Chilblain lupus is a cutaneous form of systemic lupus erythematosus (SLE; 152700) characterized by the appearance of painful bluish-red papular or nodular lesions of the skin in acral locations (including the dorsal aspects of fingers and toes, heels, nose, cheeks, ears, and, in some cases, knees) precipitated by cold and wet exposure (summary by Lee-Kirsch et al., 2006). Genetic Heterogeneity of Chilblain Lupus See also CHBL2 (614415), caused by mutation in the SAMHD1 gene (606754) on chromosome 20q11. Mutations in the TREX1 and SAMHD1 genes also cause Aicardi-Goutieres syndrome (AGS1, 225750 and AGS5, 612952, respectively).

Sjogren-Larsson syndrome (SLS) is an autosomal recessive, early childhood-onset disorder characterized by ichthyosis, impaired intellectual development, spastic paraparesis, macular dystrophy, and leukoencephalopathy. It is caused by deficiency of fatty aldehyde dehydrogenase (summary by Lossos et al., 2006).

Johanson-Blizzard syndrome is an autosomal recessive disorder characterized by poor growth, mental retardation, and variable dysmorphic features, including aplasia or hypoplasia of the nasal alae, abnormal hair patterns or scalp defects, and oligodontia. Other features include hypothyroidism, sensorineural hearing loss, imperforate anus, and pancreatic exocrine insufficiency (summary by Al-Dosari et al., 2008).

Congenital absence/hypoplasia of fingers excluding thumb, unilateral is a rare, non-syndromic, terminal transverse limb reduction defect characterized by unilateral absence of the terminal portions of digits 2 to 5, with a mildly hypoplastic thumb and small nail remnants on the digital stumps. Metacarpal bones may be variably reduced.

The most basic description of Moebius syndrome is a congenital facial palsy with impairment of ocular abduction. The facial nerve (cranial nerve VII) and abducens nerve (CN VI) are most frequently involved, but other cranial nerves may be involved as well. Other variable features include orofacial dysmorphism and limb malformations. Mental retardation has been reported in a subset of patients. Most cases of Moebius syndrome are sporadic, but familial occurrence has been reported (Verzijl et al., 2003). The definition of and diagnostic criteria for Moebius syndrome have been controversial and problematic. The syndrome has most frequently been confused with hereditary congenital facial paresis (HCFP; see 601471), which is restricted to involvement of the facial nerve and no other abnormalities. Verzijl et al. (2003) and Verzijl et al. (2005) concluded that HCFP and Moebius syndrome are distinct disorders, and that Moebius syndrome is a complex developmental disorder of the brainstem. Moebius syndrome was defined at the Moebius Syndrome Foundation Research Conference in 2007 as congenital, nonprogressive facial weakness with limited abduction of one or both eyes. Additional features can include hearing loss and other cranial nerve dysfunction, as well as motor, orofacial, musculoskeletal, neurodevelopmental, and social problems (summary by Webb et al., 2012). Kumar (1990) provided a review of Moebius syndrome, which was critiqued by Lipson et al. (1990). Briegel (2006) provided a review of Moebius sequence with special emphasis on neuropsychiatric findings.

Hereditary bullous dystrophy of the macular type (HBDM) is a rare X-linked recessive disorder characterized by the formation of bullae without evident trauma, hyper- and hypopigmentation, absence of hair at birth, and, in some cases, microcephaly, mildly impaired intellectual development, short conic fingers, and aberrations of nails (summary by Wijker et al., 1995).

A rare primary bone dysplasia disorder with characteristics of severe short stature, coarse facies, thoracolumbar kyphoscoliosis and enlarged joints with contractures. Psychomotor delay and intellectual disability may also be associated. Radiographic features include flat vertebral bodies, lacy ossification of the metaphyses of long bones and iliac crests, and marked sclerosis of the skull base.

Congenital hypotrichosis with juvenile macular dystrophy (HJMD) is an autosomal recessive disorder characterized by hair loss followed by progressive macular degeneration and early blindness. Scalp hair is lost during the first months of life, with onset of retinal degeneration and vision loss a few years to 2 decades later (summary by Sprecher et al., 2001 and Indelman et al., 2002).

A rare disorder with manifestation of hypo or oligodontia and acanthosis nigricans. It has been described in four generations of one family. Onset generally occurs during adolescence. Some patients are born with multiple teeth. Hair anomalies (sparse body and scalp hair) also reported. Inheritance is autosomal dominant.

