ABSTRACT
PURPOSE: Xeroderma pigmentosum (XP) is an autosomal recessive disease with defective DNA repair, a markedly increased risk of skin cancer, and premature aging. Reports from North Africa have described thyroid nodules in XP patients, but thyroid nodule prevalence has never been determined in XP patients enrolled in our natural history study at the National Institutes of Health (NIH). METHODS: We performed thyroid ultrasound examinations on all 29 XP patients examined from 2011 to 2019 and assessed nodule malignancy using the Thyroid Imaging Reporting and Data System. Thyroid nodule prevalence was also obtained from comparison cohorts. DNA sequencing was performed on thyroid tissue from XP patients who had surgery for thyroid cancer. RESULTS: Thyroid nodules were identified in 18/29 XP patients (62%). The median age of patients with thyroid nodules in our XP cohort (20 years) was younger than that of three comparison groups: 36 years (California study-208 subjects), 48 years (Korean study-24,757 subjects), and 52 years (NIH-682 research subjects). Multiple (2-4) thyroid nodules were found in 12/18 (67%) of the patients with nodules. Autopsy examination revealed follicular adenomas in 4/8 (50%) additional XP patients. DNA sequencing revealed rare mutations in two other XP patients with papillary thyroid cancer. CONCLUSIONS: XP patients have an increased incidence of thyroid nodules at an early age in comparison to the general population. These finding confirm another premature aging feature of XP.
Subject(s)
Aging, Premature/physiopathology , Thyroid Nodule/epidemiology , Xeroderma Pigmentosum/complications , Adolescent , Adult , Child , Female , Follow-Up Studies , Humans , Male , Maryland/epidemiology , Middle Aged , Prognosis , Thyroid Nodule/etiology , Thyroid Nodule/pathology , Young AdultABSTRACT
BACKGROUND: The study of autoinflammatory diseases has uncovered mechanisms underlying cytokine dysregulation and inflammation. METHODS: We analyzed the DNA of an index patient with early-onset systemic inflammation, cutaneous vasculopathy, and pulmonary inflammation. We sequenced a candidate gene, TMEM173, encoding the stimulator of interferon genes (STING), in this patient and in five unrelated children with similar clinical phenotypes. Four children were evaluated clinically and immunologically. With the STING ligand cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), we stimulated peripheral-blood mononuclear cells and fibroblasts from patients and controls, as well as commercially obtained endothelial cells, and then assayed transcription of IFNB1, the gene encoding interferon-ß, in the stimulated cells. We analyzed IFNB1 reporter levels in HEK293T cells cotransfected with mutant or nonmutant STING constructs. Mutant STING leads to increased phosphorylation of signal transducer and activator of transcription 1 (STAT1), so we tested the effect of Janus kinase (JAK) inhibitors on STAT1 phosphorylation in lymphocytes from the affected children and controls. RESULTS: We identified three mutations in exon 5 of TMEM173 in the six patients. Elevated transcription of IFNB1 and other gene targets of STING in peripheral-blood mononuclear cells from the patients indicated constitutive activation of the pathway that cannot be further up-regulated with stimulation. On stimulation with cGAMP, fibroblasts from the patients showed increased transcription of IFNB1 but not of the genes encoding interleukin-1 (IL1), interleukin-6 (IL6), or tumor necrosis factor (TNF). HEK293T cells transfected with mutant constructs show elevated IFNB1 reporter levels. STING is expressed in endothelial cells, and exposure of these cells to cGAMP resulted in endothelial activation and apoptosis. Constitutive up-regulation of phosphorylated STAT1 in patients' lymphocytes was reduced by JAK inhibitors. CONCLUSIONS: STING-associated vasculopathy with onset in infancy (SAVI) is an autoinflammatory disease caused by gain-of-function mutations in TMEM173. (Funded by the Intramural Research Program of the National Institute of Arthritis and Musculoskeletal and Skin Diseases; ClinicalTrials.gov number, NCT00059748.).
