Demonstration of McCune-Albright mutations in the liver of children with high gammaGT progressive cholestasis

Neonatal cholestasis as the onset symptom of McCune-Albright syndrome: case reports and a literature review

Aim

This study aimed to summarize and show the characteristics and evolutionary process of neonatal cholestasis caused by McCune-Albright syndrome (MAS), as neonatal cholestasis may be the initial manifestation of MAS before other classic clinical features appear.

Methods

The clinical characteristics, treatment methods, and outcomes of three neonatal cholestasis cases caused by MAS in our center were retrospectively studied. In addition, all the reported cases of MAS combined with cholestasis were reviewed and summarized to show the cholestatic features in them.

Results

We have confirmed three MAS cases in our center, presenting onset symptoms of jaundice, pale stool, and neonatal cholestasis soon after birth. The cholestasis subsided spontaneously at around the sixth month. The literature review showed that the levels of total bilirubin, conjugated bilirubin, ALT, AST, and GGT in neonatal MAS cholestasis cases were 207 μmol/L (range 65-445 μmol/L), 162 μmol/L (range 46-412 μmol/L), 821 U/L (range 85-3,597 U/L), 532 U/L (range 127-3,633 U/L), and 244 U/L (range 79-3,800 U/L), respectively. Liver histology showed canalicular and hepatocellular cholestasis, giant hepatic cell transformation, and bile paucity. Extrahepatic manifestations such as café-au-lait pigmented skin lesions, Cushing's syndrome, hyperthyroidism, renal tubular dysfunction, and skeletal abnormalities could occur simultaneously when jaundice occurred. GNAS mutations had a high positive rate (83.3%-100%) in liver tissue with cholestasis. Neonatal cholestasis caused by MAS could be self-resolved, but hepatic lesions persist and have malignant potential.

Conclusion

MAS can be one of the causes of neonatal cholestasis, which may be the first manifestation of the disease. Extrahepatic coexisting symptoms of MAS and liver histology can help to distinguish MAS from other etiology of cholestasis. Detecting GNAS mutations in liver tissue may shorten diagnostic time and is of particular interest in the partial and atypical forms of MAS with neonatal cholestasis. Neonatal cholestasis in children with MAS can self-resolve, but liver dysfunction and malignant lesions persist.

Case Report: Severe McCune-Albright syndrome presenting with neonatal Cushing syndrome: navigating through clinical obstacles

Background

Café-au-lait skin macules, Cushing syndrome (CS), hyperthyroidism, and liver and cardiac dysfunction are presenting features of neonatal McCune-Albright syndrome (MAS), CS being the rarest endocrine feature. Although spontaneous resolution of hypercortisolism has been reported, outcome is usually unfavorable. While a unified approach to diagnosis, treatment, and follow-up is lacking, herein successful treatment and long-term follow-up of a rare case is presented.

Clinical case

An 11-day-old girl born small for gestational age presented with deterioration of well-being and weight loss. Large hyperpigmented macules on the trunk, hypertension, hyponatremia, hyperglycemia, and elevated liver enzymes were noted. ACTH-independent CS due to MAS was diagnosed. Although metyrapone (300 mg/m2/day) was started on the 25th day, complete remission could not be achieved despite increasing the dose up to 1,850 mg/m2/day. At 9 months, right total and left three-quarters adrenalectomy was performed. Cortisol decreased substantially, ACTH remained suppressed, rapid tapering of hydrocortisone to physiological dose was not tolerated, and supraphysiological doses were required for 2 months. GNAS analysis from the adrenal tissue showed a pathogenic heterozygous mutation. During 34 months of follow-up, in addition to CS due to MAS, fibrous dysplasia, hypophosphatemic rickets, and peripheral precocious puberty were detected. She is still regularly screened for other endocrinopathies.

Conclusion

Neonatal CS due to MAS is extremely rare. Although there is no specific guideline for diagnosis, treatment, or follow-up, addressing side effects and identifying treatment outcomes will improve quality of life and survival.

Brain and eye involvement in McCune-Albright Syndrome: clinical and translational insights

McCune-Albright Syndrome (MAS) is a rare mosaic (post-zygotic) genetic disorder presenting with a broad continuum clinical spectrum. MAS arises from somatic, activating mutations in the GNAS gene, which induces a dysregulated Gsα-protein signaling in several tissues and an increased production of intracellular cyclic adenosine monophosphate (cAMP). Overall, MAS is a rare disorder affecting less than 1/100,000 children and, for this reason, data establishing genotype-phenotype correlations remain limited. Affected individuals clinically present with a variable combination of fibrous dysplasia of bone (FD), extra-skeletal manifestations (including cafeí-au-lait spots) and precocious puberty which might also be associated to broad hyperfunctioning endocrinopathies, and also gastrointestinal and cardiological involvement. Central nervous system (CNS) and eye involvement in MAS are among the less frequently described complications and remain largely uncharacterized. These rare complications mainly include neurodevelopmental abnormalities (e.g., delayed motor development, cognitive and language impairment), CNS anomalies (e.g., Chiari malformation type I) and a wide array of ophthalmological abnormalities often associated with vision loss. The pathophysiological mechanisms underlying abnormal neurological development have not been yet fully elucidated. The proposed mechanisms include a deleterious impact of chronically dysregulated Gsα-protein signaling on neurological function, or a secondary (damaging) effect of (antenatal and/or early postnatal) hypercortisolism on early pre- and post-natal CNS development. In this Review, we summarize the main neurological and ophthalmological features eventually associated with the MAS spectrum, also providing a detailed overview of the potential pathophysiological mechanisms underlying these clinical complications.