A very rare hereditary skin disease with manifestation of irregularly distributed epidermal hyperkeratosis of the palms and soles. Reported in 35 families worldwide to date. The lesions usually start to develop in early adolescence but can also present later in life. Mutations in the AAGAB gene (15q22.33-q23) have recently been identified as one of the causes. Mutations in the COL14A1 gene (8q23) have also been identified as causal in some cases in Asia that seem to have a similar phenotype

Autosomal recessive congenital ichthyosis (ARCI) is a heterogeneous group of disorders of keratinization characterized primarily by abnormal skin scaling over the whole body. These disorders are limited to skin, with approximately two-thirds of patients presenting severe symptoms. The main skin phenotypes are lamellar ichthyosis (LI) and nonbullous congenital ichthyosiform erythroderma (NCIE), although phenotypic overlap within the same patient or among patients from the same family can occur (summary by Fischer, 2009). Neither histopathologic findings nor ultrastructural features clearly distinguish between NCIE and LI. In addition, mutations in several genes have been shown to cause both lamellar and nonbullous ichthyosiform erythrodermal phenotypes (Akiyama et al., 2003). At the First Ichthyosis Consensus Conference in Soreze in 2009, the term 'autosomal recessive congenital ichthyosis' (ARCI) was designated to encompass LI, NCIE, and harlequin ichthyosis (ARCI4B; 242500) (Oji et al., 2010). NCIE is characterized by prominent erythroderma and fine white, superficial, semiadherent scales. Most patients present with collodion membrane at birth and have palmoplantar keratoderma, often with painful fissures, digital contractures, and loss of pulp volume. In half of the cases, a nail dystrophy including ridging, subungual hyperkeratosis, or hypoplasia has been described. Ectropion, eclabium, scalp involvement, and loss of eyebrows and lashes seem to be more frequent in NCIE than in lamellar ichthyosis (summary by Fischer et al., 2000). In LI, the scales are large, adherent, dark, and pigmented with no skin erythema. Overlapping phenotypes may depend on the age of the patient and the region of the body. The terminal differentiation of the epidermis is perturbed in both forms, leading to reduced barrier function and defects of lipid composition in the stratum corneum (summary by Lefevre et al., 2006). In later life, the skin in ARCI may have scales that cover the entire body surface, including the flexural folds, and the scales are highly variable in size and color. Erythema may be very mild and almost invisible. Some affected persons exhibit scarring alopecia, and many have secondary anhidrosis (summary by Eckl et al., 2005). For a general phenotypic description and discussion of genetic heterogeneity of autosomal recessive congenital ichthyosis, see ARCI1 (242300).

Autosomal recessive hypotrichosis is a condition that affects hair growth. People with this condition have sparse hair (hypotrichosis) on the scalp beginning in infancy. This hair is usually coarse, dry, and tightly curled (often described as woolly hair). Scalp hair may also be lighter in color than expected and is fragile and easily broken. Affected individuals often cannot grow hair longer than a few inches. The eyebrows, eyelashes, and other body hair may be sparse as well. Over time, the hair problems can remain stable or progress to complete scalp hair loss (alopecia) and a decrease in body hair.\n\nRarely, people with autosomal recessive hypotrichosis have skin problems affecting areas with sparse hair, such as redness (erythema), itchiness (pruritus), or missing patches of skin (erosions) on the scalp. In areas of poor hair growth, they may also develop bumps called hyperkeratotic follicular papules that develop around hair follicles, which are specialized structures in the skin where hair growth occurs.

Ischiocoxopodopatellar syndrome (ICPPS) is a rare autosomal dominant disorder characterized by a/hypoplasia of the patellas and various anomalies of the pelvis and feet. Pelvic anomalies include bilateral absent or delayed ossification of the ischiopubic junction and infraacetabular axe cut notches. Other major signs are a wide gap between the first and second toes, short fourth and fifth rays of the feet, and pes planus (summary by Bongers et al., 2001). Pediatric-onset pulmonary arterial hypertension may be seen in association with ICPPS (Kerstjens-Frederikse et al., 2013 and Levy et al., 2016).

