Familial acanthosis nigricans with p.K650T FGFR3 mutation

Manifestations and etiology of cutaneous findings in cases of morbid obesity

Morbid obesity is associated with a wide range of metabolic, infective, and organic disorders related to adipose tissue overload. While careful documentation of internal autopsy findings is usual, skin manifestations may be overlooked. Skin manifestations are quite diverse and include striae distensae, skin tags, plantar hyperkeratosis, acanthosis nigricans, the sequelae of hyperandrogenism, lymphedema, panniculus morbidus, chronic venous insufficiency, stasis dermatitis, leg ulceration, intertrigo, cellulitis, pressure ulcers and 'buried penis'. Obesity has also been associated with hidradenitis suppurativa, psoriasis, atopic dermatitis, melanoma, systemic lupus erythematosus, lichen planus and acne vulgaris. Evaluating these findings at the time of autopsy may give a more complete assessment of a particular case and may also identify conditions that may have contributed to, or caused, death.

Acanthosis Nigricans: An Updated Review

BACKGROUND

Early recognition of acanthosis nigricans is important because acanthosis nigricans can be a cutaneous manifestation of a variety of systemic disorders and, rarely, as a sign of internal malignancy.

OBJECTIVE

The purpose of this article is to familiarize pediatricians with the clinical manifestations, evaluation, diagnosis, and management of acanthosis nigricans.

METHODS

A search was conducted in November 2021in PubMed Clinical Queries using the key term "acanthosis nigricans". The search strategy included all clinical trials, observational studies, and reviews published within the past 10 years. Only papers published in the English literature were included in this review. The information retrieved from the above search was used in the compilation of the present article.

RESULTS

Acanthosis nigricans is characterized by symmetric, hyperpigmented, and velvety plaques with ill-defined borders, typically involving intertriginous areas. Obesity is the most common cause of acanthosis nigricans which is increasingly observed in obese children and adolescents and can serve as a cutaneous marker of insulin resistance. Early recognition of acanthosis nigricans is important because acanthosis nigricans can also be a cutaneous manifestation of a variety of systemic disorders and, rarely, as a sign of internal malignancy. This may consist of weight reduction, discontinuation of causative drugs, treatment of underlying endocrinopathy, or treatment of an underlying malignancy. For patients with isolated acanthosis nigricans and for those whose underlying cause is not amenable to treatment, treatment of the lesion may be considered for cosmetic reasons. Topical retinoids, vitamin D analogs, chemical peels, and other keratolytics are often used for the treatment of localized lesions. Seldom, systemic therapy such as oral retinoids may be considered for extensive or generalized acanthosis nigricans and acanthosis nigricans unresponsive to topical therapy. Other uncommon treatment modalities include dermabrasion, laser therapy, and surgical removal.

CONCLUSION

Although acanthosis nigricans is treatable, a complete cure is difficult to achieve. The underlying cause should be treated, if possible, to resolve and prevent the recurrence of acanthosis nigricans. The diagnosis is mainly clinical, based on the characteristic appearance (symmetrically distributed, hyperpigmented, velvety, papillomatous, hyperkeratotic plaques with ill-defined borders) and the typical sites (intertriginous areas, flexural area, and skin folds) of the lesions. The diagnosis might be difficult for lesions that have atypical morphology or are in an unusual location. Clinicians should be familiar with the clinical signs, evaluation, diagnosis, and therapy of acanthosis nigricans because of the link between it and underlying diseases.

Acanthosis nigricans: A review

BACKGROUND

Acanthosis nigricans (AN) is a cutaneous disorder characterized by symmetric velvety hyperpigmented plaques on intertriginous areas like axilla, neck, inframammary, and groin.

AIMS

To summarize the pathophysiology and classification of AN, provide an update of diagnostic testing strategies, and describe the current therapeutic options described so far in the literature for this disease.

METHODS

A comprehensive english language literature search across multiple databases (PubMed, EMBASE, MEDLINE, and Cochrane) for keywords (alone and in combination) was performed. MeSH as well as non-MeSH terms such as "acanthosis nigricans," "classification," "pathophysiology," "diagnosis," "treatment," "topical drugs," "systemic drugs," "chemical peeling," and "lasers" were taken into consideration.

