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Reticulate acropigmentation of Kitamura (RAPK) was first described by Kitamura and Akamatsu in 1943.[1, 2] Most reported cases have been Japanese, but it is also reported worldwide.[3] RAPK is a sporadic or autosomal-dominant disease characterized by reticulate pigmentation mainly on the dorsa of the hands and feet, and by punctuate depressions on the palms and soles. It seems inheritable, but the aetiology remains unknown.[4] We describe the characteristic findings of handprint and dermoscopy seen in a sporadic case of RAPK, which were quite useful for correct diagnosis.

A 38-year-old Japanese woman presented with asymptomatic pigmentation mainly on her limbs. The eruptions had been present since she was 12 years of age, and had darkened with time. There was no familial history of similar eruptions.

On physical examination, asymmetrical, irregular brownish macules, 0.5–5 mm in size, were seen on the patient's face, neck, trunk, axillae, legs, arms, and dorsal hands, without any hypopigmented areas (Fig. 1a).

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Figure 1. (a) Asymmetrical reticulate hyperpigmented macules on the dorsa of the hands. (b) Using a dermoscope, the hyperpigmented macules on the dorsum of the foot were seen to form brownish reticular pigment networks. Hyperpigmented macules on other sites of the body presented similar findings. (c) Slight elongation of the rete ridges with melanization of the tips was seen (haematoxylin and eosin, original magnification × 200).

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On histological examination of a skin biopsy taken from the dorsum of the left foot, elongation of the rete ridges was seen, with melanization of the tips (Fig. 1c). Of note, there were numerous punctate depressions on the palms and soles (Fig. 2a; black arrows). The depressions were not clear macroscopically; however, they became evident when a handprint was compared with that of a control person (Fig. 2b; red arrows).

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Figure 2. (a) Punctate depressions (black arrows) on the left palm. (b) Handprints of the left palm of (left) the patient and (right) control). Numerous depressions are visible on the hand of the patient (red arrows) but not on that of the control. These depressions occurred mostly along dermatoglyphs and were distributed over the whole palm. (c) Under the dermoscope, some of the punctate depressions were seen to correspond in location to the patchy brownish spots.

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The dermoscopic findings were of fine reticular pigment networks (Fig. 1b), but no hypopigmented areas were seen. Many of the punctate depressions on the palm and soles corresponded in location to patchy pigmented spots (Fig. 2c).

Based on these findings, we made a diagnosis of RAPK.

In 1943, Kitamura et al.[1, 2] described three clinical hallmarks of RAPK: absence of hypopigmented macules, presence of various kinds of hyperpigmented macules, and presence of slight depressions in the skin surface corresponding to the pigmentation. The absence of hypopigmented macules anywhere on the body and the presence of punctate depressions on the palms and soles differentiate RAPK from other hyperpigmentation disorders such as dyschromatosis symmetrica hereditaria (DSH).[4, 5] A Japanese textbook shows the handprint of a patient with RAPK with punctate depressions,[5] and our report clarifies that a handprint is useful for visualizing the punctate depressions on the palms, especially when the handprint is compared with that of a control person.

Our report, shows for the first time, to our knowledge, the dermoscopic findings of RAPK. Hyperpigmented macules were seen, forming a fine reticular pigment network, which reflects the histopathological findings. This network is a nonspecific finding because it is also seen in Clark naevus, congenital naevus, melanoma and other conditions. By contrast, the patchy brownish-pigmented spots coinciding with the punctate depressions on the palms and soles seem to be characteristic of RAPK. The spots that became apparent upon dermoscopy were heterogeneous and lacked pigment networks or other previously established patterns. In the first reported instance of RAPK, Kitamura et al.[1, 2] described slight depressions in the skin surface corresponding to pigmentation. It may be difficult to detect the finding by macroscopic examination; however, dermoscopy makes it clear that the depressions on the palms and soles coincide with the patchy pigmented spots. Careful dermoscopic observation to detect this feature promises to be useful in differentiating RAPK from other pigmented disorders such as DSH.

References

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  2. References
  • 1
    Kitamura K, Akamatsu S. Ni San-no hifu shikisoijo. Rinsho No Hifu Hinyo 1943; 8: 2014.
  • 2
    Kitamura K, Akamatsu S, Hirokawa K. [A special form of acropigmentation: acropigmentatio reticularis] (in German). Hautarzt 1953; 4: 1526.
  • 3
    Griffiths WAD. Reticulate acropigmentation of Kitamura. Br J Dermatol 1976; 95: 43743.
  • 4
    Suzuki N, Suzuki T, Inagaki K et al. Mutation analysis of the ADAR1 gene in dyschromatosis symmetrica hereditaria and genetic differentiation from both dyschromatosis universalis hereditaria and acropigmentatio reticularis. J Invest Dermatol 2005; 124: 118692.
  • 5
    Kanemoto Y. [Acropigmentatio reticularis] (in Japanese). In: Comprehensive Handbook of Clinical Dermatology, (Tamaki K, Iizuka H, Shimizu H et al. eds). Tokyo: Nakayama Shoten, 2002; 8: 403.