Abstract
Introduction
Cushing syndrome is characterized by prolonged exposure to excess glucocorticoids and is broadly classified as either ACTH-dependent or ACTH-independent [1, 2]. Primary pigmented nodular adrenocortical disease (PPNAD) is a rare cause of ACTH-independent Cushing syndrome, characterized by bilateral adrenal hyperplasia with autonomous, hyperfunctioning nodules [1, 2]. Approximately 90% of PPNAD cases occur in the context of Carney complex, with isolated cases being exceedingly uncommon [1, 2].
PPNAD was first described in 1984 by Carney et al, who coined the term in a case series of 4 patients and a review of 24 previously reported cases [1]. In that series, patients presented with ACTH-independent Cushing syndrome and no radiographic evidence of adrenal tumors. All underwent bilateral adrenalectomy, with histopathology revealing bilateral pigmented nodules in otherwise small or normal-sized adrenal glands [1]. Histologically, the classic features of PPNAD include multiple small black or brown cortical nodules surrounded by an atrophic adrenal cortex—reflecting chronic ACTH suppression [1].
Clinically, PPNAD most often presents with cyclical Cushing syndrome, characterized by alternating periods of hypercortisolism and normocortisolemia [2]. This intermittent pattern poses a substantial diagnostic challenge, as biochemical confirmation requires detection of cortisol excess during active phases of the cycle.
Carney complex is a multiple neoplasia syndrome involving endocrine, cardiac, cutaneous, and neural tumors. First described by Carney et al in 1985, it is typically inherited in an autosomal dominant fashion. Approximately 70% of cases occur in familial settings, while the remaining 30% arise from de novo pathogenic variants [3, 4]. Over half of affected individuals harbor pathogenic variants in the PRKAR1A tumor suppressor gene on chromosome 17q24.2, while approximately 20% of cases are linked to alternate loci such as 2p16 [2, 4].
Diagnostic criteria for Carney complex include either 2 clinical manifestations or 1 clinical manifestation in combination with a pathogenic PRKAR1A variant or an affected first-degree relative [2]. The most common endocrine manifestation is PPNAD, reported in approximately 25% of patients with Carney complex, though this likely underestimates the true prevalence, as autopsy studies reveal histologic evidence of PPNAD in nearly all affected individuals [2].
The Endocrine Society clinical practice guidelines recommend bilateral adrenalectomy as the definitive treatment for PPNAD, effectively curing hypercortisolism but necessitating lifelong glucocorticoid and mineralocorticoid replacement therapy due to resultant adrenal insufficiency [5]. Unilateral adrenalectomy has emerged as an alternative approach, particularly in pediatric patients, with the potential to preserve endogenous adrenal function.
Herein, we present the case of a 9-year-old boy with Carney complex and cyclical Cushing syndrome due to PPNAD, successfully managed with unilateral adrenalectomy.
Case Presentation
A 4-year-old boy presented with a week-long history of facial swelling, hyperphagia, weight gain, and scrotal swelling. At presentation, his weight was 22 kg (99th percentile) and body mass index (BMI) was 18 kg/m² (96th percentile). Initial workup revealed normal 24-hour urinary free cortisol <0.0913 µg/day (SI: 274 nmol/day) with low urinary creatinine 215 mg/day (SI: 1.9 mmol/day) (normal reference range 973-2195 mg/day; SI: 8.6-19.4 mmol/day) suggesting an incomplete sample. A repeat collection produced similar results. A 1 mg dexamethasone suppression test demonstrated nonsuppressed cortisol (27.9 µg/dL; SI: 772 nmol/L), suggestive of Cushing syndrome.
Over 5 years, the patient experienced 2 to 3 episodes per year of rapid weight gain (20-50 lbs), facial flushing, abdominal distention, and mood changes. Despite persistent obesity (>97th percentile), linear growth remained normal.
Diagnostic Assessment
At age 7, midnight salivary cortisol was markedly elevated at 3.7 µg/dL (SI: 103 nmol/L) (normal reference range < 0.4 µg/dL; SI: < 11.3 nmol/L), raising suspicion for cyclical Cushing syndrome. Magnetic resonance imaging of the abdomen was negative for adrenal lesions. At age 8, during an active episode, 2 elevated salivary cortisol samples, 2.0 µg/dL (SI: 55.1 nmol/L) and 2.2 µg/dL (SI: 61.9 nmol/L) (normal reference range < 0.4 µg/dL; SI: < 11.3 nmol/L), were obtained. A high-dose dexamethasone suppression test yielded a low baseline cortisol 3.2 µg/dL (SI: 89 nmol/L) and nonsuppressed cortisol post-dexamethasone 3.0 µg/dL (SI: 83 nmol/L). Baseline ACTH was 7.7 pg/mL (SI: 1.7 pmol/L), suppressed to <3.2 pg/mL (SI: < 0.7 pmol/L) post-dexamethasone—consistent with ACTH-independent cortisol excess.
