Pachydermoperiostosis: A Rare Masquerader of Acromegaly and Thyroid Acropachy

Background: Pachydermoperiostoasis is a rare disease of prostaglandin metabolism that presents with extensive clubbing, skin thickening, and enlargement of hands and feet, often misdiagnosed as acromegaly or thyroid acropachy. Clinical Case: A 29-year-old male presented with progressive enlargement of hands and feet for the past three years, with increased sweating, seborrhea, acne, arthralgia, and photophobia. On examination, facial furrowing and severe clubbing in all fingers and toes was noticed, with palmoplantar hyperhidrosis, tenderness and widening around distal forearms, and increased heel pad thickness. He had nodulocystic acne, injected right eye with ptosis, normal pupil, and visual field. Slit-lamp examination showed extensive pannus formation, with yellow nodules, suggestive of phlyctenular conjunctivitis, secondary to a systemic inflammatory process. No prominent supraorbital ridge, prognathism, proptosis, goiter, or pretibial myxedema. No family history of a similar condition. Labs showed normal cell counts and metabolic panel. Normal IGF-1 (112 ng/mL, n 84-250 ng/ml), TSH (3.82 mIU/L, n 0.27-4.2 mIU/L), fT4 (1.19 ng/dL, n 0.93-1.7 ng/dL), Testosterone (354 ng/dL, n 249-836 ng/dL) and Prolactin (15.2 ng/mL, n 2.1-17.7 ng/mL). Inflammatory markers were elevated with ESR of 54 mm/hr (n 0-15 mm/hr) and CRP of 12.45 mg/L (n 1-4 mg/L). ANA, RF, anti-CCP, and HLA-B27 were negative. C3 and C4 levels were normal as well. Interferon-gamma release assay was negative. Imaging showed a normal chest X-ray. Brain MRI showed normal pituitary gland and increased scalp skin thickness with cutis verticis gyrata “undulating skin sign.” X-ray of hands and feet showed diffuse periosteal reaction. A diagnosis of pachydermoperiostosis (PDP) was made based on clinical criteria (thickened skin, periosteal reaction, and finger clubbing). PDP is a genetic disorder of prostaglandin metabolism with variable expression and incomplete penetrance. It manifests after puberty and affects males more than females with a 7:1 ratio. PDP has been recently shown to go through an inflammatory phase, in which patients may benefit from immunosuppressants or NSAIDs. PDP should be distinguished from hypertrophic pulmonary osteoarthropathy, thyroid acropachy, and acromegaly. Our patient had a normal chest radiograph and normal hormone levels (TSH, T4, and IGF-1). The patient received topical steroids and antibiotics with artificial tears for his eyes, which resulted in a good response, and was referred to a rheumatology clinic for further management. Clinical Lesson: PDP can be mistaken for acromegaly or thyroid acropachy and should be considered in any patient with acromegaloid features with normal IGF-1 and no evident pituitary pathology. Awareness of this condition can help in reaching the diagnosis promptly.