A Case of Calcium Pyrophosphate Deposition in Extra Articular Soft Tissue

A 52 year old male presents with a history of TBI, lumbar/cervical disk degeneration, and progressive radiculopathy for the past 2 years. Patient reports, in the last 2 years he has digressed from being able to walk without assistance to needing a wheelchair for long distances and a walker for short distances. He noticed a mass on the medial aspect of his hallux about 4 months prior to his first visit. Over the last 2-3 months, it became painful to walk on. Conservative treatments failed. Initial differential diagnosis included; granuloma, neuroma, ganglion cyst.  No mass was identified on X-ray. A right foot MRI with contrast was performed utilizing: T1, T1 fat saturation, T2, T2 fat saturation, STIR sequences, gadolinium weighted sequences. Within the plantar soft tissues, subjacent and distal to the medial sesamoid bone a well-circumscribed ovoid 1.0×1.3×0.9 cm mass was present on the T1/T2 sequences. The mass was heterogeneous with low signal intensity on T1. On T2, the mass primarily demonstrated decreased signal intensity centrally with a small focus of increased T2 signal intensity at the mid medial margin. Excisional biopsy was recommended because malignancy could not be completely excluded. The mass was removed in the operating room under MAC and local anesthesia. The terminal branch of the medial plantar nerve was involved with the mass and had to be resected with the mass. A satellite lesion was also found and excised as well. The 1st MPJ joint was noted to not be involved. All specimens were sent to pathology for further examination. Microscopic exam identified that the mass was consistent with pseudogout deposition or CPPD with embedded nerve tissue. The etiology of the mass was unknown. After performing a literature review, no previous reports described CPPD outside of a joint involving nervous tissue. Reports on tumoral calcinosis were the closest description found in the literature possibly explaining the mass found in this case. The etiology of the mass is unknown and may be secondary to minor traumas experienced during his time as a paratrooper or a adverse effect of the progressive radiculopathy.

Trademarked Items (if applicable):

References (if applicable): 1. Olsen, K. M., & Chew, F. S. (2006). Tumoral Calcinosis: Pearls, Polemics, and Alternative Possibilities. RadioGraphics, 26, 871-885.
2. Rosenthal, A. K., & Ryan, L. M. (2016). Calcium Pyrophosphate Deposition Disease. New England Journal of Medicine, 374(26), 2575-2584.