Diagnosis and Treatment > Investigation > Genetic analysis
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Summary
At least 40% of phaeochromocytomas and paraganglioma’s (PPGLs) are associated with an underlying genetic mutation. The understanding of the genetic landscape of these tumours has rapidly evolved, with 18 associated genes now identified. Among these, mutations in the subunits of succinate dehydrogenase complex (SDH) are the most common, causing around half of familial PPGL cases. Occurrence of PPGLs in carriers of SDHB, SDHC and SDHD subunit mutations has been long reported, but it is only recently that variants in the SDHA subunit have been linked to PPGL formation. Previously documented cases have, to our knowledge, only been found in isolated cases where pathogenic SDHA variants were identified retrospectively. We report the case of an asymptomatic suspected carotid body tumour found during surveillance screening in a 72-year-old female who is a known carrier of a germline SDHA pathogenic variant. To our knowledge, this is the first screen that detected PPGL found in a previously identified SDHA pathogenic variant carrier, during surveillance imaging. This finding supports the use of cascade genetic testing and surveillance screening in all carriers of a pathogenic SDHA variant.
Learning points:
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SDH mutations are important causes of PPGL disease.
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SDHA is much rarer compared to SDHB and SDHD mutations.
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Pathogenicity and penetrance are yet to be fully determined in cases of SDHA-related PPGL.
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Surveillance screening should be used for SDHA PPGL cases to identify recurrence, metastasis or metachronous disease.
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Surveillance screening for SDH-related disease should be performed in identified carriers of a pathogenic SDHA variant.
Search for other papers by Yang Timothy Du in
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SA Pathology, Women’s and Children’s Hospital
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Search for other papers by Nicola K Poplawski in
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School of Medicine, University of Adelaide
Adult Genetics Unit, Royal Adelaide Hospital
Center for Cancer Biology, SA Pathology and University of South Australia Alliance, Adelaide, South Australia, Australia
Search for other papers by Sunita M C De Sousa in
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Summary
A 26-year-old man presented with a combination of permanent neonatal diabetes due to pancreatic aplasia, complex congenital heart disease, central hypogonadism and growth hormone deficiency, structural renal abnormalities with proteinuria, umbilical hernia, neurocognitive impairment and dysmorphic features. His older brother had diabetes mellitus due to pancreatic hypoplasia, complex congenital heart disease, hypospadias and umbilical hernia. Their father had an atrial septal defect, umbilical hernia and diabetes mellitus diagnosed incidentally in adulthood on employment screening. The proband’s paternal grandmother had a congenital heart defect. Genetic testing of the proband revealed a novel heterozygous missense variant (Chr18:g.19761441T>C, c.1330T>C, p.Cys444Arg) in exon 4 of GATA6, which is class 5 (pathogenic) using American College of Medical Genetics and Genomics guidelines and is likely to account for his multisystem disorder. The same variant was detected in his brother and father, but not his paternal grandmother. This novel variant of GATA6 likely occurred de novo in the father with autosomal dominant inheritance in the proband and his brother. The case is exceptional as very few families with monogenic diabetes due to GATA6 mutations have been reported to date and we describe a new link between GATA6 and renal pathology.
Learning points:
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Monogenic diabetes should be suspected in patients presenting with syndromic features, multisystem congenital disease, neonatal-onset diabetes and/or a suggestive family history.
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Recognition and identification of genetic diabetes may improve patient understanding and empowerment and allow for better tailored management.
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Identification of a genetic disorder may have important implications for family planning.
Eastern Health Clinical School, Monash University, Victoria, Australia
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Search for other papers by Rosemary Wong in
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Medical Imaging, Eastern Health, Box Hill, Victoria, Australia
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Department of Medicine and Radiology, University of Melbourne, Victoria, Australia
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Eastern Health Clinical School, Monash University, Victoria, Australia
Department of Medicine, Eastern Health, Box Hill, Victoria, Australia
Search for other papers by Christopher Gilfillan in
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Summary
Mitochondrial diseases are rare, heterogeneous conditions affecting organs dependent on high aerobic metabolism. Presenting symptoms and signs vary depending on the mutation and mutant protein load. Diabetes mellitus is the most common endocrinopathy, and recognition of these patients is important due to its impact on management and screening of family members. In particular, glycemic management differs in these patients: the use of metformin is avoided because of the risk of lactic acidosis. We describe a patient who presented with gradual weight loss and an acute presentation of hyperglycemia complicated by the superior mesenteric artery syndrome. His maternal history of diabetes and deafness and a personal history of hearing impairment led to the diagnosis of a mitochondrial disorder.
Learning points:
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The constellation of diabetes, multi-organ involvement and maternal inheritance should prompt consideration of a mitochondrial disorder.
