Clinical Description
The Carney complex (CNC) of skin pigmentary abnormalities, myxomas, endocrine tumors or overactivity, and schwannomas may be evident at birth, although the median age of diagnosis is 20 years. To date, more than 750 individuals have been identified with a pathogenic variant in PRKAR1A. The following description of the phenotypic features associated with this condition is based on these reports.
Table 2.
Carney Complex: Frequency of Select Features
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Feature | % of Persons w/Feature | Comment |
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Skin pigment abnormalities | >70% | |
Myxomas (cutaneous & mucosal) | >50% | |
Cardiac myxoma | 30%-50% | |
Breast myxoma | 30%-50% | |
PPNAD | ~25% | |
Somatomammotroph hyperplasia / GH-producing adenoma | ≤75% | |
LCCSCT | >50% of males | |
Thyroid tumor(s) | ≤75% | Mostly nonfunctioning thyroid follicular adenomas |
PMS | ~10% | |
LCCSCT = large cell calcifying Sertoli cell tumor; GH = growth hormone; PMS = psammomatous melanotic schwannoma; PPNAD = primary pigmented nodular adrenocortical disease
Skin pigment abnormalities
Pale brown to black lentigines are the most common presenting feature of CNC and may be present at birth. Typically, they increase in number and appear anywhere on the body, including the face, the lips, and mucosa around puberty. These lentigines tend to fade after the fourth decade but may still be evident in the eighth decade.
Additional pigmentary abnormalities that develop over time are epithelioid-type blue nevi (small, bluish, domed papules with a smooth surface), combined nevi, café au lait macules, and depigmented lesions.
Myxomas
Cutaneous myxomas are papules or subcutaneous nodules that usually have a smooth surface and are white, flesh-colored, opalescent, or pink. They appear between birth and the fourth decade. Most individuals with CNC have multiple lesions. Myxomas occur on any part of the body except the hands and feet and typically affect the eyelids, external ear canal, and nipples.
Cardiac myxomas occur at a young age and may occur in any or all cardiac chambers. Cardiac myxomas present with symptoms related to intracardiac obstruction of blood flow, embolic phenomenon (into the systemic circulation), and/or heart failure. Myxomas that completely occlude a valvular orifice can cause sudden death.
Breast myxomas, often bilateral, occur in females after puberty. Both males and females may develop nipple myxomas at any age.
Other sites for myxomas include the oropharynx (tongue, hard palate, pharynx) and the female genital tract (uterus, cervix, vagina).
Osteochondromyxoma is a rare myxomatous tumor of the bone that affects nasal sinuses and long bones.
Endocrine tumors
Primary pigmented nodular adrenocortical disease (PPNAD) is associated with adrenocorticotropic hormone (ACTH)-independent overproduction of cortisol (hypercortisolism). PPNAD is the most frequently observed endocrine tumor in individuals with CNC. In a minority of individuals, PPNAD presents in the first two to three years; in the majority, it presents in the second or third decade. The hypercortisolism of PPNAD is usually insidious in onset. In children, hypercortisolism is manifest first as weight gain and growth arrest. In adults, long-standing hypercortisolism results in Cushing syndrome with central obesity, "moon facies," hirsutism, striae, hypertension, buffalo hump fat distribution, weakness, easy bruising, and psychological disturbance. Cushing syndrome is seen in 70% of affected females before age 45 years but in only 45% of affected males, similar to the higher frequency of Cushing syndrome in females in general. Histologic evidence of PPNAD has been found in almost every individual with CNC undergoing autopsy.
Growth hormone (GH)-producing pituitary adenomas. Clinically evident acromegaly is a relatively frequent manifestation of CNC, occurring in approximately 10% of adults at the time of presentation. Gigantism, resulting from excess GH secretion prior to puberty, is rare. However, asymptomatic increased serum concentration of GH and insulin-like growth factor 1 (IGF-1), as well as subtle hyperprolactinemia, may be present in up to 75% of individuals with CNC. Somatomammotroph hyperplasia, a putative precursor of GH-producing adenoma, may explain the protracted period of onset of clinical acromegaly in individuals with CNC.
Thyroid adenoma or carcinoma. Up to 75% of individuals with CNC have multiple thyroid nodules, most of which are nonfunctioning thyroid follicular adenomas. Thyroid carcinomas, both papillary and follicular, can occur and occasionally may develop in a person with a long history of multiple thyroid adenomas.
Testicular tumors. Large cell calcifying Sertoli cell tumors (LCCSCTs) are observed in one third of affected males at the time of presentation, which is often within the first decade. Most adult males with CNC have evidence of LCCSCTs. The tumors are often multicentric and bilateral. LCCSCTs are almost always benign; malignancy has been reported only once, in an individual age 62 years. LCCSCTs may be hormone producing; gynecomastia in prepubertal and peripubertal boys may result from increased P-450 aromatase expression. Other testicular tumors observed in individuals with LCCSCTs include Leydig cell tumors and (pigmented nodular) adrenocortical rest tumors.
Ovarian cancer can rarely be present in CNC, often developing in the background of chronic and large multiplex ovarian cysts.
Psammomatous melanotic schwannoma (PMS). This rare tumor of the nerve sheath occurs in approximately 10% of individuals with CNC. Malignant degeneration occurs in approximately 10% of PMS in those with CNC [Watson et al 2000]. PMS may occur anywhere in the central and peripheral nervous system; it is most frequently found in the nerves of the gastrointestinal tract (esophagus and stomach) and paraspinal sympathetic chain (28%). The spinal tumors present as pain and radiculopathy in adults (mean age 32 years).
Pancreatic tumors with various histology (e.g., adenocarcinoma, acinar cell carcinoma, intraductal papillary mucinous neoplasm) were found in 2.5% (9/354) of individuals from an international CNC registry.
Breast ductal adenoma is a benign tumor of the mammary gland ducts. It may be seen in individuals with CNC, although exact data about its frequency are lacking.
Life span. Most individuals with CNC have a normal life span. However, because some die at an early age, the average life expectancy for individuals with CNC is 50 years. Causes of death include complications of cardiac myxoma (myxoma emboli, cardiomyopathy, cardiac arrhythmia, surgical intervention), metastatic or intracranial PMS, thyroid carcinoma, and metastatic pancreatic and testicular tumors.
Fertility. LCCSCTs cause replacement and obstruction of seminiferous tubules, macroorchidism, oligoasthenospermia, and inappropriate hormone production or aromatization. Despite these findings, fertility is frequently preserved.
Milder phenotypes. Most individuals with CNC meet diagnostic criteria. Very rarely, individuals may present with one clinical feature without any additional manifestations. These individuals can present with PPNAD or acromegaly only.
Penetrance
The overall penetrance of CNC in those with a PRKAR1A pathogenic variant is greater than 95% by age 50 years.
To date only two PRKAR1A pathogenic variants are known to result in incomplete penetrance of CNC: the splice site variant c.709-7_709-2delTTTTTA and the initiation-alternating substitution c.1A>G (p.Met1Val). When expressed, these two pathogenic variants lead to relatively mild CNC, manifesting mostly as PPNAD, which can be accompanied by lentigines [Groussin et al 2006].
Nomenclature
Carney complex has also been designated by the following acronyms:
NAME (nevi, atrial myxomas, ephelides)
LAMB (lentigines, atrial myxoma, blue nevi)
"Carney triad" (OMIM 604287) is a completely different entity consisting of a triad of gastrointestinal stromal tumors, pulmonary chondroma, and extra-adrenal paraganglioma.