Which of the following signs is indicative of homocystinuria?

• A. Pectus excavatum
• B. Butterfly rash
• C. Facial telangiectasias
• D. Thickened skin

Answer: (A)

Homocystinuria is a genetic condition that leads to an accumulation of homocysteine due to deficiencies in specific enzymes involved in the metabolism of this amino acid. One of the characteristic signs associated with homocystinuria is pectus excavatum, which refers to a developmental deformity of the chest wall where the sternum is abnormally sunk in or caved in. This condition is part of the spectrum of physical findings often seen in patients with homocystinuria, along with other features such as long limbs, myopia, and a predisposition to thromboembolism.

The presence of pectus excavatum in a patient suspected of having homocystinuria may serve as an important clinical clue for diagnosis, linking the symptom to the underlying metabolic disorder. In contrast, the other options—such as a butterfly rash, which is typically associated with systemic lupus erythematosus, facial telangiectasias seen in conditions like rosacea or hereditary hemorrhagic telangiectasia, and thickened skin which may be indicative of systemic sclerosis or other dermatological conditions—do not correlate with homocystinuria.

Thus, identifying pectus excavatum as indicative of hom