Subject(s)
Inflammation/genetics , Membrane Proteins/genetics , Mutation , Skin Diseases, Vascular/genetics , Age of Onset , Cytokines/genetics , Cytokines/metabolism , Female , Fibroblasts/metabolism , Genes, Dominant , Humans , Infant , Infant, Newborn , Inflammation/metabolism , Interferon-gamma/genetics , Interferon-gamma/metabolism , Janus Kinases/antagonists & inhibitors , Lung Diseases/genetics , Male , Pedigree , Phosphorylation , STAT1 Transcription Factor/metabolism , Sequence Analysis, DNA , Skin Diseases, Vascular/metabolism , Syndrome , Transcription, Genetic , Up-RegulationABSTRACT
The effects of DNA repair and transcription gene abnormalities in human pre-natal life have never been studied. Trichothiodystrophy (TTD) is a rare (affected frequency of 10(-6)) recessive disorder caused by mutations in genes involved in nucleotide excision repair (NER) pathway and in transcription. Based on our novel clinical observations, we conducted a genetic epidemiologic study to investigate gestational outcomes associated with TTD. We compared pregnancies resulting in TTD-affected offspring (n = 24) with respect to abnormalities during their antenatal and neonatal periods to pregnancies resulting in their unaffected siblings (n = 18), accounting for correlation, and to population reference values. Significantly higher incidence of several severe gestational complications was noted in TTD-affected pregnancies. Small for gestational age (SGA) <10th percentile [Relative risk (RR ) = 9.3, 95% CI = 1.4-60.5, p = 0.02], SGA <3rd percentile (RR = 7.2, 95% CI = 1.1-48.1, p = 0.04), and neonatal intensive care unit (NICU) hospitalization (RR = 6.4, 95% CI = 1.4-29.5, p = 0.02) occurred more frequently among TTD-affected neonates compared with their unaffected siblings. Compared with reference values from general obstetrical population, pregnancies that resulted in TTD-affected infants were significantly more likely to be complicated by hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome (RR = 35.7, 95% CI = 7.6-92.5, p = 0.0002), elevated mid-trimester maternal serum human chorionic gonadotropin (hCG) levels (RR = 14.3, 95% CI = 7.0-16.6, p < 0.0001), SGA <3rd percentile (RR = 13.9, 95% CI = 7.4-21.1, p < 0.0001), pre-term delivery (<32 weeks) (RR = 12.0, 95% CI = 4.9-21.6, p < 0.0001), pre-eclampsia (RR = 4.0, 95% CI = 1.6-7.4, p = 0.006), and decreased fetal movement (RR = 3.3, 95% CI = 1.6-5.2, p = 0.0018). Abnormal placental development is an underlying mechanism that may explain the constellation of observed complications in our study. Thus, we hypothesize that TTD DNA repair and transcription genes play an important role in normal human placental development.
Subject(s)
DNA Repair/genetics , Fetal Development/genetics , Transcription, Genetic , Trichothiodystrophy Syndromes/embryology , Trichothiodystrophy Syndromes/genetics , Adult , Demography , Family , Female , Humans , Live Birth , Middle Aged , Pregnancy , Pregnancy Outcome , Reference Values , Young AdultABSTRACT
Trichothiodystrophy (TTD) is a rare, autosomal recessive disease, characterised by brittle, sulfur deficient hair and multisystem abnormalities. A systematic literature review identified 112 patients ranging from 12 weeks to 47 years of age (median 6 years). In addition to hair abnormalities, common features reported were developmental delay/intellectual impairment (86%), short stature (73%), ichthyosis (65%), abnormal characteristics at birth (55%), ocular abnormalities (51%), infections (46%), photosensitivity (42%), maternal pregnancy complications (28%) and defective DNA repair (37%). There was high mortality, with 19 deaths under the age of 10 years (13 infection related), which is 20-fold higher compared to the US population. The spectrum of clinical features varied from mild disease with only hair involvement to severe disease with profound developmental defects, recurrent infections and a high mortality at a young age. Abnormal characteristics at birth and pregnancy complications, unrecognised but common features of TTD, suggest a role for DNA repair genes in normal fetal development.
