Myxedema coma, a rare but fatal emergency, is an extreme expression of hypothyroidism. We describe a 51-year-old male patient who has discontinued hypothyroidism treatment 10 months earlier and developed lethargy, edema, and cold intolerance symptoms. He also had a previous diagnosis of neurofibromatosis. After admission, he progressed to respiratory insufficiency and coma. The prompt recognition of the condition, thyroid hormone replacement, and management of the complications (hypoventilation, cardiogenic shock associated with swinging heart, adrenal and renal insufficiency and sepsis), resulted in a favorable evolution.579743747Kwaku, M.P., Burman, K.D., Myxedema coma (2007) J Intensive Care Med, 22, pp. 224-231Wartofsky, L., Myxedema coma (2000) The Thyroid: A Fundamental and Clinical Text, p. 843. , Braverman LE, Utiger RD (eds.). Philadelphia Lippincott: Williams & WilkinsDutta, P., Bhansali, A., Masoodi, S., Bhadada, S., Sharma, N., Rajput, R., Predictors of outcome in myxedema coma: A study from a tertiary care centre (2008) Critical Care, 12, pp. S1Rodríguez, I., Fluiters, E., Pérez-Méndez, L.F., Luna, R., Páramo, C., García-Mayor, R.V., Factors associated with mortality of patients with myxoedema coma: Prospective study in 11 cases treated in a single institution (2004) J Endocrinol, 180, pp. 347-350Kearney, T., Dang, C., Diabetic and endocrine emergencies (2007) Postgrad Med J, 83, pp. 79-86Danilovic, D.L.S., Almeida, M.Q., Neto, R.A.B., Martins, H., Coma Mixedematoso (2012) Emergências Clinicas Abordagem Prática, pp. 974-980. , 7th Ed. Barueri: ManoleSantiago, R., Rashkin, M.C., Lithium toxicity and myxedema coma in an elderly woman (1990) J Emerg Med, 8, p. 63Park, C.W., Shin, Y.S., Ahn, S.J., Kim, S.Y., Choi, E.J., Chang, Y.S., Thyroxine treatment induces upregulation of renin-angiotensin-aldosterone system due to decreasing effective plasma volume in patients with primary myxoedema (2001) Nephrol Dial Transplant, 6, pp. 1799-1806Klubo-Gwieedzinska, J., Wartofsky, L., Thyroid emergencies (2012) Med Clin N Am, 96, pp. 385-403Villabona, C., Sahun, M., Roca, M., Mora, J., Gomez, N., Gomez, J.M., Blood volumes and renal function in overt and subclinical primary hypothyroidism (1999) Am J Med Sci, 318, p. 27280Iwasaki, Y., Oiso, Y., Yamauchi, K., Osmoregulation of plasma vasopressin in myxedema (1990) J Clin Endocrinol Metab, 70, pp. 534-539Barker, D., Wright, E., Nguyen, K., Cannon, L., Fain, P., Goldgar, D., Gene for von Recklinghausen neurofbromatosis is in the pericentromeric region of chromosome 1 7 (1987) Science, 236, pp. 1100-1102Abbas, A., Lichtman, A.H., Disease caused by immune responses: Hipersensitivity and autoimmunity (2005) Cellular and Molecular Immunology, pp. 411-431. , Abbas A, Lichtman AH, eds., 5th ed. Philadelphia: SaundersYalcin, B., Tamer, E., Gür, G., Oztas, P., Polat, M.U., Alli, N., Neurofibroma-tosis 1/Noonan syndrome associated with Hashimoto's thyroidi-tis and vitiligo (2006) Acta Derm Venereol, 86, pp. 80-81Nanda, A., Autoimmune diseases associated with neurofibromato-sis type 1 (2008) Ped Dermatology, 25 (3), pp. 392-393Mackerrow, S.D., Osborn, L.A., Levy, H., Eaton, R.P., Economou, P., Myxedema-associated cardiogenic shock treated with intravenous triiodothyronine (1992) Ann Intern Med, 117, pp. 1014-1015