Hypotrichosis simplex can affect all body hair or be limited to the scalp. Usually patients with the scalp-limited form of hypotrichosis present with normal hair at birth; they experience a progressive, gradual loss of scalp hair beginning at the middle of the first decade and leading to almost complete loss of scalp hair by the third decade. A few sparse, fine, short hairs remain in some individuals. Body hair, beard, eyebrows, axillary hair, teeth, and nails develop normally. Light and electron microscopy of hairs from early hypotrichosis simplex revealed no structural changes, whereas hairs from patients with advanced hypotrichosis showed focal areas of defective cuticular structure. Men and women are equally affected (summary by Betz et al., 2000). For a discussion of genetic heterogeneity of nonsyndromic hypotrichosis, see 605389.

Hypotrichosis-lymphedema-telangiectasia syndrome is an autosomal recessive disorder characterized by these 3 features, which begin at birth or in early childhood and are progressive (summary by Irrthum et al., 2003).

A rare clinical variant of epidermolytic ichthyosis, with manifestations of blistering phenotype at birth and the development from early infancy of annular polycyclic erythematous scales on the trunk and extremities. It has been reported in less than 10 families. The disease is caused by mutations in the KRT1 (12q11-q13) and KRT10 (17q21-q23) genes, encoding keratins 1 and 10 respectively. These mutations impair keratin filament formation and weaken the structural stability of the keratinocyte cytoskeleton. Transmission is autosomal dominant.

A rare multiple congenital anomalies/dysmorphic syndrome characterized by the association of dysplastic external ears, nail hypoplasia, and variable skeletal malformations, such as hypoplastic or absent fibulae, abnormalities of the scapula, clavicle, and acromioclavicular joint, and talipes equinovarus, among others. Joint contractures and mild facial dysmorphism have also been reported.

PPKS2 is characterized by linear hyperkeratosis of the palms, which is particularly evident in affected individuals who perform manual labor. Hyperkeratosis of the soles primarily involves pressure points, and diffuse background palmoplantar thickening may also be present. (Armstrong et al., 1999; Whittock et al., 1999). For a discussion of genetic heterogeneity of the striate form of palmoplantar keratoderma, see PPKS1 (148700).

Epidermolysis bullosa simplex (EBS) is characterized by fragility of the skin (and mucosal epithelia in some instances) that results in non-scarring blisters and erosions caused by minor mechanical trauma. EBS is distinguished from other types of epidermolysis bullosa (EB) or non-EB skin fragility syndromes by the location of the blistering in relation to the dermal-epidermal junction. In EBS, blistering occurs within basal keratinocytes. The severity of blistering ranges from limited to hands and feet to widespread involvement. Additional features can include hyperkeratosis of the palms and soles (keratoderma), nail dystrophy, milia, and hyper- and/or hypopigmentation. Rare EBS subtypes have been associated with additional clinical features including pyloric atresia, muscular dystrophy, cardiomyopathy, and/or nephropathy.

Metaphyseal dysostosis-intellectual disability-conductive deafness syndrome is characterised by metaphyseal dysplasia, short-limb dwarfism, mild intellectual deficit and conductive hearing loss, associated with repeated episodes of otitis media in childhood. It has been described in three brothers born to consanguineous Sicilian parents. Variable manifestations included hyperopia and strabismus. The mode of inheritance is autosomal recessive.

The syndrome steatocystoma multiplex and natal teeth is characterized by generalized multiple steatocystomas and natal teeth.

Hypotrichosis-5 (HYPT5), also known as Marie Unna hereditary hypotrichosis-2 (MUHH2), is a form of hereditary hypotrichosis characterized by twisting hair. Affected individuals have little or no scalp hair at birth, wiry and irregular scalp hair in childhood, and sparse or no forehead and parietal hair at puberty. Eyebrows and eyelashes are thin, and pubic and axillary hair fails to develop. Scarring alopecia is modest, and vertex hair is normal (summary by Zhang et al., 2012). For a general phenotypic description of Marie Unna hereditary hypotrichosis, see MUHH1 (146550). For a discussion of genetic heterogeneity of nonsyndromic hypotrichosis, see 605389.

Any striate palmoplantar keratoderma in which the cause of the disease is a mutation in the KRT1 gene.