Subject(s)
Hair/abnormalities , Trichothiodystrophy Syndromes/pathology , Adolescent , Adult , Birth Weight , Body Height , Child , Child, Preschool , DNA Repair/physiology , Developmental Disabilities/epidemiology , Eye Diseases/epidemiology , Eye Diseases/microbiology , Female , Genes, Recessive , Gonadal Dysgenesis/epidemiology , Hair/chemistry , Humans , Ichthyosis/epidemiology , Infant , Male , Middle Aged , Photosensitivity Disorders/epidemiology , Prevalence , Trichothiodystrophy Syndromes/genetics , Trichothiodystrophy Syndromes/microbiologyABSTRACT
Patients with the rare genetic disorders, xeroderma pigmentosum (XP), trichothiodystrophy (TTD) and Cockayne syndrome (CS) have defects in DNA nucleotide excision repair (NER). The NER pathway involves at least 28 genes. Three NER genes are also part of the basal transcription factor, TFIIH. Mutations in 11 NER genes have been associated with clinical diseases with at least eight overlapping phenotypes. The clinical features of these patients have some similarities but also have marked differences. NER is involved in protection against sunlight-induced DNA damage. While XP patients have 1000-fold increase in susceptibility to skin cancer, TTD and CS patients have normal skin cancer risk. Several of the genes involved in NER also affect somatic growth and development. Some patients have short stature and immature sexual development. TTD patients have sulfur deficient brittle hair. Progressive sensorineural deafness is an early feature of XP and CS. Many of these clinical diseases are associated with developmental delay and progressive neurological degeneration. The main neuropathology of XP is a primary neuronal degeneration. In contrast, CS and TTD patients have reduced myelination of the brain. These complex neurological abnormalities are not related to sunlight exposure but may be caused by developmental defects as well as faulty repair of DNA damage to neuronal cells induced by oxidative metabolism or other endogenous processes.
Subject(s)
Cockayne Syndrome/genetics , DNA Damage/genetics , DNA Repair/genetics , Mutation/genetics , Xeroderma Pigmentosum/genetics , Brain Diseases, Metabolic, Inborn/genetics , Brain Diseases, Metabolic, Inborn/metabolism , Brain Diseases, Metabolic, Inborn/physiopathology , Cockayne Syndrome/metabolism , Cockayne Syndrome/physiopathology , Heredodegenerative Disorders, Nervous System/genetics , Heredodegenerative Disorders, Nervous System/metabolism , Heredodegenerative Disorders, Nervous System/physiopathology , Humans , Phenotype , Skin Diseases, Genetic/genetics , Skin Diseases, Genetic/metabolism , Skin Diseases, Genetic/physiopathology , Xeroderma Pigmentosum/metabolism , Xeroderma Pigmentosum/physiopathologyABSTRACT
Raman spectra of normal hair shafts and hair shafts from patients exhibiting trichothiodystrophy (TTD) were obtained using line focus laser illumination. Because hair from TTD patients has a significant decrease in the content of the sulfur-containing amino acids in comparison to normal hair, the 550-500 cm(-1) disulfide stretching mode region of the Raman spectrum was examined in detail. A quantitative spectral analysis demonstrates significant increases in the two energetically less favored gauche-gauche-trans (g-g-t) and trans-gauche-trans (t-g-t) forms. These observations suggest that the increased amounts of these less stable disulfide conformers are contributing factors to or associated with the hair brittleness observed for this congenital disorder. Structure-spectra correlations for the three dominant disulfide conformers are confirmed by quantum chemical calculations using modern density functional theory (DFT).
Subject(s)
Hair Diseases/metabolism , Hair/chemistry , Proteins/chemistry , Biopolymers/chemistry , DNA Repair/genetics , Disulfides/chemistry , Hair/pathology , Hair Diseases/genetics , Hair Diseases/pathology , Humans , Models, Molecular , Protein Conformation , Spectrum Analysis, RamanABSTRACT
Isotretinoin has demonstrated efficacy in a wide range of disorders. The beneficial effects of the drug, however, are limited by its adverse effects on the bone. Children exposed to high doses are at risk for premature epiphyseal closure, while adults on long-term therapy have an increased tendency to develop hyperstosis and other changes of the bone. The knowledge of these effects, in conjunction with continued surveillance, are necessary for expert management and can ensure many years of efficacious treatment with minimal toxicity.
