A i.e. Dowling-Degos disease Dowling-Degos disease presents as asymptomatic post-pubeal, symmetrical, progressive, reticular pigmentation involving flexural-areas (flexor folds) with scattered comedo like lesions (dark dot follicles) and pitted aceniform scars near angles of mouthQ. Reticular acropimentation of kitamura presents with reticular freckle like pigmentation on dorsal hands, palmar pitsQ and breakage of epidermal ridge pattern. Cockayne's syndrome, Bloom's syndrome and Rothmund-Thomson syndrome are genodermatoses with defective DNA repairing, presenting as photo sensitivity. Dowling-Degos disease Dowling-Degos disease (reticular pigmented anomaly of flexures) is a rare autosomal dominant genodermatoses usually presenting post pubeally with multiple small, round pigmented macules that resemble freckles. Pigmentation is symmetrical and progressive; and the lesions become progressively more numerous and reticulate with time. It characteristically involves flexurals areasQ e.g: axillae, groins (mc sites), intergluteal/ infra-mammary folds, neck, scalp, trunk, arms and genitals. Except pigmentation, it is otherwise asymptomatic (rarely pruritic). Scattered comedo like lesions (dark dot follicles) pitted acneiform scars near angels of mouthQ and hidradenitis suppurativa are other features. Histology is diagnostic, with a distinctive form of acanthosis, characterized by an irregular elongation of rete ridges, with a concentration of melanin at the tips (filiform down growths in epidermis with hyperpigmentation of deepest areas); the melanocyte count being normal. It involves follicular infundibulum with follicular plugging in some cases. Reticulate acropigmentation of Kitamura Reticulate acropigmentation of kitamura is characterized by a reticulate network of freckle like areas of pigmentation which develop on dorsa of hands in first 2 decades, which may subsequently involve most pas of body. Palmar pits and breakages of epidermal ridge pattern are foundQ. Histologically, the pigmented macules show epidermal atrophy and increased number of melanocytes. Hereditary symmetrical dyskeratosis of extremities (reticulate acropimentation of Dohi) is AD disorder presenting in infancy or early childhood as mottled pigmentation with areas of depigmentation on dorsa of hands and feet or arms and legs. Haber's syndrome - Haber's syndrome is a familial condition characterized by persistent/permanent rosacea like eruption (i.e. facial flushing, erythema, telangiectasia, prominent follicles, comedones, small papules and tiny atrophic pitted areas) associated in some cases with static, scaly/keratotic, flat, non-indurated plaques on trunk and limbs. Bloom's syndrome Bloom's syndrome (congenital telangiectatic erythema and stunted growth) is a AR disorder characterized by photosensitive telagiestatic facial erythema during infancy or early childhood (superficially resembling lupus erythematosus), moderate and propoionate growth deficiency both in utero and postnatally, unusual facies (narrow, slender, delicate face with a narrow, prominent nose, hypoplastic malar areas, receding chin and microcephaly and dolichocephaly i.e. long and narrow head). Patients are predisposed to multiple infection (d/t immune dysfunction) and early cancers (usually interanal) lit early death (usually neurological development is normal; diabetes mellitus and testicular atrophy are common. Cockayne's syndrome Cockayne's syndrome is AR degenerative disease with cutaneous (photosensitivity, premature skin aging), ocular (pigmentary retinal degeneration with salt-peper appearance of retina, optic atropy and cataract), neurological (sensorineural deafness, progressive neurological degeneration, extensive primary demyelination, peripheral neuropathy, normal pressure hydrocephalus, microcephaly, intellectual deterioration) and somatic abnormalities (postnatal growth failure, cachectic dwarfism with dispropoionately long limbs with large hands and feet and ears). Child usually appears normal for the first year, when photosensitive butterfly facial erythema develop 1/ t mottled pigmentation, atrophic scars giving patient a prematurely senile appearance which is enhanced by marked loss of subcutaneous fat on face (wizened appearance) and sunken eyes with typical bird headed facies and prominent Mickey mouse ear. In contrast to xerodema pigmentosa, CS don't have increased incidence of skin cancer and infection and the CS patients have unusual facies, demyelination with delayed nerve conduction velocity and normal level of global NER. Rothmund Thomson Syndrome Rothmund Thomson syndrome (congenital poikiloderma), an AR disorder is characterized by poikiloderma with variegated cutaneous pigmentation, atrophy and telangiectasia beginning in infancy (but not bih). Cheeks are fist and most severly involved but face, buttock and extremities are also involved. Photosensitive erythema and facial smelling may be accompanied by blister formation. Scalp hair, eyebrows, eyelashes, pubic and axillary hair are often sparse or absent. Juvenile cataract (b/l), propoionate stunted growth with slender delicate limb, small hands, feet and finger; bird like small skull with a saddle nose, skelatel abnormalities including radial ray defect (present as thumb hypoplasia, abnormal radial head or absence of radius) and a predisposition for cancer especially osteosarcoma (30%). Intelligence is normal and life expectancy depends on development of cancer; otherwise it appears to be normal.