A case report of McCune –Albright syndrome with hepatic manifestations

McCune–Albright syndrome is a non‐hereditary disease characterized by café‐au‐lait skin spots, fibrous dysplasia of bone, and endocrinopathies. We report a boy with a history of repeated hospitalizations from birth due to severe jaundice and hyperthyroidism. At the age of 2 years, he suffered from a proximal left femoral fracture. During the follow‐up, liver function tests were abnormal. Considering the clinical and paraclinical findings, the patient was diagnosed with McCune–Albright syndrome.

In McCune–Albright syndrome, functional mutations in the GNAS can cause a wide range of clinical phenotypes. Considering the previously reported cases and the mentioned case, neonatal jaundice can be an early sign of this syndrome.

Neonatal cholestasis can be the first symptom of McCune–Albright syndrome: A case report

BACKGROUND

McCune–Albright syndrome (MAS) is caused by postzygotic somatic mutations of the GNAS gene. It is characterized by the clinical triad of fibrous dysplasia, café-au-lait skin spots, and endocrinological dysfunction. Myriad complications in MAS, including hepatobiliary manifestations, are also reported.

CASE SUMMARY

This is a case of a 4-year-old boy who presented with MAS with neonatal cholestasis. He was suspected to have Alagille syndrome due to neonatal cholestasis with intrahepatic bile duct paucity in liver biopsy, peripheral pulmonary artery stenosis, and renal tubular dysfunction. By the age of 2 years, his cholestatic liver injury gradually improved, but he had repeated left femoral fractures. He did not exhibit endocrinological abnormality or café-au-lait skin spots. However, MAS was suspected due to fibrous dysplasia at the age of 4 years. No mutation was identified in the GNAS gene in the DNA isolated from the peripheral blood, but an activating point mutation (c.601C>T, p.Arg201Cys) was observed in the DNA extracted from the affected bone tissue and that extracted from the formalin-fixed paraffin-embedded liver tissue, which was obtained at the age of 1 mo.

CONCLUSION

MAS should be considered as a differential diagnosis for transient cholestasis in infancy.

A Novel GNAS Mutation Causing Isolated Infantile Cushing's Syndrome

Infantile Cushing's syndrome is potentially found as part of McCune-Albright syndrome (MAS) which is caused by postzygotic somatic mutations of the GNAS gene. MAS is typically characterized by a triad of polyostotic fibrous dysplasia, café-au-lait skin pigmentation, and precocious puberty or other endocrine hyperfunction. Here, we describe a 2-month-old female infant with features of Cushing's syndrome without café au lait spots, polyostotic fibrous dysplasia, and clinical evidence of other endocrine hyperfunction. Investigations demonstrated adrenocorticotropic hormone-independent Cushing's syndrome with bilateral adrenal gland enlargement. Whole-exome sequencing of leukocytes identified a de novo heterozygous novel missense mutation (c.521G>A, p.Cys174Tyr) in the GNAS gene. The patient experienced clinical improvement of Cushing's syndrome during ketoconazole treatment. Her clinical course was complicated by Pneumocystis jiroveci pneumonia. She also had shortened activated partial thromboplastin time indicating a hypercoagulable state and resulting in pulmonary embolism. She eventually manifested gonadotropin-independent precocious puberty at the age of 13 months after ketoco-nazole was discontinued. This patient demonstrated that Cushing syndrome can be the presenting sign of MAS in infancy. A high index of suspicion followed by genetic analysis is essential in order to establish a diagnosis.

Neonatal Cholestasis Over Time: Changes in Epidemiology and Outcome in a Cohort of 154 Patients From a Portuguese Tertiary Center

Introduction: In the last two decades there have been advances in the diagnosis and management of neonatal cholestasis, which may have changed its epidemiology, diagnostic accuracy, outcomes, and survival. Our goal was to characterize these changes over time in our setting. Methods: Retrospective cohort study in a tertiary center, enrolling patients born between January 1985 and October 2019. The cohort was divided into two periods, before (A; n = 67) and after (B; n = 87) the year 2000; and in two groups, according to patient's outcome (favorable, unfavorable). Overall survival and survival with and without orthotopic liver transplant (OLT) were evaluated in the two periods (A and B) and in different subgroups of underlying entities. Results: We found that the age of cholestasis recognition decreased significantly from period A to period B [median 43 days and 22 days, respectively, (p < 0.001)]; the changes in epidemiology were relevant, with a significant decrease in alpha-1-antitrypsin deficiency (p < 0.001) and an increase in transient cholestasis (p = 0.004). A next-generation sequencing (NGS) panel available since mid-2017 was applied to 13 patients with contributory results in 7, but, so far, only in 2 patients led to conclusive diagnosis of underlying entities. The number of cases of idiopathic cholestasis did not vary significantly. Over time there was no significant change in the outcome (p = 0.116). Overall survival and survival without OLT had no significant improvement during the period of observation (in periods A and B, 86 vs. 88%, and 85 vs. 87%, respectively). However, in period B, with OLT we achieved the goal of 100% of survival rate. Conclusions: Our data suggest that transient cholestasis became a very important subset of neonatal cholestasis, requiring specific guidance. The NGS panels can provide important inputs on disease diagnosis but, if applied without strict criteria and expertise, they can open a Pandora's box due to misinterpretation. Despite all the advances in accurate diagnosis and timely management-including early recognition of cholestasis-the improvement in patient outcomes and survival were still not significant.