Hypotrichosis simplex can affect all body hair (generalized; see 605389) or be limited to the scalp. Usually patients with the scalp-limited form of hypotrichosis present with normal hair at birth; they experience a progressive, gradual loss of scalp hair beginning at the middle of the first decade and leading to almost complete loss of scalp hair by the third decade. A few sparse, fine, short hairs remain in some individuals. Body hair, beard, eyebrows, axillary hair, teeth, and nails develop normally. Light and electron microscopy of hairs from patients with early hypotrichosis simplex revealed no structural changes, whereas hairs from patients with advanced hypotrichosis showed focal areas of defective cuticular structure. Men and women are equally affected (summary by Betz et al., 2000). For a discussion of genetic heterogeneity of nonsyndromic hypotrichosis, see HYPT1 (605389).

A hypotrichosis that has material basis in an autosomal recessive mutation on chromosome 10q11.23-q22.3.

A hypotrichosis that has material basis in an autosomal recessive mutation on chromosome 7p22.3-p21.3.

Cole disease (COLED) is a rare autosomal dominant disorder characterized by congenital or early-onset punctate keratoderma associated with irregularly shaped hypopigmented macules, which are typically found over the arms and legs but not the trunk or acral regions. Skin biopsies of palmoplantar lesions show nonspecific changes including hyperorthokeratosis, hypergranulosis, and acanthosis. Hypopigmented areas of skin, however, reveal a reduction in melanin content in keratinocytes but not in melanocytes, as well as hyperkeratosis and a normal number of melanocytes. Ultrastructurally, melanocytes show a disproportionately large number of melanosomes in the cytoplasm and dendrites, whereas keratinocytes show a paucity of these organelles, suggestive of impaired melanosome transfer (summary by Eytan et al., 2013). Some patients also exhibit calcinosis cutis or early-onset calcific tendinopathy (Eytan et al., 2013).

Any hypotrichosis in which the cause of the disease is a mutation in the RPL21 gene.

Hereditary hypotrichosis simplex (HHS) is a rare form of nonsyndromic hereditary hypotrichosis without characteristic hair shaft anomalies. Affected individuals typically show normal hair at birth, but hair loss and thinning of the hair shaft start during early childhood and progress with age. HHS can be largely divided into 2 forms: the scalp-limited form (e.g., 146520) and the generalized form, such as HYPT1, in which all body hair is affected. HHS is characterized by progressive hair follicle miniaturization, which is a typical feature of androgenetic alopecia (see 109200). HHS can be inherited either as an autosomal dominant or autosomal recessive trait (e.g., HYPT8, 278150) (summary by Shimomura et al., 2010). Genetic Heterogeneity of Nonsyndromic Hypotrichosis See also HYPT2 (146520), caused by mutation in the CDSN gene (602593) on chromosome 6p21; HYPT3 (613981), caused by mutation in the KRT74 gene (608248) on chromosome 12q13; HYPT4 (146550), caused by mutation in the HRURF gene (619257) on chromosome 8p21; HYPT5 (612841), caused by mutation in the EPS8L3 gene (614989) on chromosome 1p13; HYPT6 (607903), caused by mutation in the DSG4 gene (607892) on chromosome 18q12; HYPT7 (604379), caused by mutation in the LIPH gene (607365) on chromosome 3q27; HYPT8 (278150), caused by mutation in the LPAR6 gene (609239) on chromosome 13q14; HYPT9 (614237), mapped to chromosome 10q11.23-q22.3; HYPT10 (614238), mapped to chromosome 7p22.3-p21.3; HYPT11 (615059), caused by mutation in the SNRPE gene (128260) on chromosome 1q32; HYPT12 (615885), caused by mutation in the RPL21 gene (603636) on chromosome 13q12; HYPT13 (615896), caused by mutation in the KRT71 gene (608245) on chromosome 12q13; HYPT14 (618275), caused by mutation in the LSS gene (600909) on chromosome 21q22; and HYPT15 (620177), caused by mutation in the C3ORF52 gene (611956) on chromosome 3q13.

Severe junctional epidermolysis bullosa 3B (JEB3B) is an autosomal recessive skin blistering disorder characterized by extreme fragility of the skin and epithelia of various extracutaneous tissues. Skin blisters and erosions are present at birth. The plane of skin cleavage is through the lamina lucida of the cutaneous basement membrane zone. Patients die in infancy to early adulthood (summary by Has et al., 2020). For a discussion of genetic heterogeneity of the subtypes of JEB, see JEB1A (226650). Reviews Has et al. (2020) reviewed the clinical and genetic aspects, genotype-phenotype correlations, disease-modifying factors, and natural history of epidermolysis bullosa.