Diagnosis by serendipity: Cushing syndrome attributable to cortisol-producing adrenal adenoma as the initial manifestation of multiple endocrine neoplasia type 1 due to a rare splicing site MEN1 gene mutation.

OBJECTIVE

To report a case that highlights the potential for Cushing syndrome to be the first manifestation of multiple endocrine neoplasia type 1 (MEN 1) syndrome and to describe the rare underlying genetic mutation and the heterogeneous manifestations of the syndrome within the same family.

METHODS

We present a case report including biochemical and radiologic findings, review family data, and discuss the results of genetic analyses.

RESULTS

A 16-year-old girl who was not known to have any medical illness and had no known family history of MEN 1 syndrome presented with Cushing syndrome attributable to a cortisol-producing adrenal adenoma. During her evaluation, she was found to have primary hyperparathyroidism and a pituitary microprolactinoma. These findings raised the possibility of MEN 1 syndrome. She did not have clinical, biochemical, or radiologic evidence of islet cell pancreatic tumors. Family screening showed that her father had evidence of primary hyperparathyroidism, mild hyperprolactinemia, normal findings on magnetic resonance imaging of the pituitary, and a 1.2-cm nodule in the tail of the pancreas in conjunction with slight elevation of serum insulin and normal gastrin levels. The patient's 5 siblings had evidence of primary hyperparathyroidism, and 2 of them also had mild hyperprolactinemia. Genetic screening confirmed the presence of a MEN1 gene missense G to A mutation in the patient, her father, and her siblings at the splicing site of intron 6 (IVS6+1G>A). This mutation leads to frameshift and truncation of the MEN1 gene.

CONCLUSION

In MEN 1, Cushing syndrome is an extremely rare and usually late manifestation. Most cases are due to corticotropin-producing pituitary adenomas. Although Cushing syndrome generally develops years after the more typical manifestations of MEN 1 appear, it may be the primary manifestation of MEN 1 syndrome. There is considerable heterogeneity in the manifestations of MEN 1, even within a family having the same genetic mutation.