Hepatic Lesions Associated With McCune Albright Syndrome

McCune-Albright syndrome (MAS) results from a GNAS gene mutation. It is associated with café au lait macules, fibrous dysplasia, and several endocrinopathies to include gonadotropin-independent precocious puberty, growth hormone excess, Cushing syndrome, thyroid disease, and renal phosphate wasting. It is recognized to be a rare cause of neonatal cholestasis. We describe the hepatic outcome of 3 children with MAS referred to a single national liver unit. All presented with high gamma-glutamyl transpeptidase cholestasis and hepatitis. Cholestasis resolved by 1 year; but hepatic inflammation persisted, and 2 children developed progressive atypical focal nodular hyperplasia and 1 developed hepatoblastoma. This the first reported malignant hepatic lesion associated with MAS. MAS should be considered part of the differential diagnosis of neonatal cholestasis and affected children should be closely monitored for the development of hepatic lesions with regular liver ultrasound and alpha fetoprotein level.

Severe Neonatal Cholestasis as an Early Presentation of McCune-Albright Syndrome

McCune-Albright syndrome (MAS) is a rare genetic disorder characterized by café-au-lait macules, polyostotic fibrous dysplasia and multiple endocrinopathies. Liver involvement, although described, is a rare complication. We review the case of a child with MAS whose initial presentation was characterized by severe neonatal cholestasis. The case demonstrates a severe phenotype of persistent cholestasis in MAS requiring liver transplantation. This phenotype has been previously considered to be a more benign feature. This case highlights the importance of consideration of MAS as an uncommon but important cause of neonatal cholestasis. Early diagnosis may allow for prompt recognition and treatment of other endocrinopathies.

Neonatal McCune-Albright Syndrome: A Unique Syndromic Profile With an Unfavorable Outcome

Somatic gain‐of‐function mutations of GNAS cause a spectrum of clinical phenotypes, ranging from McCune‐Albright syndrome (MAS) to isolated disease of bone, endocrine glands, and more rarely, other organs. In MAS, a syndrome classically characterized by polyostotic fibrous dysplasia (FD), café‐au‐lait (CAL) skin spots, and precocious puberty, the heterogenity of organ involvement, age of onset, and clinical severity of the disease are thought to reflect the variable size and the random distribution of the mutated cell clone arising from the postzygotic mutation. We report a case of neonatal MAS with hypercortisolism and cholestatic hepatobiliary dysfunction in which bone changes indirectly emanating from the disease genotype, and distinct from FD, led to a fatal outcome. Pulmonary embolism of marrow and bone fragments secondary to rib fractures was the immediate cause of death. Ribs, and all other skeletal segments, were free of changes of typical FD and fractures appeared to be the result of a mild‐to‐moderate degree of osteopenia. The mutated allele was abundant in the adrenal glands and liver, but not in skin, muscle, and fractured ribs, where it could only be demonstrated using a much more sensitive PNA hybridization probe‐based FRET (Förster resonance energy transfer) technique. Histologically, bilateral adrenal hyperplasia and cholestatic disease matched the abundant disease genotype in the adrenals and liver. Based on this case and other sporadic reports, it appears that gain‐of‐function mutations of GNAS underlie a unique syndromic profile in neonates characterized by CAL skin spots, hypercortisolism, hyperthyroidism, hepatic and cardiac dysfunction, and an absence (or latency) of FD, often with a lethal outcome. Taken together, our and previous cases highlight the phenotypic severity and the diagnostic and therapeutic challenges of MAS in neonates. Furthermore, our case specifically points out how secondary bone changes, unrelated to the direct impact of the mutation, may contribute to the unfavorable outcome of very early‐onset MAS. © 2018 The Authors JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Neonatal McCune-Albright syndrome with survival beyond two years

McCune-Albright syndrome (MAS) is a rare disease resulting from a somatic, mosaic mutation of GNAS1 encoding the G_s α subunit of the G-protein coupled membrane receptor responsible for multiple hormonal signaling cascades. We present a patient with neonatal MAS who initially presented with neonatal diabetes and concern for congenital cardiac disease, and subsequently was found to have significant ACTH-independent neonatal Cushing syndrome. Her course included multi-system organ involvement, although she initially did not have obvious findings consistent with the MAS classic triad of café-au-lait macules, fibrous dysplasia, or peripheral precocious puberty. After medical and surgical treatment, she remains the only reported survivor of neonatal MAS. This clinical report alerts clinicians to the possibility of this disease in neonates with non-classical endocrine and non-endocrine manifestations of MAS, and demonstrates that this very early presentation is potentially survivable. © 2016 Wiley Periodicals, Inc.