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Mitochondrial encephalomyopathy, lactic acidosis, stroke-like episodes (MELAS) and maternally inherited diabetes and deafness (MIDD) are the most common mitochondrial diabetes disorders caused by a mutation in m.3243A>G in 80% of cases.
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Metformin should be avoided due to the risk of lactic acidosis.
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There is more rapid progression to insulin therapy and higher prevalence of diabetic complications compared to type 2 diabetes.
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Diagnosis of a mitochondrial disorder leads to family screening, education and surveillance for future complications.
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Superior mesenteric artery syndrome, an uncommon but important cause of intestinal pseudo-obstruction in cases of significant weight loss, has been reported in MELAS patients.
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Search for other papers by Márta Korbonits in
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Summary
Early-onset acromegaly causing gigantism is often associated with aryl-hydrocarbon-interacting receptor protein (AIP) mutation, especially if there is a positive family history. A15y male presented with tiredness and visual problems. He was 201 cm tall with a span of 217 cm. He had typical facial features of acromegaly, elevated IGF-1, secondary hypogonadism and a large macroadenoma. His paternal aunt had a history of acromegaly presenting at the age of 35 years. Following transsphenoidal surgery, his IGF-1 normalized and clinical symptoms improved. He was found to have a novel AIP mutation destroying the stop codon c.991T>C; p.*331R. Unexpectedly, his father and paternal aunt were negative for this mutation while his mother and older sister were unaffected carriers, suggesting that his aunt represents a phenocopy.
Learning points:
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Typical presentation for a patient with AIP mutation with excess growth and eunuchoid proportions.
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Unusual, previously not described AIP variant with loss of the stop codon.
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Phenocopy may occur in families with a disease-causing germline mutation.
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Search for other papers by Talin Arslanian in
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Summary
Isolated Growth Hormone Deficiency (IGHD) is a rare cause of short stature, treated with the standard regimen of subcutaneous synthetic growth hormone (GH). Patients typically achieve a maximum height velocity in the first year of treatment, which then tapers shortly after treatment is stopped. We report a case of a 9-year-old male who presented with short stature (<3rd percentile for age and race). Basal hormone levels showed undetectable serum IGF1. Skeletal wrist age was consistent with chronologic age. Cranial MRI revealed no masses or lesions. Provocative arginine-GH stimulation testing demonstrated a peak GH level of 1.4 ng/mL. Confirmatory genetic testing revealed a rare autosomal recessive single-nucleotide polymorphism (SNP) with mutational frequency of 2%. GH supplementation was started and pursued for 2 years, producing dramatically increased height velocity. This velocity persisted linearly through adolescence, several years after treatment had been discontinued. Final adult height was >95th percentile for age and race. In conclusion, this is a case of primary hypopituitarism with differential diagnosis of IGHD vs Idiopathic Short Stature vs Constitutional Growth Delay. This case supports two objectives: Firstly, it highlights the importance of confirmatory genetic testing in patients with suspected, though diagnostically uncertain, IGHD. Secondly, it demonstrates a novel secondary growth pattern with implications for better understanding the tremendous variability of GH treatment response.
Learning points:
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GHD is a common cause of growth retardation, and IGHD is a specific subtype of GHD in which patients present solely with short stature.
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The standard treatment for IGHD is subcutaneous synthetic GH until mid-parental height is reached, with peak height velocity attained in the 1st year of treatment in the vast majority of patients.
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Genetic testing should be strongly considered in cases of diagnostic uncertainty prior to initiating treatment.
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Future investigations of GH treatment response that stratify by gene and specific mutation will help guide treatment decisions.
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Response to treatment in patients with IGHD is variable, with some patients demonstrating little to no response, while others are ‘super-responders.’
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Search for other papers by Faisal Al-Zidgali in
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Search for other papers by Bibian N Ofoegbu in
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Summary
Wolcott–Rallison syndrome (WRS) is a rare autosomal recessive disorder due to mutations in the EIF2AK3 gene. It is characterized by permanent neonatal diabetes mellitus, skeletal dysplasia, liver impairment, neutropenia and renal dysfunction. Liver is the most commonly affected organ and liver failure is the commonest cause of death in this syndrome. The EIF2AK3 gene encodes a transmembrane protein PERK, which is important for the cellular response to endoplasmic reticulum (ER) stress. The absence of PERK activity reduces the ER’s abilities to deal with stress, leading to cell death by apoptosis. On acquiring febrile illness, affected patients suffer from liver injury, which may progress into liver failure and death. Renal involvement is less common and is mainly in the form of functional renal impairment at the advanced stage of the disease. Structural renal anomalies have not been reported in WRS. We report a 6-month-old girl who presented with neonatal diabetes on day 1 of life. Her genetic testing confirmed WRS due to missense mutation in the EIF2AK3 gene (c.2867G > A, p.Gly956Glu). Parents are first-degree cousins and both are heterozygous carriers to the mutation. 2 paternal uncles had the same mutation and died of liver disease at 1 and 14 years of age. Neither had a renal disease. She presented with hematuria during a febrile illness at the age of 5 months. Ultrasound scan showed right ectopic multicystic dysplastic kidney (MCDK). To the best of our knowledge, this is the first patient with WRS who is reported to have an MCDK disease.