RESULTS

The pathophysiology of AN revolves around a multifactorial stimulation of proliferation of epidermal keratinocytes and dermal fibroblasts. Various types of AN include benign, obesity-associated, syndromic, malignant, acral, unilateral, medication-induced, and mixed-type. Homeostasis model assessment-insulin resistance (HOMA-IR) is a good tool for assessment of insulin resistance. Management involves general measures (weight reduction and addressing the underlying cause, if any), topical drugs (retinoids, vitamin D analogs, and keratolytics), oral drugs (retinoids and insulin sensitizers), chemical peels (trichloroacetic acid), and lasers (Long pulsed alexandrite, fractional 1550-nm erbium fiber, and CO₂ ).

CONCLUSION

Acanthosis nigricans is a treatable condition; however, complete cure and disappearance of lesions are difficult to achieve. Weight reduction is the most scientific and practical management strategy. Long-term studies and further research is warranted in the pathophysiology and treatment of this common condition.

Autosomal dominant familial acanthosis nigricans caused by a C-terminal nonsense mutation of FGFR3

FGFR3 encodes a transmembrane receptor tyrosine kinase that has six autophosphorylation sites of tyrosine. Among them, Y770 is a negative regulatory site for the downstream signaling of FGFR3. Constitutive active mutations in FGFR3 are involved in human developmental disorders including familial acanthosis nigricans, an autosomal dominant disorder characterized by general hyperpigmentation with mild acanthosis of the epidermis. Here, we report two unrelated cases of familial acanthosis nigricans with a heterozygous c.2302G>T (p.E768*) mutation in FGFR3 (NM_000142.5). FGFR3 mRNA purified from the skin lesion neither showed aberrant splicing nor nonsense-mediated mRNA decay, indicating that the FGFR3 mutant simply lacked the C-terminal 768-806 amino acids including Y770. While all of the known pathogenic mutations were missense mutations in FGFR3 showing autosomal dominant trait, the c.2302G>T mutation of FGFR3 is a unique autosomal dominant nonsense mutation that causes familial acanthosis nigricans probably via loss of negative regulatory autophosphorylation site of FGFR3.

Crouzon Syndrome and Acanthosis Nigricans With Fibrous Dysplasia of the Maxilla: An Unreported Suggested Triad

ABSTRACT

The aim of this report is to describe the combination of Crouzon syndrome and acanthosis nigricans with fibrous dysplasia of the maxilla. The diagnosis of fibrous dysplasia was confirmed clinically and pathologically during Le Fort III osteotomy and midface advancement with distraction osteogenesis. Crouzon syndrome with acanthosis nigricans is a known syndrome with an incidence of 1:1,000,000. This is the first report in the literature of Crouzon syndrome and acanthosis nigricans combined with fibrous dysplasia. As all 3 pathologies are related to fibroblasts, they may be different manifestations of malfunction of a single molecular pathway. The detection of fibrous dysplasia in a patient with Crouzon syndrome and acanthosis nigricans is important because it may complicate midface osteotomies and fixation of the hardware on the bones during craniofacial surgery.

Acanthosis nigricans in childhood: A cutaneous marker that should not be underestimated, especially in obese children

AIM

The occurrence of acanthosis nigricans (AN) in childhood should not be underestimated since it acts as a cutaneous marker of underlying diseases, such as insulin resistance, endocrinopathy, syndromes and malignancy. The purpose of this review was to highlight the clinical significance of AN in childhood and draw attention to its possible role as early marker of alterations in glucose metabolism in obese children.

METHODS

The Cochrane Library and PubMed databases were searched for papers published in English up to April 2019. Observational studies, case reports and reviews from 1994 to 2019 were included.

RESULTS

Most of the cases of AN are associated with obesity. The prevalence of obesity is rising worldwide and is paralleled by global increases in the prevalence of metabolic syndrome in children. Insulin resistance and AN are closely associated. Evidence indicates that AN is a useful clinical marker for the identification of obese and overweight children and adolescents with insulin resistance who are susceptible to type 2 diabetes mellitus and metabolic syndrome.