Neonatal McCune-Albright syndrome with systemic involvement: a case report

INTRODUCTION

McCune-Albright syndrome is a rare sporadic disease characterized by fibrous bone dysplasia, café-au-lait skin spots and variable hyperfunctional endocrinopathies. McCune-Albright syndrome is caused by somatic postzygotic activating mutations in the GNAS gene that produce a broad spectrum of effects.

CASE PRESENTATION

We report a case of McCune-Albright syndrome with multi-organ manifestations in the neonatal period. A newborn preterm black girl was referred to our Neonatal Intensive Care Unit at the age of 17 days for suspected extrahepatic cholestasis. On clinical examination she presented failure to thrive, jaundice, hypertension, marked hypotonia and café-au-lait spots on her back and lower limbs. An abdominal ultrasound excluded extrahepatic causes of cholestasis but revealed bilateral serpiginous adrenal hyperplasia. These clinical findings suggested a diagnosis of McCune-Albright syndrome with multi-organ involvement. Laboratory data confirmed adrenocorticotropic hormone-independent Cushing's syndrome, hyperthyroidism, cholestasis and elevated transaminases. Ventricular hypertrophy was demonstrated by echocardiography. The baby girl underwent medical treatment of Cushing's syndrome with metyrapone which was followed by a rapid recovery. A mosaic activating GNAS gene mutation was found on DNA extracted from a buccal swab sample. However, she died at 4 months due to a respiratory infection.

CONCLUSION

In the neonatal period the diagnosis of McCune-Albright syndrome depends on having a high index of suspicion and café-au-lait spots may be the clue for the diagnosis.

Carney complex and McCune Albright syndrome: an overview of clinical manifestations and human molecular genetics

Endocrine neoplasia syndromes feature a wide spectrum of benign and malignant tumors of endocrine and non-endocrine organs associated with other clinical manifestations. This study outlines the main clinical features, genetic basis, and molecular mechanisms behind two multiple endocrine neoplasia syndromes that share quite a bit of similarities, but one can be inherited whereas the other is always sporadic, Carney complex (CNC) and McCune-Albright (MAS), respectively. Spotty skin pigmentation, cardiac and other myxomas, and different types of endocrine tumors and other characterize Carney complex, which is caused largely by inactivating Protein kinase A, regulatory subunit, type I, Alpha (PRKAR1A) gene mutations. The main features of McCune-Albright are fibrous dysplasia of bone (FD), café-au-lait macules and precocious puberty; the disease is caused by activating mutations in the Guanine Nucleotide-binding protein, Alpha-stimulating activity polypeptide (GNAS) gene which are always somatic. We review the clinical manifestations of the two syndromes and provide an update on their molecular genetics.

Hepato-pancreato-biliary lesions are present in both Carney complex and McCune Albright syndrome: comments on P. Salpea and C. Stratakis

One of the key messages of recent Salpea and Stratakis work is to underline the clinical similarities shared by these syndromes that could be explained by a defect in the same signaling pathway, i.e. activation of the cAMP pathway. That being said, we would like to emphasize that hepatopancreato-biliary lesions are one additional feature shared both by Carney complex and McCune Albright syndrome.

Hepatobiliary and Pancreatic neoplasms in patients with McCune-Albright syndrome

BACKGROUND

McCune-Albright syndrome (MAS), which includes polycystic fibrous dysplasia, precocious puberty, and café au lait spots, is a rare disorder caused by somatic activating mutations of the GNAS gene. GNAS mutations have also been implicated in various sporadic tumors, including hepatobiliary and pancreatic neoplasms.

AIM

The aim of this study was to assess the prevalence of hepatobiliary and pancreatic neoplasms in patients with McCune-Albright syndrome.

PATIENTS AND METHODS

Nineteen patients diagnosed between 1995 and 2012 with MAS in a tertiary referral center for rare growth disorders were screened with dedicated gadolinium-enhanced magnetic resonance imaging for hepatobiliary and pancreatic neoplasms between June 2011 and December 2012.

RESULTS

Six (32%) of the 19 screened patients were found to have hepatic, pancreatic, or biliary lesions, excluding liver hemangiomas, liver cysts, and focal nodular hyperplasia. This includes pancreatic ductal lesions observed in 4 patients, including numerous branch-duct intraductal papillary mucinous neoplasms in 3 patients. Biliary lesions were observed in 1 patient, with a large choledochal cyst also involving the left biliary branch. Finally, multiple inflammatory/telangiectatic hepatic adenomas were observed in 2 patients, including 1 with proven somatic GNAS mutation.

CONCLUSION

We describe the first observation of syndromic intraductal papillary mucinous neoplasms and the new association between MAS and pancreatic neoplasms, namely intraductal papillary mucinous neoplasms of the pancreas but also rare hepatobiliary neoplasms including liver adenomas and choledochal cysts. These findings strongly suggest that somatic activating GNAS mutations, possibly through cAMP pathway disorders, are involved in the tumorigenesis of hepatobiliary and pancreatic tissues originating from the foregut endoderm and have led us to use a routine screening by dedicated magnetic resonance imaging including both pancreatobiliary and liver sequences in patients with MAS.

Spinal polyostotic fibrous dysplasia in two adults: Does only biopsy unravel the mystery?

