Table 1.

Proposed classification of CSH

According to etiology and/or associated disease	According to crystal
1. Hematopoietic	1. Immunoglobulin
A. Multiple myeloma	A. Type
B. Extramedullary plasmacytoma	(1) Heavy chain
C. Lymphomas	(2) Light chain
	B. Clonality
2. MGUS-Amyloid	(1) Monoclonal
	(2) Polyclonal
3. Drugs	(3) Indeterminate
A. Clofazimine
	2. Clofazimine
4. Allergic-autoimmune
A. Rheumatoid arthritis	3. Charcot-Leyden
B. Eosinophilic colitis
C. Mastocytosis	4. Other
D. Hypereosinophilic syndrome	A. Cystine
	B. Silica
5. Metabolic
A. Cystinosis
6. Inflammatory-reactive
A. Pulmonary infections
B. Plasma cell granuloma
C. Crohn’s disease
D. Helicobacter pylori
7. Other
A. Silica

CSH crystal-storing histiocytosis, MGUS monoclonal gammopathy of undetermined significance