MON-075 - A rare case of Castleman Disease and Infundibuloneurohypophysitis (INPH)

Introduction:
Infundibuloneuro-hypophysitis (INPH) is a rare form of hypophysitis, accounting for only 10% of cases. Its most common clinical features are polyuria and polydipsia due to Arginine Vasopressin (AVP) deficiency. INPH has been associated with various systemic conditions, including lymphoproliferative disorders, autoimmune neurohypophysitis, and granulomatous diseases. The association between hypophysitis and Castleman’s disease, particularly in conjunction with POEMS syndrome, is exceptionally rare, with only one prior case report describing hypopituitary symptoms in a patient with Castleman’s disease and hypophysitis. We present a case of INPH in a patient with coexisting Castleman’s disease, lupus, and a history of treated latent Mycobacterium tuberculosis infection.

Case:
A 60-year-old male presented to our Endocrine Clinic for evaluation of incidental chronic fatigue, low libido, and erectile dysfunction. He was initially diagnosed with plasma cell variant, HIV/HHV-8 negative multicentric Castleman’s disease over 10 years ago and received a short course of Rituximab and steroids with a partial response. Rituximab was discontinued due to new-onset heart failure. POEMS syndrome was excluded, given the absence of polyneuropathy and monoclonal plasma cell disorder. He also has a diagnosis of SLE with ANA+, dsDNA+, and is currently maintained on Leflunomide therapy. The patient completed a course of Isoniazid for 9 months for latent TB. During the follow-up for Castleman's disease, he was found to have increased cervical lymphadenopathy. The CT scan of head and neck revealed pituitary enlargement, which was confirmed with pituitary MRI. Repeat MRI 4 months showed similar findings: pituitary stalk thickening of 5.5 mm with loss of posterior pituitary bright spot and no mass effect or progression, diagnosed with infundibulo-neurophypophysitis. The patient denied polyuria and polydipsia, and sodium remained stable ranging from 138-142. The hormonal work up showed growth hormone deficiency with IGF-1 32 ng/mL (-2.5 SD) age adjusted, hypogonadotrophic hypogonadism, with FSH 2.55 mIU/mL (1.5-12.4), LH 3.8 mIU/mL (1.7-8.6) and Total Testosterone 136 ng/dL (264-916), Free Testosterone 21.5 pg/mL (35-155). Prolactin, cortisol, ACTH, and thyroid function was normal.

Conclusion:
This is a unique case of INPH with multiple etiologies. Differential diagnosis for this case is broad, including autoimmune/ inflammatory, lupus-related, Castleman’s disease, and Granulomatous disease. To our knowledge, this is the second case reported for hypophysitis associated with Castleman’s disease and the first case without the POEMS syndrome. Given stable imaging and no mass effect, the biopsy was deferred. Management includes regular pituitary hormone monitoring, replacement, and pituitary MRI. We may consider a pituitary biopsy if there is disease progression.

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