Polyostotic fibrous dysplasia is a rare non-inheritable genetic disease due to mutation in GNAS gene. Here we present two adults who were accidentally detected lytic lesions in spine and after extensive evaluation for malignancies; was diagnosed on biopsy. Current concept of the disease and management is discussed.

McCune-Albright syndrome and the extraskeletal manifestations of fibrous dysplasia

Fibrous dysplasia (FD) is sometimes accompanied by extraskeletal manifestations that can include any combination of café-au-lait macules, hyperfunctioning endocrinopathies, such as gonadotropin-independent precocious puberty, hyperthyroidism, growth hormone excess, FGF23-mediated renal phosphate wasting, and/or Cushing syndrome, as well as other less common features. The combination of any of these findings, with or without FD, is known as McCune-Albright syndrome (MAS). The broad spectrum of involved tissues and the unpredictable combination of findings owe to the fact that molecular defect is due to dominant activating mutations in the widely expressed signaling protein, Gsα, and the fact these mutations arises sporadically, often times early in development, prior to gastrulation, and can distribute across many or few tissues.The complexity can be mastered by a systematic screening of potentially involved tissues and cognizance that the pattern of involved tissues is established, to some degree, in utero. Thorough testing allows the clinician to establish, often times at presentation, the full extent of the disease, and importantly as well what tissues are unaffected. Treatment and follow-up can then be focused on affected systems and a meaningful prognosis can be offered to the patient and family. The authors outline screening and treatment strategies that allow for effective management of the extraskeletal manifestations of FD.

Cushing syndrome in the McCune-Albright syndrome

CONTEXT

Cushing syndrome (CS) is a rare but potentially fatal feature of McCune-Albright syndrome (MAS). Optimal management, prognostic features, and long-term follow-up of this disorder have not been described.

SETTING

The study was conducted at an academic tertiary care center.

PATIENTS

A total of 112 patients participating in a natural history study at the National Institutes of Health (NIH) were evaluated, and 21 published cases were reviewed.

INTERVENTIONS

Subjects received observation, medical management, or bilateral adrenalectomy.

MAIN OUTCOME MEASURES

We measured prevalence, prognostic factors, and natural history.

RESULTS

The prevalence of CS among NIH patients was 7.1%. The median age at diagnosis was 3 months. Clinical features included "Cushingoid facies" (66.7%), failure to thrive (60.0%), low birth weight (50.0%), liver disease (36.7%), and heart disease (26.7%). Six patients (20.0%) died, four after adrenalectomy. Death was more likely in patients with comorbid heart disease (odds ratio, 13.3; P < 0.05). Of 23 survivors, 13 underwent adrenalectomy, and 10 exhibited spontaneous resolution. Two patients with spontaneous resolution who were tested later in life (3 and 15 yr after resolution) continued to have low-level, autonomous adrenal function with biochemical adrenal insufficiency. Compared to MAS patients without CS, patients with CS were more likely to have a cognitive/developmental disorder (44.4 vs. 4.8%; P < 0.001; odds ratio, 8.8).

CONCLUSIONS

Comorbid heart and liver disease were poor prognostic markers and may indicate the need for prompt adrenalectomy. The high incidence of cognitive disorders indicates a need for close developmental follow-up and parental counseling. Patients with spontaneous resolution of CS may develop adrenal insufficiency, and they require long-term monitoring.

McCune-Albright syndrome

McCune-Albright syndrome (MAS) is classically defined by the clinical triad of fibrous dysplasia of bone (FD), café-au-lait skin spots, and precocious puberty (PP). It is a rare disease with estimated prevalence between 1/100,000 and 1/1,000,000. FD can involve a single or multiple skeletal sites and presents with a limp and/or pain, and, occasionally, a pathologic fracture. Scoliosis is common and may be progressive. In addition to PP (vaginal bleeding or spotting and development of breast tissue in girls, testicular and penile enlargement and precocious sexual behavior in boys), other hyperfunctioning endocrinopathies may be involved including hyperthyroidism, growth hormone excess, Cushing syndrome, and renal phosphate wasting. Café-au-lait spots usually appear in the neonatal period, but it is most often PP or FD that brings the child to medical attention. Renal involvement is seen in approximately 50% of the patients with MAS. The disease results from somatic mutations of the GNAS gene, specifically mutations in the cAMP regulating protein, G_s alpha. The extent of the disease is determined by the proliferation, migration and survival of the cell in which the mutation spontaneously occurs during embryonic development. Diagnosis of MAS is usually established on clinical grounds. Plain radiographs are often sufficient to make the diagnosis of FD and biopsy of FD lesions can confirm the diagnosis. The evaluation of patients with MAS should be guided by knowledge of the spectrum of tissues that may be involved, with specific testing for each. Genetic testing is possible, but is not routinely available. Genetic counseling, however, should be offered. Differential diagnoses include neurofibromatosis, osteofibrous dysplasia, non-ossifying fibromas, idiopathic central precocious puberty, and ovarian neoplasm. Treatment is dictated by the tissues affected, and the extent to which they are affected. Generally, some form of surgical intervention is recommended. Bisphosphonates are frequently used in the treatment of FD. Strengthening exercises are recommended to help maintaining the musculature around the FD bone and minimize the risk for fracture. Treatment of all endocrinopathies is required. Malignancies associated with MAS are distinctly rare occurrences. Malignant transformation of FD lesions occurs in probably less than 1% of the cases of MAS.

