Reticulate Acropigmentation of Kitamura (RAK)

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OMIM®: ⁵⁷ Reticulate acropigmentation of Kitamura (RAK) is a rare pigmentary disorder that usually shows an autosomal dominant pattern of inheritance with high penetrance. Typical features include reticulate, slightly depressed, sharply demarcated brown macules without hypopigmentation, affecting the dorsa of the hands and feet in the first or second decade of life. The macules gradually darken and extend to the proximal regions of the extremities; progression of the eruptions stops in middle age. The increased pigmentation is found on the flexor aspects of the wrists, neck, patella, and olecranon. Other features include breaks in the epidermal ridges on the palms and fingers, palmoplantar pits, partial alopecia, and occasionally plantar keratoderma. Histopathologically, the brown macules show pigmentation in the tip of rete ridges with thinning of the epidermis, elongation and thinning of the rete ridges, and slight hyperkeratosis without parakeratosis. Only a few inflammatory cell infiltrates and no incontinentia pigmenti are seen in the dermis (summary by Kono et al., 2013). (615537) (Updated 08-Dec-2022)

MalaCards based summary: Reticulate Acropigmentation of Kitamura, also known as rak, is related to dowling-degos disease 1 and dowling-degos disease. An important gene associated with Reticulate Acropigmentation of Kitamura is ADAM10 (ADAM Metallopeptidase Domain 10), and among its related pathways/superpathways are Pre-NOTCH Expression and Processing and Keratinization. Affiliated tissues include skin, and related phenotypes are hyperkeratosis and Increased shRNA abundance (Z-score > 2)

UniProtKB/Swiss-Prot: ⁷³ A rare cutaneous pigmentation disorder characterized by reticulate, slightly depressed, sharply demarcated brown macules without hypopigmentation, affecting the dorsa of the hands and feet and appearing in the first or second decade of life. The macules gradually darken and extend to the proximal regions of the extremities. The manifestations tend to progress until middle age, after which progression of the eruptions stops. The pigmentary augmentation is found on the flexor aspects of the wrists, neck, patella and olecranon. Other features include breaks in the epidermal ridges on the palms and fingers, palmoplantar pits, occasionally plantar keratoderma, and partial alopecia.

Orphanet: ⁵⁸ A rare, genetic, hyperpigmentation of the skin disease characterized by childhood to adulthood-onset of reticulate, slightly depressed, sharply demarcated, brown, macular skin lesions without hypopigmentation, affecting the dorsa of the hands and feet, and, occasionally, progressing to involve limbs, neck, forehead and/or trunk. Interrupted dermatoglyphics and palmoplantar pits may be additionally observed. Histologically, hyperpigmented lesions show slightly elongated and thinned rete ridges, mild hyperkeratosis without parakeratosis and absence of incontinentia pigmenti.

Disease Ontology: ¹¹ A pigmentation disease characterized by lesions that initially arise as letiginous, hyperpigmented macules in a reticular pattern on the dorsal aspect of the hands and feet. Over time, lesions may spread proximally and may darken; palmoplantar pitting and dermatoglyphic disruption may also be present.

Wikipedia: ⁷⁵ Reticulate acropigmentation of Kitamura is a type of pigmentation disorder of the skin. It presents with... more...

Clinical features from OMIM®:

Search Clinical Trials, NIH Clinical Center for Reticulate Acropigmentation of Kitamura