CONCLUSION

In clinical practice, the recognition of AN is useful for an early identification of children and adolescents, prone to the insulin-resistant obese phenotype, who could benefit from early interventions.

p.Ser348Cys mutation in FGFR3 gene leads to "Mild ACH /Severe HCH" phenotype

Achondroplasia (ACH) and hypochondroplasia (HCH) are genetic bone disorders known to be caused by gain-of-function mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. Both conditions share radiographic and phenotypical features. HCH is a milder form of ACH. Most individuals with ACH have the recurrent mutation (p.Gly380Arg) in the transmembrane (TM) domain of the receptor and individuals with HCH show the common mutation (p.Asn540Lys) in the tyrosine kinase 1 (TK1) region. Other rare mutations have been reported, however no additional hot-spot has been identified. We report an 8-month-old infant, with the heterozygous mutation, c.1043C > G, leading to an amino acid change from serine at 348 to cysteine (p.Ser348Cys). Clinical diagnosis of the patient is intertwined with "mild ACH" or "severe HCH". He did not demonstrate acanthosis nigricans (AN). This mutation has been reported in two different patients and it is located in the Ig-III domain of the FGFR3 region near other mutations associated with ACH. Among the two the 8-year old one also demonstrated AN without evindece of hyperinsulinem. This report emphasizes the benefit of whole gene sequencing for FGFR3 in individuals with suspected "mild ACH/severe HCH". This child will be monitored for future occurrence of AN.

Acanthosis nigricans, hypochondroplasia, and FGFR3 mutations: Findings with five new patients, and a review of the literature

Early development of extensive acanthosis nigricans (AN) is a key feature in some patients who have hypochondroplasia (HCH) in association with FGFR3 mutations. We here report regarding five new patients with HCH who exhibited AN, and we compare their characteristics to the eight patients previously described in the literature. In these patients, the AN lesions began in childhood, and they were extensive. These lesions were located on the torso, the abdomen, and the face, in addition to the typical skin fold sites. Other skin lesions were frequently reported: café-au-lait macules, melanocytic nevi, lentigines, and seborrheic keratosis. The Lys650Thr mutation was the predominant reported mutation of FGFR3.

Cutaneous paraneoplastic syndromes

A variety of cutaneous abnormalities can be seen in patients with malignant diseases, some of which are infectious, with others representing direct involvement of the skin by the underlying disorder. Yet another group of lesions can be regarded as associated markers of the malignant process, and, as such, are termed "paraneoplastic." This review considers the latter collection of conditions, grouping them by the generic type of malignancy that is usually linked to the paraneoplasia. Some of the processes show a predominant association with alimentary tract malignancies (acanthosis nigricans, acrodermatitis paraneoplastica, florid cutaneous papillomatosis, necrolytic migratory erythema, palmoplantar keratoderma, pancreatic fat necrosis, and pityriasis rotunda). Others are usually linked to a hematolymphoid malignancy (acquired ichthyosis, exfoliative erythroderma, necrobiotic xanthogranuloma, pemphigus paraneoplastica, plane xanthoma, pyoderma gangrenosum, scleromyxedema, Sweet syndrome, and leukocytoclastic vasculitis). Finally, yet another collection of paraneoplastic skin disorders can associate themselves with anatomically-diverse malignancies (Leser-Trelat syndrome, Trousseau syndrome, dermatomyositis, erythema gyratum repens, hypertrichosis lanuginosa acquisita, papuloerythroderma of Ofuji, tripe palms, and multicentric reticulohistiocytosis). Recognition of these processes by the pathologist can be a valuable step in the characterization of underlying malignant diseases.

Achondroplasia: a comprehensive clinical review

Achondroplasia is the most common of the skeletal dysplasias that result in marked short stature (dwarfism). Although its clinical and radiologic phenotype has been described for more than 50 years, there is still a great deal to be learned about the medical issues that arise secondary to this diagnosis, the manner in which these are best diagnosed and addressed, and whether preventive strategies can ameliorate the problems that can compromise the health and well being of affected individuals. This review provides both an updated discussion of the care needs of those with achondroplasia and an exploration of the limits of evidence that is available regarding care recommendations, controversies that are currently present, and the many areas of ignorance that remain.

Acanthosis nigricans in achondroplasia

Acanthosis nigricans (AN) in those with achondroplasia has been reported occasionally in the literature previously. Other disorders arising from constitutive activation of FGFR3 also manifest AN at various frequencies. We assessed the prevalence of AN in a sequential series of 477 individuals with achondroplasia. Using a REDCap database, we collected and analyzed what other features or medical issues may co-occur with AN in those with achondroplasia. AN arises in approximately 10% of individuals with achondroplasia. It usually first appears in preadolescence or adolescence, is more likely in the non-White population and in those who are obese. It is not severe and generally will need no treatment. It is not associated with any evident risk for neither hyperinsulinemic states nor malignancy, and therefore, no special investigations are warranted when it is recognized. Thus, clinicians should not be surprised or concerned upon discovering this finding in those with achondroplasia. In addition, the mechanisms and genetic causes of AN are detailed.