G(s)alpha mutations in fibrous dysplasia and McCune-Albright syndrome

Fibrous dysplasia (FD) is a focal bone lesion composed of immature mesenchymal osteoblastic precursor cells. Some FD patients also have hyperpigmented skin lesions (café-au-lait spots), gonadotropin-independent sexual precocity, and/or other endocrine and nonendocrine manifestations (McCune-Albright syndrome [MAS]). MAS results from somatic mutations occurring during early development, resulting in a widespread mosaic of normal and mutant-bearing cells, which predicts that the clinical presentation of each patient is determined by the extent and distribution of abnormal cells. These mutations encode constitutively active forms of G(s)alpha, the ubiquitously expressed G protein alpha-subunit that couples hormone receptors to intracellular cAMP generation. These mutations lead to substitution of amino acid residues that are critical for the intrinsic GTPase activity that is normally required to deactivate the G protein. This leads to prolonged activation of G(s)alpha and its downstream effectors even with minimal receptor activation. This explains why MAS patients have stimulation of multiple peripheral endocrine glands in the absence of circulating stimulatory pituitary hormones and increased skin pigment, which is normally induced by melanocyte-stimulating hormone through G(s)alpha/cAMP. Similar mutations are also present in 40% of pituitary tumors in acromegaly patients and less commonly in other endocrine tumors. FD results from increased cAMP in bone marrow stromal cells, leading to increased proliferation and abnormal differentiation. Parental origin of the mutated allele may also affect the clinical presentation, because G(s)alpha is imprinted and expressed only from the maternal allele in some tissues (e.g., pituitary somatotrophs).

Fibrous dysplasia as a stem cell disease

At a time when significant attention is devoted worldwide to stem cells as a potential tool for curing incurable diseases, fibrous dysplasia of bone (FD) provides a paradigm for stem cell diseases. Consideration of the time and mechanism of the causative mutations and of nature of the pluripotent cells that mutate in early embryonic development indicates that, as a disease of the entire organism, FD can be seen as a disease of pluripotent embryonic cells. As a disease of bone as an organ, in turn, FD can be seen as a disease of postnatal skeletal stem cells, which give rise to dysfunctional osteoblasts. Recognizing FD as a stem cell disease provides a novel conceptual angle and a way to generate appropriate models of the disease, which will continue to provide further insight into its natural history and pathogenesis. In addition, skeletal stem cells may represent a tool for innovative treatments. These can be conceived as directed to alter the in vivo behavior of mutated stem cells, to replace mutated cells through local transplantation, or to correct the genetic defect in the stem cells themselves. In vitro and in vivo models are currently being generated that will permit exploration of these avenues in depth.

McCune-Albright syndrome: clinical picture and natural history in children and adolescents

The classical triad of McCune-Albright syndrome (MAS) consists of polyostotic fibrous dysplasia (FD), skin hyperpigmentation (café-au-lait spots), and endocrine dysfunction, frequently seen in females as precocious puberty. Patients with MAS display mosaicism of activating somatic mutations of the alpha-subunit of Gs. Thus, the clinical presentation of each individual is dependent on the particular distribution of affected cells, causing a broad spectrum of endocrine and non-endocrine manifestations. Typical endocrinopathies are precocious puberty, hyperthyroidism, growth hormone excess, hyperprolactemia, and hypercortisolism. The onset of these manifestations is usually during infancy and childhood. Since specific treatment is required, the prognosis depends on the severity of each individual endocrine manifestation. Additionally, there are non-endocrine manifestations, such as fibrous dysplasia of bone (FD), renal phosphate wasting, and skin hyperpigmentation, i.e. café-au-lait spots. FD, mostly polyostotic, causes fractures needing surgical and orthopedic treatment. Since previous studies have suggested the overall prognosis of patients with McCune-Albright syndrome to be non-fatal, recent data have drawn our attention to non-endocrine affections, including hepatobiliary dysfunction and cardiac disease, which are probably an important risk factor for early death. In summary, the clinical picture in MAS is related to its mosaic nature, i.e. any cell, tissue and organ in any site of the body could be affected to varying degrees, ranging from one or two mild clinical signs with excellent long-term prognosis to a severe life-threatening multiorgan disease.

A case of McCune-Albright syndrome associated with Gs alpha mutation in the bone tissue

The syndrome of McCune-Albright syndrome (MAS) is clasically defined as a triad presentation with the findings of polyostotic fibrous dysplasia, café-au-lait spots, and sexual precocity. However, not all patients present with complete symptoms. A 52-year-old man was diagnosed as having a variant of McCune-Albright syndrome with the following findings: polyostotic fibrous dysplasia, acromegaly due to pituitary tumor and subclinical hyperthyroidism due to toxic multinodular goiter. Sexual precocity and café-au-lait spots were not noted. Acromegaly was confirmed by laboratory examination (IGF-1, glucose suppression test and TRH stimulation test). Long acting somatostatin analogue was used as treatment. Although the pituitary tumor could not be removed due to technical problems, mass lesions on the cranium were removed subtotally. Histopathological evaluation demonstrated that the lesion complied with fibrous dysplasia. Genomic DNAs were isolated from the craniofacial bones and peripheral leucocytes of the patient. After amplifying the related regions, Gs alpha (Gs alpha) gene was analysed by automatic DNA sequence analysis. An activating mutation of the Gs alpha gene (Arg 201 Cys) was found in the genomic DNA isolated from the bone tissue of the patient, but not in the genomic DNA isolated from the blood. We described a case of MAS associated with Gs alpha mutation in the bone tissue, presenting with polyostotic fibrous dysplasia, subclinical hyperthyroidism and acromegaly.

