• Young man presents with fever, erythema nodosum (painful, red, tender nodules on anterior shins) and bilateral hilar fullness, most consistent with sarcoidosis
• Key idea: Sarcoidosis (like other forms of granulomatous disease) is associated with hypercalcemia because of increased activity of 1-alpha hydroxylase leading to increased production of activated vitamin D –> hypercalcemia, hyperphosphatemia
• Ddx for erythema nodosum: Sarcoidosis, Strep infections, tuberculosis, inflammatory bowel disease, Behcet disease, endemic fungal disease (cocci, histo)
• Key idea: If patient has erythema affecting both legs, then cellulitis is virtually ruled out! (bilateral cellulitis very rare)

https://step-prep.org/tutoring/