Subject(s)
Dermatologic Agents/adverse effects , Hyperostosis, Diffuse Idiopathic Skeletal/chemically induced , Hyperostosis/chemically induced , Isotretinoin/adverse effects , Acne Vulgaris/drug therapy , Adolescent , Adult , Age Factors , Bone Development/drug effects , Child , Child, Preschool , Dermatologic Agents/therapeutic use , Growth Plate/drug effects , Growth Plate/growth & development , Humans , Isotretinoin/therapeutic useABSTRACT
OBJECTIVE: To assess the reliability of counts of actinic keratoses (AKs) and the effect of a brief joint discussion of discrepancies on that reliability. DESIGN AND INTERVENTION: Seven dermatologists independently counted AKs on the face and ears before and after a brief joint discussion of discrepancies. SETTING AND PATIENTS: A volunteer sample of 9 patients from the ongoing VA (Department of Veterans Affairs) Topical Tretinoin Chemoprevention (VATTC) Trial. All participating individuals are veterans and have had 2 or more keratinocyte carcinomas (basal or squamous cell carcinoma) in the 5 years before enrollment in the study. MAIN OUTCOME MEASURE: Standard deviation of estimates of the Poisson regression parameter for the dermatologists. RESULTS: Substantial variation was found among the dermatologists in their AK counts. The SD of the parameter estimates for the dermatologists decreased from 0.45 to 0.24 after the brief joint discussion, a 47% decrease (P =.076). The variation attributable to the dermatologists also decreased substantially (chi(2)(6) decrease, 94 to 12). CONCLUSIONS: Actinic keratoses are common, and there is a continuous spectrum of lesions that ranges from sun-damaged skin to squamous cell carcinoma in situ. Clinical distinguishing features may be difficult to delineate precisely. Counts of AK are commonly performed, but appear to be unreliable, even when performed by experienced dermatologists. Joint discussion of discrepancies may enhance the reliability of these counts, although substantial variation remains. Research that relied on these counts must be reevaluated in light of the marked variation among expert observers. Future studies should consider measures to assess and enhance reliability.
Subject(s)
Keratolytic Agents/administration & dosage , Keratosis/pathology , Keratosis/prevention & control , Photosensitivity Disorders/pathology , Photosensitivity Disorders/prevention & control , Tretinoin/administration & dosage , Aged , Aged, 80 and over , Humans , Keratosis/complications , Middle Aged , Photosensitivity Disorders/complications , Randomized Controlled Trials as Topic , Reproducibility of ResultsABSTRACT
Changes in body weight and the incidence of estrogen-related side effects with low-dose oral contraceptives (OCs) containing 20 microg ethinyl estradiol (EE) have not been demonstrated in placebo-controlled trials. Two placebo-controlled, randomized trials demonstrated the efficacy of a low-dose OC for the treatment of acne in healthy females (n = 704; >or=14 years old) with regular menstrual cycles and moderate facial acne. Patients were randomized to receive 20 microg EE/100 microg levonorgestrel (LNG) or placebo for six cycles. Body weight was measured at baseline and during Cycles 1, 3, and 6. The occurrence of adverse events was recorded at each visit. Mean changes in weight from baseline were similar with 20 microg EE/100 microg LNG [0.72 kg +/- 2.64 (SD; n = 349)] and placebo [0.56 kg +/- 2.64 (SD; n = 355; p > 0.05)] for the last measured weight of each patient. Rates of headache, nausea, weight gain, and breast pain, side effects commonly attributed to OCs, were also similar between groups (p > 0.05). No serious, unexpected, drug-related adverse events occurred during the study. The low-dose OC containing 20 microg EE/100 microg LNG is safe, well tolerated, and does not cause weight gain.
Subject(s)
Body Weight/drug effects , Contraceptives, Oral/administration & dosage , Contraceptives, Oral/adverse effects , Ethinyl Estradiol/administration & dosage , Ethinyl Estradiol/adverse effects , Levonorgestrel/administration & dosage , Levonorgestrel/adverse effects , Adolescent , Adult , Blood Pressure/drug effects , Female , Humans , Middle Aged , PregnancyABSTRACT
Retinoids are a fascinating class of compounds that exert control over cellular function from the time of conception to death. They play a critical role in such vital processes as fetal morphogenesis, cellular differentiation and apoptosis. Over the years synthetic retinoids have provided dermatologists with a spectrum of medications that have profound therapeutic effects on a variety of recalcitrant skin disorders. Moreover, retinoids are an expanding component of the treatment arsenal against hematologic and solid malignancies. Retinoids are poised to offer exciting new therapeutic options in the field of endocrinology for the treatment of diabetes and lipid disorders. Researchers and clinicians are only beginning to unveil the therapeutic potential of this class of medications. The development of new retinoid compounds targeting specific receptors promises a wealth of new therapies for the new millennium.
