Forty four years old, single, unemployed male patient with paranoid schizophrenia and congenital myotonia has been presented in this case report. He was hospitalized because of collecting garbages, hostility toward his brothers, fattening many animals, living in very dirty surroundings. His mother was treated as bipolar disorder.

He had muscular disease since childhood, weakness began initially in arms then in legs. There is muscular weakness in both of the proximal and distal extremities. He presented with dirty, old attire. He was indifferent and had flattened affect. His behaviors were bizarre. He made poor eye contact. He had no insight. He was in defensive attitude. There was no hallusinations. He had severe persecutive delusions toward his brothers. Generalized muscular disease with myotonic decharges was diagnoses in EMG. Olanzapine,20mg/day was applied. The patient responded to the medication and the psycotic symptoms were totally disappeared.

It is known that central serebral system may be effected and hypodense areas are seen in the brains of Thomsen type congenital muscular dystrophy which is comorbid with mental retardation (Kamoshıta et al 1963). We assume that an unspecified disorder in the central serebral system might be presented as paranoid schizophrenia in this patient with congenital myotonia and there may be some common aspects among both of these illnesses.