Primary hypertrophic osteoarthropathy due to a novel SLCO2A1 mutation masquerading as acromegaly

Summary

A 20-year-old man with an 8-year history of progressive enlargement of his hands and feet, coarsening facial features, painful joints and thickened, oily skin was referred for investigation of acromegaly. On examination, the subject was of normal height and weight. He had markedly increased skin thickness around the forehead, eyelids and scalp with redundant skin folds. Bilateral painful knee swelling was accompanied by enlargement of the extremities, and his fingers were markedly clubbed. Routine hematological, biochemical and hormonal blood tests, including GH and IGF-1 were normal. The clinical picture suggested primary hypertrophic osteoarthropathy (PHOA) rather than acromegaly and radiological studies were supportive of this, demonstrating increased subperiosteal bone formation and increased bone density and cortical thickening. There was widespread joint disease, with narrowing of joint spaces, whereas the knees demonstrated effusions and calcification. A skull X-ray revealed calvarial hyperostosis and a normal sellar outline. Family history was negative. Genetic studies were performed on peripheral blood leukocyte DNA for mutations in the two genes associated with PHOA, 15-hydroxyprostaglandin dehydrogenase (HPGD; OMIM: 601688) and solute carrier organic anion transporter family member 2A1 (SLCO2A1; OMIM: 601460). The sequence of HPGD was normal, whereas the subject was homozygous for a novel pathological variant in SLCO2A1, c.830delT, that predicted a frameshift and early protein truncation (p.Phe277Serfs*8). PHOA, also known as pachydermoperiostosis, is a rare entity caused by abnormal prostaglandin E2 metabolism, and both HPGD and SLCO2A1 are necessary for normal prostaglandin E2 handling. High prostaglandin levels lead to bone formation and resorption and connective tissue inflammation causing arthropathy, in addition to soft tissue swelling.

Learning points:

Combined treatment with octreotide LAR and pegvisomant in patients with pituitary gigantism: clinical evaluation and genetic screening

INTRODUCTION

Pituitary gigantism is a rare condition caused by growth hormone secreting hypersecretion, usually by a pituitary tumor. Acromegaly and gigantism cases that have a genetic cause are challenging to treat, due to large tumor size and poor responses to some medical therapies (e.g. AIP mutation affected cases and those with X-linked acrogigantism syndrome).

MATERIALS AND METHODS

We performed a retrospective study to identify gigantism cases among 160 somatotropinoma patients treated between 1985 and 2015 at the University Hospital of Caracas, Venezuela. We studied clinical details at diagnosis, hormonal responses to therapy and undertook targeted genetic testing. Among the 160 cases, eight patients (six males; 75 %) were diagnosed with pituitary gigantism and underwent genetic analysis that included array comparative genome hybridization for Xq26.3 duplications.

RESULTS

All patients had GH secreting pituitary macroadenomas that were difficult to control with conventional treatment options, such as surgery or primary somatostatin receptor ligand (SRL) therapy. Combined therapy (long-acting SRL and pegvisomant) as primary treatment or after pituitary surgery and radiotherapy permitted the normalization of IGF-1 levels and clinical improvement. Novel AIP mutations were the found in three patients. None of the patients had Xq26.3 microduplications.

CONCLUSIONS

Treatment of pituitary gigantism is frequently challenging; delayed control increases the harmful effects of GH excess, such as, excessive stature and symptom burden, so early diagnosis and effective treatment are particularly important in these cases.