Subject(s)
Tretinoin/therapeutic use , Vitamin A/therapeutic use , Acne Vulgaris/drug therapy , Humans , Keratosis/drug therapy , Leukemia, Promyelocytic, Acute/drug therapy , Lymphoma, T-Cell, Cutaneous/drug therapy , Psoriasis/drug therapy , Skin Neoplasms/drug therapy , Treatment Outcome , Tretinoin/adverse effects , Vitamin A/adverse effectsABSTRACT
The Comèl-Netherton syndrome is an autosomal recessive multisystemic disorder characterized by localized or generalized congenital ichthyosis, hair shaft abnormalities, immune deficiency, and markedly elevated IgE levels. Life-threatening complications during infancy include temperature and electrolyte imbalance, recurrent infections, and failure to thrive. To study the clinical presentations of the Comèl-Netherton syndrome and its molecular cause, we ascertained 19 unrelated families of various ethnic backgrounds. Results of initial linkage studies mapped the Comèl-Netherton syndrome in 12 multiplex families to a 12 cM interval on 5q32, thus confirming genetic homogeneity of Comèl-Netherton syndrome across families of different origins. The Comèl-Netherton syndrome region harbors the SPINK5 gene, which encodes a multidomain serine protease inhibitor (LEKTI) predominantly expressed in epithelial and lymphoid tissues. Recently, recessive mutations in SPINK5 were identified in several Comèl-Netherton syndrome patients from consanguineous families. We used heteroduplex analysis followed by direct DNA sequencing to screen all 33 exons and flanking intronic sequences of SPINK5 in the affected individuals of our cohort. Mutation analysis revealed 17 distinct mutations, 15 of which were novel, segregating in 14 Comèl-Netherton syndrome families. The nucleotide changes included four non-sense mutations, eight small deletions or insertions leading to frameshift, and five splice site defects, all of which are expected to result in premature terminated or altered translation of SPINK5. Almost half of the mutations clustered between exons 2 and 8, including two recurrent mutations. Genotype-phenotype correlations suggested that homozygous nucleotide changes resulting in early truncation of LEKT1 are associated with a severe phenotype. For the first time, we used molecular data to perform prenatal testing, thus demonstrating the feasibility of molecular diagnosis in the Comèl-Netherton syndrome.
Subject(s)
Carrier Proteins , Gene Deletion , Hair/abnormalities , Ichthyosiform Erythroderma, Congenital/genetics , Prenatal Diagnosis , Serine Proteinase Inhibitors/genetics , Adolescent , Adult , Child , Child, Preschool , Codon, Nonsense , DNA Mutational Analysis , DNA Primers , Dermatitis, Atopic/genetics , Family Health , Female , Genetic Linkage , Heteroduplex Analysis , Humans , Infant , Male , Middle Aged , Molecular Sequence Data , Phenotype , Pregnancy , Proteinase Inhibitory Proteins, Secretory , Serine Peptidase Inhibitor Kazal-Type 5ABSTRACT
Patients who develop large numbers of skin cancers suffer increased morbidity and mortality. A high skin cancer risk can result from inherited disorders such as xeroderma pigmentosum (abnormal repair of UV-induced DNA damage) or the nevoid basal cell carcinoma syndrome (tumor suppressor gene abnormality). The efficacy of systemic retinoid skin cancer chemoprevention was first demonstrated in these disorders. Since the mechanism of cancer prevention was not thought to involve correction of the underlying defect causing the disorder, individuals at high risk for new skin cancers from other causes may also benefit from this approach. With the success of organ transplantation, there is a growing population of transplant recipients living long, active lives who also have sustained chronic UV damage. This population is at high risk for developing aggressive squamous cell carcinomas. In this population, extensive skin involvement with human papilloma virus induced warts and actinic keratoses results in difficulty with diagnosis and monitoring for these dangerous malignancies. Patients who have received treatment with agents that cause DNA damage, such as X-radiation, may also have a high skin cancer risk. Retinoid chemoprevention may also be of benefit in the management of selected patients with these iatrogenic conditions. This evolving therapeutic role has heightened the need for the development of new retinoids, with more efficacy and less toxicity, for cancer chemoprevention.
