Spontaneous Resolution of Unexplained Neutropenia in Primary Hyperparathyroidism: A Case Report.

A 65-year-old gentleman was referred to our institution through the two-week-wait pathway after presenting with a four-week history of bilateral lymphadenopathy. A lymph node biopsy confirmed the diagnosis of follicular lymphoma, grade III, for which he was treated with six cycles of obinutuzumab and bendamustine. A completion computed tomography scan showed stable appearances of the spleen and stranding in the left iliac chain. Obinutuzumab was continued as maintenance therapy. Despite the completion of lymphoma treatment and without evidence of disease relapse, he developed a persistent neutropenia, leading to recurrent chest infections and oesophageal candidiasis. He underwent multiple bone marrow biopsies to investigate further. During the same timeline, he was concurrently diagnosed with primary hyperparathyroidism (PHPT). Parathyroidectomy was performed following the recommendation from the Endocrine Multidisciplinary Team review, after initial delays due to concerns about operating while neutropenic. Following parathyroidectomy, the hypocalcaemia-related symptoms resolved, and the serum calcium and parathyroid hormone (PTH) levels have returned to normal. Notably, a complete restoration of the neutropenia was observed, along with the recovery of chronic persistent respiratory infections. This case highlights that isolated neutropenia can also be associated with PHPT, providing further evidence, in addition to existing research and similar case reports, that have focused more on anaemia and pancytopenia. Therefore, we recommend investigating refractory neutropenia or pancytopenia with bone profiles, including calcium, phosphate, and PTH levels. Early identification of hyperparathyroidism and prompt referral to the Endocrinology Team can be critical, as surgical intervention can lead to a complete recovery of neutropenia.