Learning points:
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Neonatal diabetes should be considered in babies presenting with early hyperglycemia particularly if there is a family history.
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Genetic diagnosis in neonatal diabetes enables disease confirmation, genetic counseling and anticipation of potential complications during concomitant situations such as acute illness, trauma or major surgery.
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There is lack of phenotype–genotype correlation in Wolcott–Rallison syndrome.
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Structural kidney abnormality, in our case MCDK, can be seen in WRS.
Search for other papers by Elena Carrillo in
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Search for other papers by Cristina Lamas in
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Summary
Mutations in hepatocyte nuclear factor 1β gene (HNF1B) are responsible for a multisystemic syndrome where monogenic diabetes (classically known as MODY 5) and renal anomalies, mostly cysts, are the most characteristic findings. Urogenital malformations, altered liver function tests, hypomagnesemia or hyperuricemia and gout are also part of the syndrome. Diabetes in these patients usually requires early insulinization. We present the case of a young non-obese male patient with a personal history of renal multicystic dysplasia and a debut of diabetes during adolescence with simple hyperglycemia, negative pancreatic autoimmunity and detectable C-peptide levels. He also presented epididymal and seminal vesicle cysts, hypertransaminasemia, hyperuricemia and low magnesium levels. In the light of these facts we considered the possibility of a HNF1B mutation. The sequencing study of this gene confirmed a heterozygous mutation leading to a truncated and less functional protein. Genetic studies of his relatives were negative; consequently, it was classified as a de novo mutation. In particular, our patient maintained good control of his diabetes on oral antidiabetic agents for a long period of time. He eventually needed insulinization although oral therapy was continued alongside, allowing reduction of prandial insulin requirements. The real prevalence of mutations in HNF1B is probably underestimated owing to a wide phenotypical variability. As endocrinologists, we should consider this possibility in young non-obese diabetic patients with a history of chronic non-diabetic nephropathy, especially in the presence of some of the other characteristic manifestations.
Learning points:
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HNF1B mutations are a rare cause of monogenic diabetes, often being a part of a multisystemic syndrome.
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The combination of young-onset diabetes and genitourinary anomalies with slowly progressive nephropathy of non-diabetic origin in non-obese subjects should rise the suspicion of such occurrence. A family history may not be present.
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Once diagnosis is made, treatment of diabetes with oral agents is worth trying, since the response can be sustained for a longer period than the one usually described. Oral treatment can help postpone insulinization and, once this is necessary, can help reduce the required doses.
Search for other papers by Pradeep Vasudevan in
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Search for other papers by Corrina Powell in
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Search for other papers by Nadia Schoenmakers in
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Summary
In the absence of maternal thyroid disease or iodine deficiency, fetal goitre is rare and usually attributable to dyshormonogenesis, for which genetic ascertainment is not always undertaken in the UK. Mechanical complications include tracheal and oesophageal compression with resultant polyhydramnios, malpresentation at delivery and neonatal respiratory distress. We report an Indian kindred in which the proband (first-born son) had congenital hypothyroidism (CH) without obvious neonatal goitre. His mother’s second pregnancy was complicated by fetal hypothyroid goitre and polyhydramnios, prompting amniotic fluid drainage and intraamniotic therapy (with liothyronine, T3 and levothyroxine, T4). Sadly, intrauterine death occurred at 31 weeks. Genetic studies in the proband demonstrated compound heterozygous novel (c.5178delT, p.A1727Hfs*26) and previously described (c.7123G > A, p.G2375R) thyroglobulin (TG) mutations which are the likely cause of fetal goitre in the deceased sibling. TG mutations rarely cause fetal goitre, and management remains controversial due to the potential complications of intrauterine therapy however an amelioration in goitre size may be achieved with intraamniotic T4, and intraamniotic T3/T4 combination has achieved a favourable outcome in one case. A conservative approach, with surveillance, elective delivery and commencement of levothyroxine neonatally may also be justified, although intubation may be required post delivery for respiratory obstruction. Our observations highlight the lethality which may be associated with fetal goitre. Additionally, although this complication may recur in successive pregnancies, our case highlights the possibility of discordance for fetal goitre in siblings harbouring the same dyshormonogenesis-associated genetic mutations. Genetic ascertainment may facilitate prenatal diagnosis and assist management in familial cases.
