Reticulate Acropigmentation of Kitamura
Reticulate acropigmentation of Kitamura (RAK) is a rare autosomal dominant disorder within the group of reticulate pigmentary dermatoses. At the molecular level, RAK is linked to loss-of-function mutations in the ADAM10 gene (locus 15q21.3–q22.2), which encodes a cell-membrane metalloproteinase. This enzyme plays a key role in the cleavage and activation steps of the Notch signaling pathway — the core regulatory axis that controls keratinocyte differentiation, maintains epidermal balance and governs communication between keratinocytes and melanocytes.
Reduced Notch signaling from ADAM10 mutations has two parallel effects. On one hand, it disturbs keratinization and keratinocyte turnover, causing focal thinning of the epidermis and the characteristic pits on the palms and soles. On the other, the breakdown in keratinocyte–melanocyte cross-talk drives disorganized melanosome production, which shows up clinically as slightly depressed, brown-black macules in a net-like pattern, distributed symmetrically mainly on the backs of the hands and feet and darkening gradually with age.
At Haute-Derma, we view RAK as a combined structural and pigmentary defect with atrophy. The main challenge is not just clearing pigment but dealing with the accompanying epidermal atrophy. Our approach therefore moves away from harsh thermal ablation toward fractional epithelial remodeling combined with mechanical (photoacoustic) energy, aiming both to smooth the depressed, atrophic skin and to clear the net-like pigment as cleanly as possible.
Our Approach to Managing Kitamura Syndrome (RAK)
Because RAK combines pigmentation with atrophy on the hands and feet, Haute-Derma follows standardized treatment principles:
- Treating pigment and structure together: The plan must tackle two goals at once — smoothing the atrophic epidermal depressions and breaking up the net-like bands of pigment.
- Strict control of heat on the hands and feet: The backs of the hands and feet have a very thin dermal cushion and a poorer blood supply than the face. Any laser treatment must therefore avoid heat buildup to prevent microscopic tissue necrosis or permanent post-inflammatory hyperpigmentation (PIH).
- Supporting the keratinocyte cycle: We aim to restore faulty epidermal differentiation with actives that stimulate local stem cells, helping to fill in the palmar pits.
Screening and Clinical Assessment at Haute-Derma
To map out treatment precisely, Haute-Derma follows a careful microscopic assessment:
- Dermoscopy of skin ridges and pits: Under dermoscopy, the doctor sees a tight network of spindle-shaped brown-black spots around the follicles on the hands and feet. On the palms and soles, we look for breaks in the epidermal ridges that form the pinpoint palmar/plantar pits typical of Kitamura syndrome.
- Histopathology: Biopsy of RAK shows a classic picture: elongated, thin, filiform rete ridges extending down into the dermis, with dense melanin at their tips. The epidermis at the center of the lesion is clearly thinned, but the number of melanocytes is not increased (this is not a melanocytic proliferation).
- Gene sequencing to identify the variant: A pigmentation gene panel using next-generation sequencing (NGS) detects point or frameshift mutations in ADAM10, confirming the diagnosis at the molecular level.
- Systematic differential diagnosis: Careful analysis rules out Dowling-Degos disease (which usually affects skin folds and has comedo-like lesions) and dyschromatosis symmetrica hereditaria (DSH), which has interspersed white depigmented spots and no atrophy.
Clinical Management and Aesthetic Treatment at Haute-Derma
Our overall strategy aims to resurface the atrophic depressions and even out skin color:
- Picosecond laser (755 nm / 1064 nm) with a honeycomb focus lens: Ultrashort picosecond pulses create a purely mechanical (photoacoustic) effect. High-peak-power microbeams produce tiny zones of mechanical injury within the epidermis that trigger the tissue's natural repair response to fill in the atrophic macules, while shattering melanin in the basal layer without releasing heat that could harm the hands and feet.
- Sterile RF microneedling: Gold-coated microneedles deliver radiofrequency energy precisely into the superficial dermis beneath the atrophic spots. The combined mechanical and controlled thermal effect stimulates type I and III collagen and remodels the stretched rete ridges, helping to smooth the pits on the palms and backs of the hands.
- Topical regulators of epidermal differentiation: An evening regimen with a new-generation retinoid (such as trifarotene or tazarotene) combined with bakuchiol and ceramide NP. This combination is intended to partly compensate for the weakened Notch pathway, speeding keratinocyte turnover, normalizing keratinization and reducing pigment buildup in the basal layer.
- Sun protection and intensive barrier repair: A broad-spectrum, highly water-resistant medical sunscreen plus barrier-repair ingredients such as hydrolyzed hyaluronic acid and panthenol protect the sensitive skin of the hands and feet from UV-triggered pigment activation.
