseases with hyperpigmented macules coalescing in a reticular pattern , facial and palmoplantar pits , breaks in dermatoglyphics , comedo - like lesions and epidermoid cysts , and a unique histological picture of hyperpigmented digitate epidermal downgrowths . 
 the authors describe the case of a 45-year - old female with reticulate acropigmentation of the dorsa of the hands and feet , hyperpigmented macules on the axilla and around the mouth , and palmar pitting . 
 clinical and histological findings , together with a relevant family history , allowed the authors to consider this case an example of the rare event of an overlap rak - ddd .