Pachydermoperiostosis Due to a Novel <i>HPGD</i> Splicing Site Mutation Masquerading as Acromegaly

Hypertrophic osteoarthropathy (HOA: MIM 167100)) is classified into primary and secondary types. Primary HOA, also known as pachydermoperiostosis (PDP), is a rare genetic condition with distinct clinical features including digital clubbing, skin thickening, and periostosis. Secondary HOA often occurs as a paraneoplastic syndrome or is associated with systemic diseases. In this report, we present a 17-year-old male patient who initially presented with significant digital clubbing, enlarged hands and feet, and excessive sweating. Although the initial suspected diagnosis was acromegaly, the patient's plasma level of insulin-like growth factor 1 was normal and growth hormone levels suppressed to <1 ng/dL following oral glucose tolerance test. Whole exome sequencing followed by Sanger sequencing of leukocyte deoxyribonucleic acid revealed a novel splicing variant in the 15-hydroxyprostaglandin dehydrogenase (<i>HPGD</i>) gene (NM_000860.6: c.662 + 5_662 + 8del). Reverse transcription polymerase chain reaction confirmed that this variant led to defective splicing with skipping of exon 6, a frameshift, and truncation at codon 13 of exon 7 downstream. His symptoms did not respond well to nonsteroidal anti-inflammatory drugs but showed excellent response to a trial of lanreotide autogel that has been used for about 1 year.