At age 9, the patient underwent the gold standard diagnostic testing for cyclical Cushing, the Liddle test. The test involves 6 days of urine collection: days 1 to 2 establish baseline urinary cortisol levels, days 3 to 4 assess response to low-dose dexamethasone, and days 5 to 6 evaluate response to high-dose dexamethasone. The patient’s cortisol increased paradoxically from 118.5 µg/day (SI: 327 nmol/day) to 402.0 µg/day (SI: 1109 nmol/day) over 6 days, consistent with PPNAD physiology. Genetic testing was performed with the following report: “A heterozygous variant, NM_002734.4(PRKAR1A):c.550-2_553delinsG, p.(Val184_Tyr185delinsAsp), was detected in exon 7 of this gene. This variant does not appear to have been reported in population (gnomAD, ESP, dbSNP) and clinical databases (ClinVar), or in the literature. The impact of this variant on RNA splicing as assessed by multiple algorithms (Alamut Suite) is: abolishment of canonical acceptor splice site. Based on the current evidence, this variant was classified as likely pathogenic, American College for Medical Genetics category 2”. Family testing revealed this to be a de novo pathogenic variant.
Further workup included echocardiogram and thyroid ultrasound, both of which were normal. During workup for scrotal swelling at initial presentation, the patient was found to have bilateral testicular masses with negative testicular cancer tumor markers: α-fetoprotein, human chorionic gonadotropin, and lactate dehydrogenase. The family declined invasive biopsy of these lesions. He was followed by pediatric urology with yearly serial ultrasound, and these were felt to be benign testicular tumors, presumed noncalcifying Sertoli cell tumors, associated with Carney complex (Fig. 1).
Ultrasound of bilateral testicular lesions. A) Left testicle. B) Right testicle.
Based on the presence of 2 major diagnostic criteria in combination with the molecular diagnosis of a likely pathogenic variant of PRKAR1A, the diagnosis of Carney complex was established.
Treatment
The patient was referred for surgical evaluation for consideration of adrenalectomy. A comprehensive discussion was conducted regarding the potential benefits and risks of unilateral vs bilateral adrenalectomy. The family was counseled that unilateral adrenalectomy might not fully resolve the hypercortisolemia and that a subsequent contralateral adrenalectomy could be necessary. In contrast, bilateral adrenalectomy would definitively address cortisol excess but result in permanent adrenal insufficiency requiring lifelong glucocorticoid and mineralocorticoid replacement. After multidisciplinary consultation with endocrinology and surgery, the decision was made to proceed with unilateral adrenalectomy.
Preoperative IV contrast-enhanced computed tomography (CT), reviewed by a physician experienced in PPNAD, demonstrated greater nodularity in the left adrenal gland compared to the right. Therefore, a laparoscopic left adrenalectomy was performed electively without intraoperative complications. The patient was discharged on postoperative day 1. At the time of surgery (age 9), his weight was 70 kg (100th percentile), and BMI was 31.6 kg/m² (99th percentile). The resected left adrenal gland was submitted for histopathologic evaluation. Gross examination revealed no overt nodularity (Fig. 2); however, microscopic analysis identified multiple pigmented cortical nodules consistent with PPNAD (Fig. 3).
Left adrenal gland gross morphology. No macroscopic nodularity appreciable.
Hematoxylin and Eosin staining on microscopy of left adrenal gland demonstrating hyperpigmented nodule.
Outcome and Follow-up
The patient was followed closely in the postoperative period and was last evaluated 11 months after adrenalectomy. He remained clinically well, with complete resolution of Cushingoid features and no evidence of recurrence. Since surgery, he had experienced significant weight loss of 11.4 kg, with a current weight of 58.6 kg and a BMI of 25 kg/m² (97th percentile).
In summary, this case describes a 9-year-old boy with ACTH-independent, cyclical Cushing syndrome secondary to PPNAD, associated with a de novo likely pathogenic variant in the PRKAR1A gene, consistent with Carney complex. Histopathologic analysis of the resected adrenal gland confirmed the diagnosis of PPNAD. At nearly 1 year post-unilateral adrenalectomy, the patient remains asymptomatic with no biochemical or clinical signs of disease recurrence.