Learning points:
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CH due to biallelic, loss-of-function TG mutations is well-described and readily treatable in childhood however mechanical complications from associated fetal goitre may include polyhydramnios, neonatal respiratory compromise and neck hyperextension with dystocia complicating delivery.
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CH due to TG mutations may manifest with variable phenotypes, even within the same kindred.
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Treatment options for hypothyroid dyshormogenic fetal goitre in a euthyroid mother include intraamniotic thyroid hormone replacement in cases with polyhydramnios or significant tracheal obstruction. Alternatively, cases may be managed conservatively with radiological surveillance, elective delivery and neonatal levothyroxine treatment, although intubation and ventilation may be required to support neonatal respiratory compromise.
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Genetic ascertainment in such kindreds may enable prenatal diagnosis and anticipatory planning for antenatal management of further affected offspring.
ANZAC Research Institute, University of Sydney, Sydney, New South Wales, Australia
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Central Clinical School, Sydney Medical School, University of Sydney, New South Wales, Australia
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Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
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Department of Paediatrics, University of Melbourne, Melbourne, Victoria, Australia
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Summary
46,XX disorders of sexual development (DSDs) occur rarely and result from disruptions of the genetic pathways underlying gonadal development and differentiation. We present a case of a young phenotypic male with 46,XX SRY-negative ovotesticular DSD resulting from a duplication upstream of SOX9 presenting with a painful testicular mass resulting from ovulation into an ovotestis. We present a literature review of ovulation in phenotypic men and discuss the role of SRY and SOX9 in testicular development, including the role of SOX9 upstream enhancer region duplication in female-to-male sex reversal.
Learning points:
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In mammals, the early gonad is bipotent and can differentiate into either a testis or an ovary. SRY is the master switch in testis determination, responsible for differentiation of the bipotent gonad into testis.
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SRY activates SOX9 gene, SOX9 as a transcription factor is the second major gene involved in male sex determination. SOX9 drives the proliferation of Sertoli cells and activates AMH/MIS repressing the ovary. SOX9 is sufficient to induce testis formation and can substitute for SRY function.
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Assessing karyotype and then determination of the presence or absence of Mullerian structures are necessary serial investigations in any case of DSD, except for mixed gonadal dysgenesis identified by karyotype alone.
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Treatment is ideal in a multidisciplinary setting with considerations to genetic (implications to family and reproductive recurrence risk), psychological aspects (sensitive individualized counseling including patient gender identity and preference), endocrinological (hormone replacement), surgical (cosmetic, prophylactic gonadectomy) fertility preservation and reproductive opportunities and metabolic health (cardiovascular and bones).
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Summary
Proteinuric renal disease is prevalent in congenital or acquired forms of generalized lipodystrophy. In contrast, an association between familial partial lipodystrophy (FPLD) and renal disease has been documented in very few cases. A 22-year-old female patient presented with impaired glucose tolerance, hyperinsulinemia, hirsutism and oligomenorrhea. On examination, there was partial loss of subcutaneous adipose tissue in the face, upper and lower limbs, bird-like facies with micrognathia and low set ears and mild acanthosis nigricans. Laboratory investigations revealed hyperandrogenism, hyperlipidemia, elevated serum creatine kinase and mild proteinuria. A clinical diagnosis of FPLD of the non-Dunnigan variety was made; genetic testing revealed a heterozygous c.1045C > T mutation in exon 6 of the LMNA gene, predicted to result in an abnormal LMNA protein (p.R349W). Electromyography and muscle biopsy were suggestive of non-specific myopathy. Treatment with metformin and later with pioglitazone was initiated. Due to worsening proteinuria, a renal biopsy was performed; histological findings were consistent with mild focal glomerular mesangioproliferative changes, and the patient was started on angiotensin-converting enzyme inhibitor therapy. This is the fourth report of FPLD associated with the c.1045C > T missense LMNA mutation and the second with co-existent proteinuric renal disease. Patients carrying this specific mutation may exhibit a phenotype that includes partial lipodystrophy, proteinuric nephropathy, cardiomyopathy and atypical myopathy.
Learning points:
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Lipodystrophy is a rare disorder characterized by the complete or partial loss of subcutaneous adipose tissue, insulin resistance, diabetes mellitus and hyperlipidemia.
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Proteinuric renal disease is a prevalent feature of generalized lipodystrophy but rare in familial partial lipodystrophy.
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Patients carrying the c.1045C > T missense LMNA mutation (p.R349W) may present with familial partial lipodystrophy, proteinuric nephropathy, cardiomyopathy and atypical myopathy.