[Endocrine tumors associated to protein Gsalpha/Gi2alpha mutations]

Many oncogenic mutations promote tumor growth by inducing autonomous activity of proteins that normally transmit proliferative signal initiated by extracellular factors. G proteins are a family of guanine nucleotide binding proteins, which are structurally homologous and widely distributed in eukaryotic cells. They are composed of three different subunits (alpha, beta e gamma). The alpha subunit, which contains the guanine nucleotide-binding site, is unique to each G protein. The G proteins couple an array of seven transmembrane receptors at the cell surface with a variety of intracellular effectors, which produce second messenger molecules. A subset of endocrine tumors, such as GH- or ACTH-secreting pituitary adenomas, functioning thyroid adenomas, adrenocortical and gonadal tumors were associated with somatic activating mutations in the highly conserved codons of the Gs (Arg201 and Gln227) and Gi (Arg179 and Gln205) proteins. These findings indicated that the G proteins play a role as oncogenes, contributing with the human endocrine tumorigenesis.

Paget's disease and fibrous dysplasia

Paget's disease and fibrous dysplasia are benign disorders that can involve the temporal bone and skull base. They commonly lead to otolaryngologic symptoms such as impingement of cranial nerves or the orbit or blockage of the external auditory canal or paranasal sinuses, although they can often be a challenge to diagnose because of their insidious presentation. Their benign nature and common presentation within the difficult-to-access confines of the skull base should lead the clinician to exercise caution in their treatment, reserving surgical intervention for either diagnosis or the relief of symptoms. As a better understanding of the etiology of these conditions develops and new pharmacotherapeutic agents are tested, it is likely that physicians will be able to turn to medical rather than surgical techniques to treat these disorders.

McCune-Albright syndrome: a case report and review of the literature

Nasal obstruction is one of the most common symptoms pediatric patients present to their physicians with. Usually this symptom is caused by allergic rhinitis or an upper respiratory infection, however, many conditions present with nasal obstruction. We present a 14-year-old patient with a rare cause of nasal obstruction, turbinate enlargement due to fibrous dysplasia, as diagnosed by CT scan and histopathologic analysis. Additionally, clinical history revealed precocious puberty, and a dermatologic exam revealed a café au lait macule, consistent with the McCune-Albright syndrome. This case illustrates the need to formulate a broad differential diagnosis and also consider the overall patient, not just the nasal cavity. The clinical presentation, diagnostic evaluation, long-term management plan and relevant literature are discussed.

A novel, complex heterozygous mutation within Gsalpha gene in patient with McCune-Albright syndrome

McCune-Albright syndrome (MAS) is caused by embryonic somatic mutations leading to the substitution of His or Cys for Arg at amino acid 201 of the alpha-subunit of the signal transduction protein Gs (Gsalpha). The mutations have been found in many affected tissues of patients with MAS. Recently, a new missense mutation was detected in a patient with MAS, leading to the substitution of glycine for arginine at amino acid 201 of the Gsalpha gene, whereas no mutations have been reported at other sites in this gene. In the present study, we identified the activating mutations in the gene encoding Gsalpha protein in the osseous lesions of fibrous dysplasia and peripheral blood leukocyte in a 17-yr-old male patient with MAS. In addition, a heterozygous mutation encoding substitution of Arg201 of Gsalpha with His was found. Interestingly, we also found the other two types of mutations within the Gsalpha gene in the patient's affected osseous tissue. One is a combination mutation in the same allele at codons 209 and 210 of the Gsalpha gene, and the other the missense mutation at codon 235.