Discussion
Diagnosis of cyclical Cushing is challenging due to the cyclical nature of the disease and the challenges with current available testing modalities. Late-night salivary cortisol testing was a more reliable screening tool in this case as the 24-hour urinary cortisol were affected by inaccurate collection. The cyclical nature of the disease, coupled with the necessity for appropriately timed testing, contributed to a prolonged interval before definitive diagnosis and treatment. Additionally, initial imaging was interpreted as normal, and it was only upon review by a clinician with expertise in PPNAD that subtle adrenal nodularity was identified on CT. Ultimately, the Liddle test and genetic testing were the highest yield for confirmation of disease. This test measures the suppressibility of endogenous cortisol following exogenous dexamethasone administration. In patients with PPNAD, a paradoxical increase in cortisol excretion may occur, attributed to glucocorticoid receptor–mediated activation of protein kinase A catalytic subunits [6]. The likely pathogenic variant found in this case is a novel, previously unreported, variant in the PRKAR1A gene. This rare variant impact both the canonical acceptor splice site in intron 6 as well as results in an in-frame protein change in exon 7 (Val184_Tyr185delinsAsp).
The treatment of PPNAD in the context of Carney complex is typically with bilateral adrenalectomy, as per Endocrine Society guidelines [5]. The drawback of bilateral adrenalectomy is the resultant adrenal insufficiency resulting in lifelong adrenal replacement. Unilateral adrenalectomy is an attractive option for the treatment of PPNAD given the ability to avoid adrenal insufficiency brought upon by bilateral adrenalectomy. Case reports and case series in adult patients have demonstrated variable success in unilateral treatment. In a case series of 17 patients with classic cyclical Cushing, 3 patients had recurrence of Cushing syndrome after unilateral adrenalectomy and were cured with contralateral adrenalectomy [7]. One patient had subtotal (<90%) left adrenalectomy and did not have recurrence with 66 years of follow-up [7].
A case series by Xu et al 2013 described 12 out of 13 patients with PPNAD successfully cured with unilateral adrenalectomy at median 47 months follow-up [8]. The side of adrenalectomy was selected based on CT/magnetic resonance imaging in 3 patients and adrenal iodine131-norcholesterol scintigraphy in the remaining. At our center, the iodine131-norcholesterol scintigraphy was not available so CT was the chosen imaging modality.
Ultimately, the efficacy and morbidity of unilateral adrenalectomy remains unclear. Furthermore, due to the rarity of PPNAD, the criteria for selection of patients who are candidates for unliteral adrenalectomy is challenging to establish. This case reports adds to the existing literature the clinical characteristics of one patient treated successfully by unilateral adrenalectomy.
Learning Points
- Diagnosis of cyclical Cushing can be very challenging. Late-night salivary cortisol is more reliable than 24-hour urinary cortisol.
- The paradoxical rise in cortisol in the Liddle test is confirmatory for cyclical Cushing, hence the testing should be considered early in affected patients.
- Genetic testing assessing for Carney complex, PRAKA1A pathogenic variant, should be considered early in a patient with concern for cyclical Cushing and another system involved like testicular lesions.
- Although bilateral adrenalectomy is the recommendation for PPNAD; in selected patients, unilateral adrenalectomy might provide several years of remission.
Acknowledgements
Thank you to Dr. Hong Wang, MD, PhD, DABMGG, FACMG, FCCMG, for her support on this project and in all things. Thank you to Dr. Andre Lacroix MD, FCAHS, for reviewing the preoperative CT adrenals with the team.
Contributors
All authors made individual contributions to authorship. F.B. was involved in the diagnosis and management of the patient. N.S. was responsible for the patient’s surgery. C.J.Z. was involved in the patient’s surgery and postoperative care. R.S., M.S., and P.W. were all medical professionals involved in his management and care. All authors contributed, reviewed, and approved the final draft.
Funding
No public or commercial funding.
Disclosures
None declared.
Informed Patient Consent for Publication
Signed informed consent obtained directly from the patient’s relatives or guardians
Data Availability Statement
Data sharing is not applicable to this article as no datasets were generated or analyzed during the current study.
Author notes
Natashia Seemann and Funmbi Babalola co-senior author.
Filed under: adrenal, Cushing's, Rare Diseases | Tagged: adrenalectomy, Carney Complex, cyclic, pediatric, PPNAD, Primary pigmented nodular adrenocortical disease, PRKAR1A, remission, unilateral adrenalectomy | Leave a comment »
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