Diagnosis of pseudo-gout (calcium pyrophosphate deposition disease) clinched on cytology

Calcium pyrophosphate dihydrate (CPPD) deposition disease is a metabolic arthropathy which results from deposition of calcium pyrophosphate crystals in and around joints especially the hyaline cartilage and disc material. This metabolic disease in uncommon in the smaller joints and multiple diagnostic modalities along with biochemical investigations would be necessary for definite diagnosis. We highlight the case of a 48 year old male who presented with a painful mass at the base of left thumb and was clinic-radiologically suspected as malignancy. Cytological examination (fine needle aspiration cytology [FNAC]) showed numerous extracellular rods shaped and rhomboid blunt-ended crystals along with foreign body type of giant cells. The main emphasis here is on the pivotal role played by FNAC in accurately diagnosing the disease where other modalities like radiology and histopathology failed to do so. The exact categorization of crystals is important from treatment point of view to avoid any major deformities in the joints/systemic manifestation.