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Primary pigmented nodular adrenocortical disease
Primary pigmented nodular adrenocortical disease (PPNAD) is a form of bilateral adrenocortical hyperplasia that is often associated with adrenocorticotrophin hormone (ACTH) independent Cushing syndrome (see this term) and is characterized by small to normal sized adrenal glands containing multiple small cortical pigmented nodules (less than 1 cm in diameter).
ORPHA:189439Classification level: Disorder
The prevalence of endogenous Cushing syndrome (CS; see this term) is estimated at 1/26,000. PPNAD is responsible for less than 2% of cases. PPNAD is more frequent in females, especially after puberty.
Although the majority of cases are diagnosed in the 2nd and 3rd decades of life, a substantial proportion of patients present during early childhood (2-3 years). Patients with PPNAD often present with atypical CS, which is characterized by an asthenic, rather than obese, body habitus caused by severe osteoporosis, short stature and severe muscle and skin wasting. Patients with atypical CS have normal or near normal 24-hour urinary free cortisol production, but this is characterized by the absence of the normal circadian rhythmicity of cortisol. In adolescents and children with PPNAD, the disease frequently presents with periodic CS in which normal cortisol production is interrupted by days or weeks of hypercortisolism.
More than 90% of reported cases of PPNAD occur as one of the manifestations of Carney complex (CNC; see this term). Although rare, familial cases of isolated PPNAD have also been reported. The condition is inherited in an autosomal dominant manner and can be associated with mutations in the PRKAR1A, PDE11A and PDE8B genes.
Diagnosis is first based on confirmation of hypercortisolism (24hr urinary free cortisol, late night salivary cortisol, low-dose and high-dose dexamethasone-suppression test and assessment of midnight plasma cortisol). The second step is plasma ACTH detection to distinguish ACTH-independent CS (values lower than 5-10 pg/ml) from ACTH-dependent CS (see these terms). In some cases, nodules are visible on adrenal gland computed tomography (CT) or magnetic resonance imaging (MRI). The combination of atrophy and nodularity gives the glands an irregular contour, which is distinctly abnormal and diagnostic, especially in younger patients. Patients with PPNAD should also be screened for CNC and its potentially serious components.
Differential diagnoses are ACTH-dependent CS, including pituitary (Cushing disease) or extra-pituitary tumors (ectopic ACTH secretion) and the other causes of ACTH-independent CS including adrenal adenoma and carcinoma (see these terms).
Genetic testing for mutations of PRKAR1A, PDE11A and PDE8B genes may be discussed to detect affected patients in families with identified mutations. Genetic counseling may be offered in families with these mutations.
Management and treatment
Bilateral adrenalectomy is the most common treatment for CS due to PPNAD followed by life-long cortisol and mineralocorticoid supplementation.
Without treatment, CS due to PPNAD can be life-threatening.