Mothball ingestion as a manifestation of pica, leading to paradichlorobenzene CNS toxicity

Background: Pica is a poorly understood psychiatric disorder that presents with the ingestion of non-nutritious substances for unclear reasons. A high index of suspicion for unusual toxin exposure aids in the diagnosis of pica patients presenting with unexplained neurodegenerative features.
Methods: We present a 47-year-old female with worsening gait over the past year. Prior to this, she was fully independent with activities of daily living, but is now mostly housebound due to frequent falls. Past medical history is significant for menorrhagia, iron deficiency anemia and pica. CBC and iron studies revealed iron deficiency with microcytic hypochromic anemia. MRI brain demonstrated symmetrical T2 hyperintensities within the middle cerebellar peduncles.
Results: Differential diagnoses for her clinical deficits and imaging, including Spinocerebellar Ataxia, Multiple System Atrophy and Fragile X Tremor-Ataxia Syndrome, were excluded based on neurological assessment, family history and genetic PCR testing. Collateral history revealed a regular habit of mothball ingestion and serum paradichlorobenzene levels were elevated to 15mcg/mL. The patient was treated with iron replacement therapy and her symptoms gradually improved over several months.
Conclusion: Iron deficiency anemia is commonly associated with pica, which can lead to toxin ingestion. A high index of suspicion for toxin ingestion in pica patients can immensely aid in the diagnosis. Mothball abuse secondary to pica may affect the CNS and can present with nonspecific neurodegenerative changes. To our knowledge, there have been no reported cases in the literature with paradichlorobenzene neurotoxicity predominantly affecting the middle cerebellar peduncles.

Keywords
Mothball; paradichlorobenzene; PDCB; toxicity; pica; middle cerebellar peduncles.