Cryoglobulins (CGs) are immunoglobulins that precipitate in the blood under cold conditions (<37◦ C) and redissolve upon warming¹.  The term “cryoglobulinemia” is commonly used to describe patients with a systemic inflammatory syndrome that is often associated with small-to-medium vessel vasculitis due to cryoglobulin-containing immune complexes. Although some patients with cryoglobulinemia may be asymptomatic, most present with a range of diseases characterized by fatigue, arthralgia, skin rashes or necrosis, purpura, neuropathy, bowel wall ischemia and/or glomerulonephritis and kidney failure.

Wintrobe and Buell are credited for first describing cryglobulinemia in 1933 when assessing a patient who ultimately was found to have multiple myeloma². Since then the spectrum of diseases associated with CG has expanded to also include seemingly disparate conditions such as hepatitis C, autoimmune disorders and monoclonal gammopathy of undetermined significance (MGUS).  A commonly cited classification scheme for CG is shown (Table)³.   It should be emphasized that some CGs may not fit neatly into this scheme.

In our patient, the positive CG serum test should be interpreted in the clinical context in which it was obtained while searching for risk factors as well as signs and symptoms that may be associated with cryoglobulinemia.

Table. Classification of cryoglobulinemia

References

1. Takada S, Shimizu T, Hadano Y, et al. Cryoglobulinemia (review). Mol Med Rep 2012;6:3-8
2. Wintrobe MM, Buell MV. Hyperproteinemia associated with multiple myeloma. Bull Johns Hopkins Hosp 52: 156-165, 1933
3. Brouet JC, Clauvel JP, Danon F, et al. Biological and clinical significance of cryoglobulins. Am J Med 1974; 57:775-88.

Contributed by Kirstin Scott, Medical Student, Harvard Medical School