Genetic analysis of Carney complex: current understanding and future questions:

Possible association between Carney complex and multiple endocrine neoplasia type 1 phenotypes

Carney Complex (CNC) and Multiple Endocrine Neoplasia type 1 (MEN1) are forms of multiple endocrine neoplasia of dominant autosomal inheritance. Diagnosis of CNC occurs when two major criteria (lentiginoses, primary pigmented nodular adrenocortical disease, cardiac and cutaneous myxomas, acromegaly, testicular neoplasias, thyroid cancer) are observed and/or a major criterion associated with a supplementary criterion (affected relative, PRKAR1A gene mutation) occurs. On the other hand, diagnosis for MEN1 occurs through detection of two or more tumors located at the pituitary gland, parathyroid and/or pancreatic cells. The present case describes a 55 year-old male patient, diagnosed with acromegaly, primary hyperparathyroidism and papillary thyroid cancer, exhibiting components that meet the diagnostic criteria of both conditions described. Despite the occurrence of only one sporadic association or the acromegaly per se being responsible for the papillary cancer, new molecular mechanisms may not be ruled out.

Mutation of Prkar1a causes osteoblast neoplasia driven by dysregulation of protein kinase A

Carney complex (CNC) is an autosomal dominant neoplasia syndrome caused by inactivating mutations in PRKAR1A, the gene encoding the type 1A regulatory subunit of protein kinase A (PKA). This genetic defect induces skin pigmentation, endocrine tumors, myxomas, and schwannomas. Some patients with the complex also develop myxoid bone tumors termed osteochondromyxomas. To study the link between the PRKAR1A mutations and tumor formation, we generated a mouse model of this condition. Prkar1a(+/-) mice develop bone tumors with high frequency, although these lesions have not yet been characterized, either from human patients or from mice. Bone tumors from Prkar1a(+/-) mice were heterogeneous, including elements of myxomatous, cartilaginous, and bony differentiation that effaced the normal bone architecture. Immunohistochemical analysis identified an osteoblastic origin for the abnormal cells associated with islands of bone. To better understand these cells at the biochemical level, we isolated primary cultures of tumoral bone and compared them with cultures of bone from wild-type animals. The tumor cells exhibited the expected decrease in Prkar1a protein and exhibited increased PKA activity. At the phenotypic level, we observed that tumor cells behaved as incompletely differentiated osteoblasts and were able to form tumors in immunocompromised mice. Examination of gene expression revealed down-regulation of markers of bone differentiation and increased expression of locally acting growth factors, including members of the Wnt signaling pathway. Tumor cells exhibited enhanced growth in response to PKA-stimulating agents, suggesting that tumorigenesis in osteoblast precursor cells is driven by effects directly mediated by the dysregulation of PKA.

Clinical features, diagnosis, treatment and molecular studies in paediatric Cushing's syndrome due to primary nodular adrenocortical hyperplasia

BACKGROUND

Primary nodular adrenocortical hyperplasia (PNAH) is a well recognized, but infrequently studied cause of paediatric Cushing's syndrome (CS).

OBJECTIVE

To assess presentation, diagnosis, radiological imaging, treatment and molecular analysis of patients with childhood-onset CS due to PNAH.

PATIENTS

Four males and two females (median age 12.9 years, range 10.9-16.9 years) were studied.

RESULTS

All had growth failure (mean height SDS -1.2; range -2.5-0.0), weight gain [mean body mass index (BMI) SDS 3.5; range 2.5-4.6] and clinical virilization, while five had hypertension [mean systolic blood pressure (SBP) 130 mmHg, diastolic blood pressure (DBP) 83 mmHg]. One patient had generalized lentigines, one had a tibial chondromyxomatous cyst and two had facial freckling. One patient had a family history of primary nodular adrenocortical disease. The diagnosis of CS was based on elevation of sleeping midnight serum cortisol and urinary free cortisol excretion, and impaired suppression of cortisol on both low- and high-dose dexamethasone suppression tests (DST). All patients had undetectable plasma ACTH with absent responses of both plasma ACTH and serum cortisol to an intravenous (i.v.) corticotrophin-releasing hormone (CRH) test. Computed tomography or magnetic resonance imaging showed normal or small adrenals, with nodules in two patients. All patients underwent bilateral adrenalectomy, performed by open (n = 2) or laparoscopic surgery (n = 4) at a mean of 0.4 years (range 0.2-0.8 years) from diagnosis. Hypercortisolaemia was treated preoperatively by metyrapone alone 0.50-0.75 g/day (n = 4), metyrapone 0.75-1.50 g/day + o'p'DDD/mitotane 1-2 g/day (n = 1), or ketoconazole (n = 1). Adrenal histology showed nodular cortical hyperplasia with shrinkage of intervening cortical tissue and pigmentation, present in four patients. Molecular analysis of the type 1-alpha regulatory subunit of protein kinase A (PRKAR1A) gene revealed a novel germline mutation in one patient. Postadrenalectomy, three patients, had catch-up growth with height velocities increasing from 3.0, 3.9 and 2.5-8.9, 8.3 and 9.0 cm/years, respectively. All six are well at a follow-up (mean 4.0 years; range 0.5-10.8 years).

CONCLUSIONS

PNAH was associated with cushingoid features, virilization and hypertension with a lack of cortisol suppression on high DST, undetectable plasma ACTH and absent cortisol and ACTH responses to CRH. Adrenals were normal or small on imaging. PRKAR1A gene analysis may be helpful in the assessment of these patients.