Lipoid proteinosis (LP) is characterized by deposition of hyaline-like material in various tissues resulting in a hoarse voice from early infancy, vesicles and hemorrhagic crusts in the mouth and on the face and extremities, verrucous and keratotic cutaneous lesions on extensor surfaces (especially the elbows), and moniliform blepharosis (multiple beaded papules along the eyelid margins and inner canthus). Extracutaneous manifestations may include epilepsy, neuropsychiatric disorders, spontaneous CNS hemorrhage, and asymptomatic multiple yellowish nodules throughout the gastrointestinal tract. Generally, the disease course is chronic and fluctuating. Males and females are affected equally. Affected individuals have a normal life span unless they experience laryngeal obstruction.

Malignant atrophic papulosis (MAP) is a rare, chronic, thrombo-obliterative vasculopathy characterized by papular skin lesions with central porcelain-white atrophy and a surrounding teleangiectatic rim. Systemic lesions may affect the gastrointestinal tract and the central nervous system (CNS) and are potentially lethal.

Keratosis pilaris atrophicans (KPA) represents a group of rare genodermatoses characterized by perifollicular keratosis and inflammation that progresses to atrophy and scarring of the facial skin. Keratosis pilaris of extensor surfaces of limbs is a common associated finding. Affected individuals may present with features that overlap between 3 subtypes, keratosis pilaris atrophicans faciei (KPAF), keratosis follicularis spinulosa decalvans (KFSD), and atrophoderma vermiculata (AVA; see 209700) (summary by Klar et al., 2015).

Xeroderma pigmentosum (XP) is characterized by: Acute sun sensitivity (severe sunburn with blistering, persistent erythema on minimal sun exposure) with marked freckle-like pigmentation of the face before age two years; Sunlight-induced ocular involvement (photophobia, severe keratitis, atrophy of the skin of the lids, ocular surface neoplasms); Greatly increased risk of sunlight-induced cutaneous neoplasms (basal cell carcinoma, squamous cell carcinoma, melanoma) within the first decade of life. Approximately 25% of affected individuals have neurologic manifestations (acquired microcephaly, diminished or absent deep tendon stretch reflexes, progressive sensorineural hearing loss, progressive cognitive impairment, and ataxia). The most common causes of death are skin cancer, neurologic degeneration, and internal cancer. The median age at death in persons with XP with neurodegeneration (29 years) was found to be younger than that in persons with XP without neurodegeneration (37 years).

Generalized basaloid follicular hamartoma syndrome is a rare, genetic skin disease characterized by multiple milium-like, comedone-like lesions and skin-colored to hyperpigmented, 1 to 2 mm-sized papules, associated with hypotrichosis and palmar/plantar pits. Lesions are usually first noticed on cheeks or neck and gradually increase in size and number to involve the scalp, face, ears, shoulders, chest, axillas, and upper arms. In severe cases, lower back, lower arms, and back of the legs can be involved. Mild hypohidrosis has also been reported.

Hereditary palmoplantar keratoderma, Gamborg-Nielsen type is characterised by the presence of diffuse palmoplantar keratoderma without associated symptoms. The syndrome has been described in multiple families from the northernmost county of Sweden (Norrbotten). The palmoplantar keratoderma found in the Gamborg-Nielsen type disease is milder than that found in Mal de Meleda but more severe than that found in Thost-Unna palmoplantar keratoderma (see these terms). Transmission is autosomal recessive.

A keratosis of the hands and feet characterized by persistent, asymptomatic, yellowish to white papules and plaques associated with fine-textured scalp hair and an atopic diathesis.

Dowling-Degos disease-4 (DDD4) is an autosomal dominant genodermatosis characterized by progressive and disfiguring reticulate hyperpigmentation. Age of onset varies between the second and sixth decade of life (summary by Basmanav et al., 2014). For a discussion of genetic heterogeneity of reticulate pigment disorders, see 179850.

Porokeratosis is a rare skin disorder characterized by one or more annular plaques with a surrounding raised horny border that spreads centrifugally. Variants of porokeratosis have been described that differ in morphologic shape, distribution, and clinical course (Schamroth et al., 1997). However, as noted by Sybert (2010), the existence of several families with expression of more than one variant of porokeratosis among members, and individuals expressing more than one variant, suggest that the distinctions among these variants may be artificial. Disseminated superficial actinic porokeratosis (DSAP) is the most common subtype of porokeratosis. It is characterized by multiple small, annular, anhidrotic, keratotic lesions that are located predominantly on sun-exposed areas of the skin, such as the face, neck, and distal limbs. The lesions typically begin to develop in adolescence and reach near-complete penetrance by the third or fourth decade of life (summary by Wu et al., 2004 and Zhang et al., 2012). For a discussion of genetic heterogeneity of porokeratosis, see 175800.

Any neonatal inflammatory skin and bowel disease in which the cause of the disease is a mutation in the EGFR gene.

A rare genetic metabolic liver disease with characteristics of progressive neurodegeneration, cutaneous abnormalities including varying degrees of ichthyosis or seborrheic dermatitis, and systemic iron overload. Patients manifest with infantile-onset seizures, encephalopathy, abnormal eye movements, axial hypotonia with peripheral hypertonia, brisk reflexes, cortical blindness and deafness, myoclonus and hepato/splenomegaly, as well as oral manifestations including microdontia, widely spaced and pointed teeth with delayed eruption and gingival overgrowth.

The basal cell nevus syndrome (BCNS), also known as Gorlin syndrome, is characterized by numerous basal cell cancers and epidermal cysts of the skin, calcified dural folds, keratocysts of the jaws, palmar and plantar pits, ovarian fibromas, medulloblastomas, lymphomesenteric cysts, fetal rhabdomyomas, and various stigmata of maldevelopment (e.g., rib and vertebral abnormalities, cleft lip or cleft palate, and cortical defects of bones) (summary by Koch et al., 2002). For a discussion of genetic heterogeneity of BCNS, see BCNS1 (109400).