Atrophoderma vermiculata, a form of keratosis pilaris atrophicans, typically presents in childhood with erythema and follicular keratotic papules that slowly progress to characteristic atrophy, which has been described as worm-eaten, reticular, or honeycomb, and occurs on the cheeks, preauricular area, and forehead. More rarely, the atrophy may extend to the upper lip, helices, ear lobes, and, in some cases, the limbs. The degree of inflammation, the presence of milia, and the extent of follicular plugs are variable (summary by Luria and Conologue, 2009).

Bart-Pumphrey syndrome (BAPS) is an autosomal dominant disorder characterized by sensorineural hearing loss, palmoplantar keratoderma, knuckle pads, and leukonychia, which shows considerable phenotypic variability (summary by Richard et al., 2004).

Trichorhinophalangeal syndrome (TRPS) comprises TRPS I (caused by a heterozygous pathogenic variant in TRPS1) and TRPS II (caused by contiguous gene deletion of TRPS1, RAD21, and EXT1). Both types of TRPS are characterized by distinctive facial features; ectodermal features (fine, sparse, depigmented, and slow growing hair; dystrophic nails; and small breasts); and skeletal findings (short stature; short feet; brachydactyly with ulnar or radial deviation of the fingers; and early, marked hip dysplasia). TRPS II is characterized by multiple osteochondromas (typically first observed clinically on the scapulae and around the elbows and knees between ages 1 month and 6 years) and an increased risk of mild-to-moderate intellectual disability.

Any inherited isolated nail anomaly in which the cause of the disease is a mutation in the PLCD1 gene.

Autosomal recessive congenital ichthyosis (ARCI) encompasses several forms of nonsyndromic ichthyosis. Although most neonates with ARCI are collodion babies, the clinical presentation and severity of ARCI may vary significantly, ranging from harlequin ichthyosis, the most severe and often fatal form, to lamellar ichthyosis (LI) and (nonbullous) congenital ichthyosiform erythroderma (CIE). These phenotypes are now recognized to fall on a continuum; however, the phenotypic descriptions are clinically useful for clarification of prognosis and management. Infants with harlequin ichthyosis are usually born prematurely and are encased in thick, hard, armor-like plates of cornified skin that severely restrict movement. Life-threatening complications in the immediate postnatal period include respiratory distress, feeding problems, and systemic infection. Collodion babies are born with a taut, shiny, translucent or opaque membrane that encases the entire body and lasts for days to weeks. LI and CIE are seemingly distinct phenotypes: classic, severe LI with dark brown, plate-like scale with no erythroderma and CIE with finer whiter scale and underlying generalized redness of the skin. Affected individuals with severe involvement can have ectropion, eclabium, scarring alopecia involving the scalp and eyebrows, and palmar and plantar keratoderma. Besides these major forms of nonsyndromic ichthyosis, a few rare subtypes have been recognized, such as bathing suit ichthyosis, self-improving collodion ichthyosis, or ichthyosis-prematurity syndrome.

Hypotrichosis and recurrent skin vesicles (HYPTSV) is characterized by sparse to absent scalp hair, eyebrows, eyelashes, and body hair, as well as recurrent vesicles of scalp and skin. Some patients also exhibit trauma-induced blistering, and anomalies of dental enamel and of nails may be observed (Ayub et al., 2009; Onoufriadis et al., 2020).