Subject(s)
Neoplasms, Radiation-Induced/prevention & control , Retinoids/therapeutic use , Skin Neoplasms/prevention & control , Genetic Predisposition to Disease , Humans , Skin Neoplasms/genetics , Xeroderma Pigmentosum/geneticsABSTRACT
Darier disease (DD) is with a frequency of up to 1 in 36,000 a relatively common genodermatosis with autosomal dominant inheritance and late age of onset. The progressive skin manifestations are variable, but often debilitating and disfiguring, and may be associated with a wide range of neuropsychiatric problems, such as epilepsy and depression. On histology, acantholysis and dyskeratosis are prominent findings, implicating impaired functionality of desmosomes. Recently, mutations in the ATP2A2 gene encoding SERCA2, a calcium pump of the endo/sacrcoplasmic reticulum, have been identified as the molecular basis of DD. This slow-twitched calcium ATPase has two splice variants, one of which is highly expressed in epidermis, and maintains low intracellular calcium levels by facilitating transport of cytosolic calcium into the endoplasmic reticulum. Thus, it may confer a direct effect on the established calcium-dependent assembly of desmosomes. We screened ATP2A2 in a cohort of 24 DD families using conformation sensitive gel electrophoresis and direct sequencing, and detected 14 distinct mutations, 9 of which were novel. The mutational spectrum included 9 missense mutations, 1 nonsense mutation, 3 small in-frame deletions, and a 19-basepair insertion. Mutations were scattered over the entire gene with a slight preponderance in the first 8 exons, and affected exclusively residues conserved among all SERCAs. In addition, we found 2 silent polymorphisms, 1 of which occurred in 4 unrelated families. Comparison of molecular data and phenotypic features, such as severity and type of disease, occurrence of mucosal involvement, or association with neuropsychiatric disorders, did not reveal an obvious genotype-phenotype correlation in our cohort.
Subject(s)
Calcium-Transporting ATPases/genetics , Darier Disease/genetics , Mutation , Cohort Studies , DNA Mutational Analysis , DNA Primers/chemistry , Darier Disease/pathology , Electrophoresis, Agar Gel , Genotype , Humans , Isoenzymes/genetics , Phenotype , Polymerase Chain Reaction , Sarcoplasmic Reticulum Calcium-Transporting ATPasesABSTRACT
Systemic retinoids represent a growing armamentarium in the treatment of a wide range of skin disorders and malignancies. Although these drugs can have substantial toxicities, their wise use can result in safe and efficacious therapy that can alter dramatically the lives of individuals with severe skin disorders.
Subject(s)
Retinoids/administration & dosage , Skin Diseases/drug therapy , Acne Vulgaris/drug therapy , Anticarcinogenic Agents/therapeutic use , Humans , Isotretinoin/administration & dosage , Isotretinoin/adverse effects , Isotretinoin/therapeutic use , Psoriasis/drug therapy , Retinoids/adverse effects , Retinoids/therapeutic use , Skin Neoplasms/drug therapy , Skin Neoplasms/prevention & controlABSTRACT
Examination of the skin and nails can reveal many abnormalities in patients with end-stage renal disease that precede or follow initiation of dialysis treatment or kidney transplantation. This article focuses on specific and nonspecific cutaneous signs of end-stage renal disease, reviewing both banal and life-threatening conditions, including pruritus, perforating disorders, calcifying disorders, and bullous dermatoses. The pathogenesis, clinical findings, histologic findings, differential diagnosis, and treatment of these diseases are discussed. Cutaneous manifestations unique to kidney transplantation will not be covered. (J Am Acad Dermatol 2000;43:975-86.)
Subject(s)
Kidney Failure, Chronic/complications , Skin Diseases/diagnosis , Skin Diseases/etiology , Female , Humans , Incidence , Kidney Failure, Chronic/diagnosis , Male , Prognosis , Risk Assessment , Skin Diseases/epidemiologyABSTRACT
Lamellar ichthyosis (LI, OMIM no. 242300) is a severe autosomal recessive genodermatosis with an estimated prevalence of 1:200,000. LI represents one end of the spectrum of congenital recessive ichthyosis (CRI). Mutations in the gene for transglutaminase-1 (TGM1) are responsible for many cases of LI and occur throughout the coding sequence of the gene. Our analyses of patients with CRI revealed a common TGM1 mutation involving loss of the intron 5 splice acceptor site leading to alternative splicing of the message. We found families in which the splice acceptor site mutation was homozygous, and families where the patients were compound heterozygotes for the splice acceptor site mutation and another TGM1 mutation. A mutation at this same site occurs in the majority of Norwegian patients as a founder effect. In our ethnically diverse patient population, none of whom have known Norwegian ancestry, haplotype analysis of the TGM1 chromosomal region also suggested the existence of a founder effect. Comparison of the common haplotype in our data with the Norwegian data showed that 2/7 of our splice acceptor site mutation chromosomes had the full reported Norwegian haplotype, and the remaining five chromosomes exhibited recombination at the most distal marker studied. History, family origins, and haplotype analysis suggested that the mutation originally arose on a German background and was introduced into Norway around 800-1000 AD. We also found a limited correlation between genotype and phenotype in our study, with the four homozygous patients having less severe disease than many of the heterozygotes, and no patient with a splice acceptor site mutation having erythroderma or a congenital ichthyosiform erythroderma phenotype.