Gs(alpha) mutations and imprinting defects in human disease

Gs is the ubiquitously expressed heterotrimeric G protein that couples receptors to the effector enzyme adenylyl cyclase and is required for receptor-stimulated intracellular cAMP generation. Activated receptors promote the exchange of GTP for GDP on the Gs alpha-subunit (Gs(alpha)), resulting in Gs activation; an intrinsic GTPase activity of Gs(alpha) deactivates Gs by hydrolyzing bound GTP to GDP. Mutations of Gs(alpha) residues involved in the GTPase reaction that lead to constitutive activation are present in endocrine tumors, fibrous dysplasia of bone, and McCune-Albright syndrome. Heterozygous loss-of-function mutations lead to Albright hereditary osteodystrophy (AHO), a disease characterized by short stature, obesity, and skeletal defects, and are sometimes associated with progressive osseous heteroplasia. Maternal transmission of Gs(alpha) mutations leads to AHO plus resistance to several hormones (e.g., parathyroid hormone) that activate Gs in their target tissues (pseudohypoparathyroidism type IA), while paternal transmission leads only to the AHO phenotype (pseudopseudohypoparathyroidism). Studies in both mice and humans demonstrate that Gs(alpha) is imprinted in a tissue-specific manner, being expressed primarily from the maternal allele in some tissues and biallelically expressed in most other tissues. This likely explains why multihormone resistance occurs only when Gs(alpha) mutations are inherited maternally. The Gs(alpha) gene GNAS1 has at least four alternative promoters and first exons, leading to the production of alternative gene products including Gs(alpha), XL alphas (a novel Gs(alpha) isoform expressed only from the paternal allele), and NESP55 (a chromogranin-like protein expressed only from the maternal allele). The fourth alternative promoter and first exon (exon 1A) located just upstream of the Gs(alpha) promoter is normally methylated on the maternal allele and is transcriptionally active on the paternal allele. In patients with parathyroid hormone resistance but without AHO (pseudohypoparathyroidism type IB), the exon 1A promoter region is unmethylated and transcriptionally active on both alleles. This GNAS1 imprinting defect is predicted to decrease Gs(alpha) expression in tissues where Gs(alpha) is normally imprinted and therefore to lead to renal parathyroid hormone resistance.

Common diagnostic problems in pediatric liver pathology

The role of the pathologist in dealing with common problems of liver disease in children is likely to change dramatically as the molecular genetic revolution progresses. For example, microchip arrays for genes involved in bile salt synthesis and transport will pinpoint the specific mutations responsible for infantile cholestasis and similar methods will sort out infectious agents of acute and chronic hepatitis. But even as biochemistry, microbiology, and immunology laboratories already provide essential diagnostic information in such settings, informed histopathologic interpretation will continue to guide investigations of etiology and therapeutics and will remain an important medical necessity [95,96,100,102,104].

Endocrine manifestations of stimulatory G protein alpha-subunit mutations and the role of genomic imprinting

The heterotrimeric G protein G(s) couples hormone receptors (as well as other receptors) to the effector enzyme adenylyl cyclase and is therefore required for hormone-stimulated intracellular cAMP generation. Receptors activate G(s) by promoting exchange of GTP for GDP on the G(s) alpha-subunit (G(s)alpha) while an intrinsic GTPase activity of G(s)alpha that hydrolyzes bound GTP to GDP leads to deactivation. Mutations of specific G(s)alpha residues (Arg(201) or Gln(227)) that are critical for the GTPase reaction lead to constitutive activation of G(s)-coupled signaling pathways, and such somatic mutations are found in endocrine tumors, fibrous dysplasia of bone, and the McCune-Albright syndrome. Conversely, heterozygous loss-of-function mutations may lead to Albright hereditary osteodystrophy (AHO), a disease characterized by short stature, obesity, brachydactyly, sc ossifications, and mental deficits. Similar mutations are also associated with progressive osseous heteroplasia. Interestingly, paternal transmission of GNAS1 mutations leads to the AHO phenotype alone (pseudopseudohypoparathyroidism), while maternal transmission leads to AHO plus resistance to several hormones (e.g., PTH, TSH) that activate G(s) in their target tissues (pseudohypoparathyroidism type IA). Studies in G(s)alpha knockout mice demonstrate that G(s)alpha is imprinted in a tissue-specific manner, being expressed primarily from the maternal allele in some tissues (e.g., renal proximal tubule, the major site of renal PTH action), while being biallelically expressed in most other tissues. Disrupting mutations in the maternal allele lead to loss of G(s)alpha expression in proximal tubules and therefore loss of PTH action in the kidney, while mutations in the paternal allele have little effect on G(s)alpha expression or PTH action. G(s)alpha has recently been shown to be also imprinted in human pituitary glands. The G(s)alpha gene GNAS1 (as well as its murine ortholog Gnas) has at least four alternative promoters and first exons, leading to the production of alternative gene products including G(s)alpha, XLalphas (a novel G(s)alpha isoform that is expressed only from the paternal allele), and NESP55 (a chromogranin-like protein that is expressed only from the maternal allele). A fourth alternative promoter and first exon (exon 1A) located approximately 2.5 kb upstream of the G(s)alpha promoter is normally methylated on the maternal allele and transcriptionally active on the paternal allele. In patients with isolated renal resistance to PTH (pseudohypoparathyroidism type IB), the exon 1A promoter region has a paternal-specific imprinting pattern on both alleles (unmethylated, transcriptionally active), suggesting that this region is critical for the tissue-specific imprinting of G(s)alpha. The GNAS1 imprinting defect in pseudohypoparathyroidism type IB is predicted to decrease G(s)alpha expression in renal proximal tubules. Studies in G(s)alpha knockout mice also demonstrate that this gene is critical in the regulation of lipid and glucose metabolism.

Cholestatic syndromes

New insights into the regulation of hepatobiliary transport proteins have provided the basis for a better understanding of the pathogenesis of cholestatic liver diseases. Mutations of transporter genes can cause hereditary cholestatic syndromes, the study of which has shed much light on the basic mechanisms of bile secretion and cholestasis. Important new studies have been published about the pathogenesis, clinical features, and treatment of primary biliary cirrhosis, primary sclerosing cholangitis, cholestasis of pregnancy, total parenteral nutrition-induced cholestasis, and drug-induced cholestasis.