Keratoderma with woolly hair is a group of related conditions that affect the skin and hair and in many cases increase the risk of potentially life-threatening heart problems. People with these conditions have hair that is unusually coarse, dry, fine, and tightly curled. In some cases, the hair is also sparse. The woolly hair texture typically affects only scalp hair and is present from birth. Starting early in life, affected individuals also develop palmoplantar keratoderma, a condition that causes skin on the palms of the hands and the soles of the feet to become thick, scaly, and calloused.\n\nCardiomyopathy, which is a disease of the heart muscle, is a life-threatening health problem that can develop in people with keratoderma with woolly hair. Unlike the other features of this condition, signs and symptoms of cardiomyopathy may not appear until adolescence or later. Complications of cardiomyopathy can include an abnormal heartbeat (arrhythmia), heart failure, and sudden death.\n\nKeratoderma with woolly hair comprises several related conditions with overlapping signs and symptoms. Researchers have recently proposed classifying keratoderma with woolly hair into four types, based on the underlying genetic cause. Type I, also known as Naxos disease, is characterized by palmoplantar keratoderma, woolly hair, and a form of cardiomyopathy called arrhythmogenic right ventricular cardiomyopathy (ARVC). Type II, also known as Carvajal syndrome, has hair and skin abnormalities similar to type I but features a different form of cardiomyopathy, called dilated left ventricular cardiomyopathy. Type III also has signs and symptoms similar to those of type I, including ARVC, although the hair and skin abnormalities are often milder. Type IV is characterized by palmoplantar keratoderma and woolly and sparse hair, as well as abnormal fingernails and toenails. Type IV does not appear to cause cardiomyopathy.

Palmoplantar keratoderma and woolly hair (PPKWH) is an autosomal recessive disorder characterized by the presence of these cardinal features and the absence of cardiomyopathy symptoms or findings on echocardiography and electrocardiogram. Palmoplantar keratoderma is of the striate type; hair is generally sparse; and leukonychia is present (Ramot et al., 2014).

Heimler syndrome, which represents the mildest end of the peroxisomal biogenesis disorder spectrum (see PBD1A, 214100), is a rare autosomal recessive disorder characterized by sensorineural hearing loss, enamel hypoplasia of the secondary dentition, and nail abnormalities (Ratbi et al., 2015). For a discussion of genetic heterogeneity of Heimler syndrome, see HMLR1 (234580).

A rare genetic skin disease characterized by generalized skin peeling, leukonychia, acral punctate keratoses coalescing into focal keratoderma on the weight-bearing areas, angular cheilitis and knuckle pads with multiple hyperkeratotic micropapules. The skin appears dry and scaly with superficial exfoliation and underlying erythema. Histopathologic examination of affected skin areas shows hyperkeratosis, acanthosis and intraepidermal clefting with irregular acantholysis. Additional systemic abnormalities are absent.

Palmoplantar keratoderma and congenital alopecia-1 (PPKCA1) is a rare autosomal dominant disorder characterized by severe hyperkeratosis and congenital alopecia. Nail changes occur in some patients (summary by Castori et al., 2010). Also see PPKCA2 (212360), an autosomal recessive disorder characterized by congenital alopecia and progressive hyperkeratosis resulting in sclerodactyly, severe contractures and tapering of the digits, and pseudoainhum formation.

Erythrokeratodermia variabilis et progressiva is a rare skin disease. Patients with EKVP3 have normal skin at birth but develop hyperpigmentation and scaling at sites of friction in childhood, with progression to near-confluent corrugated hyperkeratosis, palmoplantar keratoderma, and transient figurate erythema (summary by Boyden et al., 2015). For a discussion of genetic heterogeneity of EKVP, see EKVP1 (133200).

Heimler syndrome-1 (HMLR1), which represents the mildest end of the peroxisomal biogenesis disorder spectrum (see PBD1A, 214100), is a rare autosomal recessive disorder characterized by sensorineural hearing loss, enamel hyoplasia of the secondary dentition, and nail abnormalities (Ratbi et al., 2015). Genetic Heterogeneity of Heimler Syndrome Another form of Heimler syndrome (HMLR2; 616617) is caused by mutation in the PEX6 gene (601498) on chromosome 6p21.

Ichthyosis with erythrokeratoderma (IEKD) is an autosomal dominant disorder of cornification characterized by abnormal desquamation in addition to erythematous hyperkeratotic plaques or patches. Lesions are present at birth or appear soon after (Gong et al., 2023; Takeichi et al., 2023).